[RFC][PATCH 0/8] Suspend block api

[RFC][PATCH 0/8] Suspend block api

[Arve Hjønnevåg]

This patch series adds a suspend-block api that provides the same
functionality as the android wakelock api from my last patch series,
Android PM extensions (version 3). As requested, wake_lock has been
renamed to suspend_block(er), and timeout support has been separated
into its own patch.

--
Arve Hjønnevåg

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[PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

Adds /sys/power/request_state, a non-blocking interface that specifies
which suspend state to enter when no suspend blockers are active. A
special state, "on", stops the process by activating the "main" suspend
blocker.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/suspend-blockers.txt |   76 +++++++++
 include/linux/suspend_block.h            |   61 +++++++
 kernel/power/Kconfig                     |   10 ++
 kernel/power/Makefile                    |    1 +
 kernel/power/main.c                      |   62 +++++++
 kernel/power/power.h                     |    6 +
 kernel/power/suspend_block.c             |  257 ++++++++++++++++++++++++++++++
 7 files changed, 473 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/power/suspend-blockers.txt
 create mode 100755 include/linux/suspend_block.h
 create mode 100644 kernel/power/suspend_block.c

diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
new file mode 100644
index 0000000..743b870
--- /dev/null
+++ b/Documentation/power/suspend-blockers.txt
@@ -0,0 +1,76 @@
+Suspend blockers
+================
+
+A suspend_blocker prevents the system from entering suspend.
+
+If the suspend operation has already started when calling suspend_block on a
+suspend_blocker, it will abort the suspend operation as long it has not already
+reached the sysdev suspend stage. This means that calling suspend_block from an
+interrupt handler or a freezeable thread always works, but if you call
+block_suspend from a sysdev suspend handler you must also return an error from
+that handler to abort suspend.
+
+Suspend blockers can be used to allow user-space to decide which keys should
+wake the full system up and turn the screen on. Use set_irq_wake or a platform
+specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
+driver has resumed, the sequence of events can look like this:
+- The Keypad driver gets an interrupt. It then calls suspend_block on the
+  keypad-scan suspend_blocker and starts scanning the keypad matrix.
+- The keypad-scan code detects a key change and reports it to the input-event
+  driver.
+- The input-event driver sees the key change, enqueues an event, and calls
+  suspend_block on the input-event-queue suspend_blocker.
+- The keypad-scan code detects that no keys are held and calls suspend_unblock
+  on the keypad-scan suspend_blocker.
+- The user-space input-event thread returns from select/poll, calls
+  suspend_block on the process-input-events suspend_blocker and then calls read
+  on the input-event device.
+- The input-event driver dequeues the key-event and, since the queue is now
+  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
+- The user-space input-event thread returns from read. It determines that the
+  key should not wake up the full system, calls suspend_unblock on the
+  process-input-events suspend_blocker and calls select or poll.
+
+                 Key pressed   Key released
+                     |             |
+keypad-scan          ++++++++++++++++++
+input-event-queue        +++          +++
+process-input-events       +++          +++
+
+
+Driver API
+==========
+
+A driver can use the suspend block api by adding a suspend_blocker variable to
+its state and calling suspend_blocker_init. For instance:
+struct state {
+	struct suspend_blocker suspend_blocker;
+}
+
+init() {
+	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
+}
+
+Before freeing the memory, suspend_blocker_destroy must be called:
+
+uninit() {
+	suspend_blocker_destroy(&state->suspend_blocker);
+}
+
+When the driver determines that it needs to run (usually in an interrupt
+handler) it calls suspend_block:
+	suspend_block(&state->suspend_blocker);
+
+When it no longer needs to run it calls suspend_unblock:
+	suspend_unblock(&state->suspend_blocker);
+
+Calling suspend_block when the suspend blocker is active or suspend_unblock when
+it is not active has no effect. This allows drivers to update their state and
+call suspend suspend_block or suspend_unblock based on the result.
+For instance:
+
+if (list_empty(&state->pending_work))
+	suspend_unblock(&state->suspend_blocker);
+else
+	suspend_block(&state->suspend_blocker);
+
diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
new file mode 100755
index 0000000..7820c60
--- /dev/null
+++ b/include/linux/suspend_block.h
@@ -0,0 +1,61 @@
+/* include/linux/suspend_block.h
+ *
+ * Copyright (C) 2007-2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SUSPEND_BLOCK_H
+#define _LINUX_SUSPEND_BLOCK_H
+
+/* A suspend_blocker prevents the system from entering suspend when active.
+ */
+
+struct suspend_blocker {
+#ifdef CONFIG_SUSPEND_BLOCK
+	atomic_t            flags;
+	const char         *name;
+#endif
+};
+
+#ifdef CONFIG_SUSPEND_BLOCK
+
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
+void suspend_blocker_destroy(struct suspend_blocker *blocker);
+void suspend_block(struct suspend_blocker *blocker);
+void suspend_unblock(struct suspend_blocker *blocker);
+
+/* is_blocking_suspend returns true if the suspend_blocker is currently active.
+ */
+bool is_blocking_suspend(struct suspend_blocker *blocker);
+
+/* suspend_is_blocked can be used by generic power management code to abort
+ * suspend.
+ *
+ * To preserve backward compatibility suspend_is_blocked returns 0 unless it
+ * is called during suspend initiated from the suspend_block code.
+ */
+bool suspend_is_blocked(void);
+
+#else
+
+static inline void suspend_blocker_init(struct suspend_blocker *blocker,
+					const char *name) {}
+static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
+static inline void suspend_block(struct suspend_blocker *blocker) {}
+static inline void suspend_unblock(struct suspend_blocker *blocker) {}
+static inline bool is_blocking_suspend(struct suspend_blocker *bl) { return 0; }
+static inline bool suspend_is_blocked(void) { return 0; }
+
+#endif
+
+#endif
+
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 23bd4da..9d1df13 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -116,6 +116,16 @@ config SUSPEND_FREEZER
 
 	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
 
+config SUSPEND_BLOCK
+	bool "Suspend block"
+	depends on PM
+	select RTC_LIB
+	default n
+	---help---
+	  Enable suspend_block. When user space requests a sleep state through
+	  /sys/power/request_state, the requested sleep state will be entered
+	  when no suspend_blockers are active.
+
 config HIBERNATION
 	bool "Hibernation (aka 'suspend to disk')"
 	depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 720ea4f..29cdc9e 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -6,6 +6,7 @@ endif
 obj-$(CONFIG_PM)		+= main.o
 obj-$(CONFIG_PM_SLEEP)		+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
+obj-$(CONFIG_SUSPEND_BLOCK)	+= suspend_block.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o disk.o snapshot.o swap.o user.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
diff --git a/kernel/power/main.c b/kernel/power/main.c
index c9632f8..e4c6b20 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -22,6 +22,7 @@
 #include <linux/freezer.h>
 #include <linux/vmstat.h>
 #include <linux/syscalls.h>
+#include <linux/suspend_block.h>
 
 #include "power.h"
 
@@ -392,6 +393,9 @@ static void suspend_finish(void)
 
 
 static const char * const pm_states[PM_SUSPEND_MAX] = {
+#ifdef CONFIG_SUSPEND_BLOCK
+	[PM_SUSPEND_ON]		= "on",
+#endif
 	[PM_SUSPEND_STANDBY]	= "standby",
 	[PM_SUSPEND_MEM]	= "mem",
 };
@@ -540,6 +544,61 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 power_attr(state);
 
+/**
+ *	request_state - control system power state.
+ *
+ *	This is similar to state, but it does not block until the system
+ *	resumes, and it will try to re-enter the state until another state is
+ *	requested. Suspend blockers are respected and the requested state will
+ *	only be entered when no suspend blockers are active.
+ *	Write "on" to cancel.
+ */
+
+#ifdef CONFIG_SUSPEND_BLOCK
+static ssize_t request_state_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	char *s = buf;
+	int i;
+
+	for (i = 0; i < PM_SUSPEND_MAX; i++) {
+		if (pm_states[i] && (i == PM_SUSPEND_ON || valid_state(i)))
+			s += sprintf(s, "%s ", pm_states[i]);
+	}
+	if (s != buf)
+		/* convert the last space to a newline */
+		*(s-1) = '\n';
+	return (s - buf);
+}
+
+static ssize_t request_state_store(struct kobject *kobj,
+				   struct kobj_attribute *attr,
+				   const char *buf, size_t n)
+{
+	suspend_state_t state = PM_SUSPEND_ON;
+	const char * const *s;
+	char *p;
+	int len;
+	int error = -EINVAL;
+
+	p = memchr(buf, '\n', n);
+	len = p ? p - buf : n;
+
+	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
+		if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
+			break;
+	}
+	if (state < PM_SUSPEND_MAX && *s)
+		if (state == PM_SUSPEND_ON || valid_state(state)) {
+			error = 0;
+			request_suspend_state(state);
+		}
+	return error ? error : n;
+}
+
+power_attr(request_state);
+#endif /* CONFIG_SUSPEND_BLOCK */
+
 #ifdef CONFIG_PM_TRACE
 int pm_trace_enabled;
 
@@ -567,6 +626,9 @@ power_attr(pm_trace);
 
 static struct attribute * g[] = {
 	&state_attr.attr,
+#ifdef CONFIG_SUSPEND_BLOCK
+	&request_state_attr.attr,
+#endif
 #ifdef CONFIG_PM_TRACE
 	&pm_trace_attr.attr,
 #endif
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 46b5ec7..2414a74 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
 {
 }
 #endif
+
+#ifdef CONFIG_SUSPEND_BLOCK
+/* kernel/power/suspend_block.c */
+void request_suspend_state(suspend_state_t state);
+#endif
+
diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
new file mode 100644
index 0000000..b4f2191
--- /dev/null
+++ b/kernel/power/suspend_block.c
@@ -0,0 +1,257 @@
+/* kernel/power/suspend_block.c
+ *
+ * Copyright (C) 2005-2008 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/suspend.h>
+#include <linux/suspend_block.h>
+#include <linux/sysdev.h>
+#include "power.h"
+
+enum {
+	DEBUG_EXIT_SUSPEND = 1U << 0,
+	DEBUG_WAKEUP = 1U << 1,
+	DEBUG_USER_STATE = 1U << 2,
+	DEBUG_SUSPEND = 1U << 3,
+	DEBUG_SUSPEND_BLOCKER = 1U << 4,
+};
+static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
+module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
+
+#define SB_INITIALIZED            (1U << 8)
+#define SB_ACTIVE                 (1U << 9)
+
+static DEFINE_SPINLOCK(state_lock);
+static atomic_t suspend_block_count;
+static atomic_t current_event_num;
+struct workqueue_struct *suspend_work_queue;
+struct suspend_blocker main_suspend_blocker;
+static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
+static bool enable_suspend_blockers;
+
+bool suspend_is_blocked(void)
+{
+	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
+		return 0;
+	return !!atomic_read(&suspend_block_count);
+}
+
+static void suspend_worker(struct work_struct *work)
+{
+	int ret;
+	int entry_event_num;
+
+	enable_suspend_blockers = 1;
+
+retry:
+	if (suspend_is_blocked()) {
+		if (debug_mask & DEBUG_SUSPEND)
+			pr_info("suspend: abort suspend\n");
+		goto abort;
+	}
+
+	entry_event_num = atomic_read(&current_event_num);
+	if (debug_mask & DEBUG_SUSPEND)
+		pr_info("suspend: enter suspend\n");
+	ret = pm_suspend(requested_suspend_state);
+	if (debug_mask & DEBUG_EXIT_SUSPEND) {
+		struct timespec ts;
+		struct rtc_time tm;
+		getnstimeofday(&ts);
+		rtc_time_to_tm(ts.tv_sec, &tm);
+		pr_info("suspend: exit suspend, ret = %d "
+			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
+			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
+	}
+	if (atomic_read(&current_event_num) == entry_event_num) {
+		if (debug_mask & DEBUG_SUSPEND)
+			pr_info("suspend: pm_suspend returned with no event\n");
+		goto retry;
+	}
+abort:
+	enable_suspend_blockers = 0;
+}
+static DECLARE_WORK(suspend_work, suspend_worker);
+
+static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
+{
+	int ret = suspend_is_blocked() ? -EAGAIN : 0;
+	if (debug_mask & DEBUG_SUSPEND)
+		pr_info("suspend_block_suspend return %d\n", ret);
+	return ret;
+}
+
+static struct sysdev_class suspend_block_sysclass = {
+	.name = "suspend_block",
+	.suspend = suspend_block_suspend,
+};
+static struct sys_device suspend_block_sysdev = {
+	.cls = &suspend_block_sysclass,
+};
+
+/**
+ * suspend_blocker_init() - Initialize a suspend blocker
+ * @blocker:	The suspend blocker to initialize.
+ * @name:	The name of the suspend blocker to show in
+ *		/proc/suspend_blockers
+ */
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
+{
+	if (name)
+		blocker->name = name;
+	BUG_ON(!blocker->name);
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_blocker_init name=%s\n", blocker->name);
+
+	atomic_set(&blocker->flags, SB_INITIALIZED);
+}
+EXPORT_SYMBOL(suspend_blocker_init);
+
+/**
+ * suspend_blocker_destroy() - Destroy a suspend blocker
+ * @blocker:	The suspend blocker to destroy.
+ */
+void suspend_blocker_destroy(struct suspend_blocker *blocker)
+{
+	int flags;
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
+	flags = atomic_xchg(&blocker->flags, 0);
+	WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
+					"uninitialized suspend_blocker\n");
+	if (flags == (SB_INITIALIZED | SB_ACTIVE))
+		if (atomic_dec_and_test(&suspend_block_count))
+			queue_work(suspend_work_queue, &suspend_work);
+}
+EXPORT_SYMBOL(suspend_blocker_destroy);
+
+/**
+ * suspend_block() - Block suspend
+ * @blocker:	The suspend blocker to use
+ */
+void suspend_block(struct suspend_blocker *blocker)
+{
+	BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_block: %s\n", blocker->name);
+	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
+	    SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
+		atomic_inc(&suspend_block_count);
+
+	atomic_inc(&current_event_num);
+}
+EXPORT_SYMBOL(suspend_block);
+
+/**
+ * suspend_unblock() - Unblock suspend
+ * @blocker:	The suspend blocker to unblock.
+ *
+ * If no other suspend blockers block suspend, the system will suspend.
+ */
+void suspend_unblock(struct suspend_blocker *blocker)
+{
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_unblock: %s\n", blocker->name);
+
+	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
+	    SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
+		if (atomic_dec_and_test(&suspend_block_count))
+			queue_work(suspend_work_queue, &suspend_work);
+}
+EXPORT_SYMBOL(suspend_unblock);
+
+/**
+ * is_blocking_suspend() - Test if a suspend blocker is blocking suspend
+ * @blocker:	The suspend blocker to check.
+ */
+bool is_blocking_suspend(struct suspend_blocker *blocker)
+{
+	return !!(atomic_read(&blocker->flags) & SB_ACTIVE);
+}
+EXPORT_SYMBOL(is_blocking_suspend);
+
+void request_suspend_state(suspend_state_t state)
+{
+	unsigned long irqflags;
+	spin_lock_irqsave(&state_lock, irqflags);
+	if (debug_mask & DEBUG_USER_STATE) {
+		struct timespec ts;
+		struct rtc_time tm;
+		getnstimeofday(&ts);
+		rtc_time_to_tm(ts.tv_sec, &tm);
+		pr_info("request_suspend_state: %s (%d->%d) at %lld "
+			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
+			state != PM_SUSPEND_ON ? "sleep" : "wakeup",
+			requested_suspend_state, state,
+			ktime_to_ns(ktime_get()),
+			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
+	}
+	requested_suspend_state = state;
+	if (state == PM_SUSPEND_ON)
+		suspend_block(&main_suspend_blocker);
+	else
+		suspend_unblock(&main_suspend_blocker);
+	spin_unlock_irqrestore(&state_lock, irqflags);
+}
+
+static int __init suspend_block_init(void)
+{
+	int ret;
+
+	suspend_blocker_init(&main_suspend_blocker, "main");
+	suspend_block(&main_suspend_blocker);
+
+	ret = sysdev_class_register(&suspend_block_sysclass);
+	if (ret) {
+		pr_err("suspend_block_init: sysdev_class_register failed\n");
+		goto err_sysdev_class_register;
+	}
+	ret = sysdev_register(&suspend_block_sysdev);
+	if (ret) {
+		pr_err("suspend_block_init: suspend_block_sysdev failed\n");
+		goto err_sysdev_register;
+	}
+
+	suspend_work_queue = create_singlethread_workqueue("suspend");
+	if (suspend_work_queue == NULL) {
+		ret = -ENOMEM;
+		goto err_suspend_work_queue;
+	}
+
+	return 0;
+
+err_suspend_work_queue:
+	sysdev_unregister(&suspend_block_sysdev);
+err_sysdev_register:
+	sysdev_class_unregister(&suspend_block_sysclass);
+err_sysdev_class_register:
+	suspend_blocker_destroy(&main_suspend_blocker);
+	return ret;
+}
+
+static void  __exit suspend_block_exit(void)
+{
+	destroy_workqueue(suspend_work_queue);
+	sysdev_unregister(&suspend_block_sysdev);
+	sysdev_class_unregister(&suspend_block_sysclass);
+	suspend_blocker_destroy(&main_suspend_blocker);
+}
+
+core_initcall(suspend_block_init);
+module_exit(suspend_block_exit);
-- 
1.6.1

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[PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Arve Hjønnevåg]

Adds ioctls to create a suspend_blocker, and to block and unblock suspend.
To delete the suspend_blocker, close the device.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/suspend-blockers.txt |   17 ++++
 include/linux/suspend_block_dev.h        |   25 ++++++
 kernel/power/Kconfig                     |    9 ++
 kernel/power/Makefile                    |    1 +
 kernel/power/user_suspend_block.c        |  125 ++++++++++++++++++++++++++++++
 5 files changed, 177 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/suspend_block_dev.h
 create mode 100644 kernel/power/user_suspend_block.c

diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
index 743b870..35bc713 100644
--- a/Documentation/power/suspend-blockers.txt
+++ b/Documentation/power/suspend-blockers.txt
@@ -74,3 +74,20 @@ if (list_empty(&state->pending_work))
 else
 	suspend_block(&state->suspend_blocker);
 
+User-space API
+==============
+
+To create a suspend_blocker from user-space, open the suspend_blocker device:
+    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
+then call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_INIT(strlen(name)), name);
+
+To activate a suspend_blocker call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
+
+To unblock call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
+
+To destroy the suspend_blocker, close the device:
+    close(fd);
+
diff --git a/include/linux/suspend_block_dev.h b/include/linux/suspend_block_dev.h
new file mode 100644
index 0000000..a7c0bf9
--- /dev/null
+++ b/include/linux/suspend_block_dev.h
@@ -0,0 +1,25 @@
+/* include/linux/suspend_block_dev.h
+ *
+ * Copyright (C) 2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SUSPEND_BLOCK_DEV_H
+#define _LINUX_SUSPEND_BLOCK_DEV_H
+
+#include <linux/ioctl.h>
+
+#define SUSPEND_BLOCKER_IOCTL_INIT(len)		_IOC(_IOC_WRITE, 's', 0, len)
+#define SUSPEND_BLOCKER_IOCTL_BLOCK		_IO('s', 1)
+#define SUSPEND_BLOCKER_IOCTL_UNBLOCK		_IO('s', 3)
+
+#endif
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 9d1df13..2cf4c4d 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -126,6 +126,15 @@ config SUSPEND_BLOCK
 	  /sys/power/request_state, the requested sleep state will be entered
 	  when no suspend_blockers are active.
 
+config USER_SUSPEND_BLOCK
+	bool "Userspace suspend blockers"
+	depends on SUSPEND_BLOCK
+	default y
+	---help---
+	  User-space suspend block api. Creates a misc device with ioctls
+	  to create, block and unblock a suspend_blocker. The suspend_blocker
+	  will be deleted when the device is closed.
+
 config HIBERNATION
 	bool "Hibernation (aka 'suspend to disk')"
 	depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 29cdc9e..5c524f1 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_PM)		+= main.o
 obj-$(CONFIG_PM_SLEEP)		+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
 obj-$(CONFIG_SUSPEND_BLOCK)	+= suspend_block.o
+obj-$(CONFIG_USER_SUSPEND_BLOCK)	+= user_suspend_block.o
 obj-$(CONFIG_HIBERNATION)	+= swsusp.o disk.o snapshot.o swap.o user.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
diff --git a/kernel/power/user_suspend_block.c b/kernel/power/user_suspend_block.c
new file mode 100644
index 0000000..782407c
--- /dev/null
+++ b/kernel/power/user_suspend_block.c
@@ -0,0 +1,125 @@
+/* kernel/power/user_suspend_block.c
+ *
+ * Copyright (C) 2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/suspend_block.h>
+#include <linux/suspend_block_dev.h>
+
+enum {
+	DEBUG_FAILURE	= BIT(0),
+};
+static int debug_mask = DEBUG_FAILURE;
+module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
+
+static DEFINE_MUTEX(ioctl_lock);
+
+struct user_suspend_blocker {
+	struct suspend_blocker	blocker;
+	char			name[0];
+};
+
+static int create_user_suspend_blocker(struct file *file, void __user *name,
+				 size_t name_len)
+{
+	struct user_suspend_blocker *bl;
+	if (file->private_data)
+		return -EBUSY;
+	bl = kzalloc(sizeof(*bl) + name_len + 1, GFP_KERNEL);
+	if (!bl)
+		return -ENOMEM;
+	if (copy_from_user(bl->name, name, name_len))
+		goto err_fault;
+	suspend_blocker_init(&bl->blocker, bl->name);
+	file->private_data = bl;
+	return 0;
+
+err_fault:
+	kfree(bl);
+	return -EFAULT;
+}
+
+static long user_suspend_blocker_ioctl(struct file *file, unsigned int cmd,
+				unsigned long _arg)
+{
+	void __user *arg = (void __user *)_arg;
+	struct user_suspend_blocker *bl;
+	long ret;
+
+	mutex_lock(&ioctl_lock);
+	if ((cmd & ~IOCSIZE_MASK) == SUSPEND_BLOCKER_IOCTL_INIT(0)) {
+		ret = create_user_suspend_blocker(file, arg, _IOC_SIZE(cmd));
+		goto done;
+	}
+	bl = file->private_data;
+	if (!bl) {
+		ret = -ENOENT;
+		goto done;
+	}
+	switch (cmd) {
+	case SUSPEND_BLOCKER_IOCTL_BLOCK:
+		suspend_block(&bl->blocker);
+		ret = 0;
+		break;
+	case SUSPEND_BLOCKER_IOCTL_UNBLOCK:
+		suspend_unblock(&bl->blocker);
+		ret = 0;
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+done:
+	if (ret && debug_mask & DEBUG_FAILURE)
+		pr_err("user_suspend_blocker_ioctl: cmd %x failed, %ld\n",
+			cmd, ret);
+	mutex_unlock(&ioctl_lock);
+	return ret;
+}
+
+static int user_suspend_blocker_release(struct inode *inode, struct file *file)
+{
+	struct user_suspend_blocker *bl = file->private_data;
+	if (!bl)
+		return 0;
+	suspend_blocker_destroy(&bl->blocker);
+	kfree(bl);
+	return 0;
+}
+
+const struct file_operations user_suspend_blocker_fops = {
+	.release = user_suspend_blocker_release,
+	.unlocked_ioctl = user_suspend_blocker_ioctl,
+};
+
+struct miscdevice user_suspend_blocker_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "suspend_blocker",
+	.fops = &user_suspend_blocker_fops,
+};
+
+static int __init user_suspend_blocker_init(void)
+{
+	return misc_register(&user_suspend_blocker_device);
+}
+
+static void __exit user_suspend_blocker_exit(void)
+{
+	misc_deregister(&user_suspend_blocker_device);
+}
+
+module_init(user_suspend_blocker_init);
+module_exit(user_suspend_blocker_exit);
-- 
1.6.1

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[PATCH 3/8] PM: suspend_block: Abort task freezing if a suspend_blocker is active.

[Arve Hjønnevåg]

If a suspend_blocker is active, suspend will fail anyway. Since
try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
as soon as someone blocks suspend (e.g. from an interrupt handler) improves
the worst case wakeup latency.

On an older kernel where task freezing could fail for processes attached
to a debugger, this fixed a problem where the device sometimes hung for
20 seconds before the screen turned on.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 kernel/power/process.c |   23 ++++++++++++++++++-----
 1 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index ca63401..76d7cdb 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/syscalls.h>
 #include <linux/freezer.h>
+#include <linux/suspend_block.h>
 
 /* 
  * Timeout for stopping processes
@@ -36,6 +37,7 @@ static int try_to_freeze_tasks(bool sig_only)
 	struct timeval start, end;
 	u64 elapsed_csecs64;
 	unsigned int elapsed_csecs;
+	unsigned int wakeup = 0;
 
 	do_gettimeofday(&start);
 
@@ -62,6 +64,10 @@ static int try_to_freeze_tasks(bool sig_only)
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);
 		yield();			/* Yield is okay here */
+		if (todo && suspend_is_blocked()) {
+			wakeup = 1;
+			break;
+		}
 		if (time_after(jiffies, end_time))
 			break;
 	} while (todo);
@@ -77,11 +83,18 @@ static int try_to_freeze_tasks(bool sig_only)
 		 * and caller must call thaw_processes() if something fails),
 		 * but it cleans up leftover PF_FREEZE requests.
 		 */
-		printk("\n");
-		printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
-				"(%d tasks refusing to freeze):\n",
-				elapsed_csecs / 100, elapsed_csecs % 100, todo);
-		show_state();
+		if (wakeup) {
+			printk("\n");
+			printk(KERN_ERR "Freezing of %s aborted\n",
+					sig_only ? "user space " : "tasks ");
+		} else {
+			printk("\n");
+			printk(KERN_ERR
+			       "Freezing of tasks failed after %d.%02d seconds "
+			       "(%d tasks refusing to freeze):\n",
+			       elapsed_csecs / 100, elapsed_csecs % 100, todo);
+			show_state();
+		}
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
 			task_lock(p);
-- 
1.6.1

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[PATCH 4/8] Input: Block suspend while event queue is not empty.

[Arve Hjønnevåg]

Add an ioctl, EVIOCSSUSPENDBLOCK, to enables a suspend_blocker that will block
suspend while the event queue is not empty. This allows userspace code to
process input events while the device appears to be asleep.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 drivers/input/evdev.c |   21 +++++++++++++++++++++
 include/linux/input.h |    3 +++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index ed8baa0..3a61425 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -19,6 +19,7 @@
 #include <linux/input.h>
 #include <linux/major.h>
 #include <linux/device.h>
+#include <linux/suspend_block.h>
 #include "input-compat.h"
 
 struct evdev {
@@ -43,6 +44,8 @@ struct evdev_client {
 	struct fasync_struct *fasync;
 	struct evdev *evdev;
 	struct list_head node;
+	int use_suspend_blocker;
+	struct suspend_blocker suspend_blocker;
 };
 
 static struct evdev *evdev_table[EVDEV_MINORS];
@@ -55,6 +58,8 @@ static void evdev_pass_event(struct evdev_client *client,
 	 * Interrupts are disabled, just acquire the lock
 	 */
 	spin_lock(&client->buffer_lock);
+	if (client->use_suspend_blocker)
+		suspend_block(&client->suspend_blocker);
 	client->buffer[client->head++] = *event;
 	client->head &= EVDEV_BUFFER_SIZE - 1;
 	spin_unlock(&client->buffer_lock);
@@ -236,6 +241,8 @@ static int evdev_release(struct inode *inode, struct file *file)
 	mutex_unlock(&evdev->mutex);
 
 	evdev_detach_client(evdev, client);
+	if (client->use_suspend_blocker)
+		suspend_blocker_destroy(&client->suspend_blocker);
 	kfree(client);
 
 	evdev_close_device(evdev);
@@ -335,6 +342,8 @@ static int evdev_fetch_next_event(struct evdev_client *client,
 	if (have_event) {
 		*event = client->buffer[client->tail++];
 		client->tail &= EVDEV_BUFFER_SIZE - 1;
+		if (client->use_suspend_blocker && client->head == client->tail)
+			suspend_unblock(&client->suspend_blocker);
 	}
 
 	spin_unlock_irq(&client->buffer_lock);
@@ -585,6 +594,18 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
 		else
 			return evdev_ungrab(evdev, client);
 
+	case EVIOCGSUSPENDBLOCK:
+		return put_user(EV_VERSION, ip);
+
+	case EVIOCSSUSPENDBLOCK:
+		spin_lock_irq(&client->buffer_lock);
+		if ((client->use_suspend_blocker = !!p))
+			suspend_blocker_init(&client->suspend_blocker, "evdev");
+		else
+			suspend_blocker_destroy(&client->suspend_blocker);
+		spin_unlock_irq(&client->buffer_lock);
+		return 0;
+
 	default:
 
 		if (_IOC_TYPE(cmd) != 'E')
diff --git a/include/linux/input.h b/include/linux/input.h
index 1249a0c..67e2332 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -81,6 +81,9 @@ struct input_absinfo {
 
 #define EVIOCGRAB		_IOW('E', 0x90, int)			/* Grab/Release device */
 
+#define EVIOCGSUSPENDBLOCK	_IOR('E', 0x91, int)			/* get suspend block enable */
+#define EVIOCSSUSPENDBLOCK	_IOW('E', 0x91, int)			/* set suspend block enable */
+
 /*
  * Event types
  */
-- 
1.6.1

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[PATCH 5/8] PM: suspend_block: Switch to list of active and inactive suspend blockers

[Arve Hjønnevåg]

This allows active suspend blockers to be listed

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 include/linux/suspend_block.h |    5 ++-
 kernel/power/suspend_block.c  |   77 ++++++++++++++++++++++++++++------------
 2 files changed, 58 insertions(+), 24 deletions(-)

diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
index 7820c60..73ac5f7 100755
--- a/include/linux/suspend_block.h
+++ b/include/linux/suspend_block.h
@@ -16,12 +16,15 @@
 #ifndef _LINUX_SUSPEND_BLOCK_H
 #define _LINUX_SUSPEND_BLOCK_H
 
+#include <linux/list.h>
+
 /* A suspend_blocker prevents the system from entering suspend when active.
  */
 
 struct suspend_blocker {
 #ifdef CONFIG_SUSPEND_BLOCK
-	atomic_t            flags;
+	struct list_head    link;
+	int                 flags;
 	const char         *name;
 #endif
 };
diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
index b4f2191..697f52a 100644
--- a/kernel/power/suspend_block.c
+++ b/kernel/power/suspend_block.c
@@ -33,19 +33,29 @@ module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
 #define SB_INITIALIZED            (1U << 8)
 #define SB_ACTIVE                 (1U << 9)
 
+static DEFINE_SPINLOCK(list_lock);
 static DEFINE_SPINLOCK(state_lock);
-static atomic_t suspend_block_count;
-static atomic_t current_event_num;
+static LIST_HEAD(inactive_blockers);
+static LIST_HEAD(active_blockers);
+static int current_event_num;
 struct workqueue_struct *suspend_work_queue;
 struct suspend_blocker main_suspend_blocker;
 static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
 static bool enable_suspend_blockers;
 
+static void print_active_blockers_locked(void)
+{
+	struct suspend_blocker *blocker;
+
+	list_for_each_entry(blocker, &active_blockers, link)
+		pr_info("active suspend blocker %s\n", blocker->name);
+}
+
 bool suspend_is_blocked(void)
 {
 	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
 		return 0;
-	return !!atomic_read(&suspend_block_count);
+	return !list_empty(&active_blockers);
 }
 
 static void suspend_worker(struct work_struct *work)
@@ -62,7 +72,7 @@ retry:
 		goto abort;
 	}
 
-	entry_event_num = atomic_read(&current_event_num);
+	entry_event_num = current_event_num;
 	if (debug_mask & DEBUG_SUSPEND)
 		pr_info("suspend: enter suspend\n");
 	ret = pm_suspend(requested_suspend_state);
@@ -76,7 +86,7 @@ retry:
 			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
 			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
 	}
-	if (atomic_read(&current_event_num) == entry_event_num) {
+	if (current_event_num == entry_event_num) {
 		if (debug_mask & DEBUG_SUSPEND)
 			pr_info("suspend: pm_suspend returned with no event\n");
 		goto retry;
@@ -110,6 +120,8 @@ static struct sys_device suspend_block_sysdev = {
  */
 void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
 {
+	unsigned long irqflags = 0;
+
 	if (name)
 		blocker->name = name;
 	BUG_ON(!blocker->name);
@@ -117,7 +129,12 @@ void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_blocker_init name=%s\n", blocker->name);
 
-	atomic_set(&blocker->flags, SB_INITIALIZED);
+	blocker->flags = SB_INITIALIZED;
+	INIT_LIST_HEAD(&blocker->link);
+
+	spin_lock_irqsave(&list_lock, irqflags);
+	list_add(&blocker->link, &inactive_blockers);
+	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_blocker_init);
 
@@ -127,15 +144,15 @@ EXPORT_SYMBOL(suspend_blocker_init);
  */
 void suspend_blocker_destroy(struct suspend_blocker *blocker)
 {
-	int flags;
+	unsigned long irqflags;
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
-	flags = atomic_xchg(&blocker->flags, 0);
-	WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
-					"uninitialized suspend_blocker\n");
-	if (flags == (SB_INITIALIZED | SB_ACTIVE))
-		if (atomic_dec_and_test(&suspend_block_count))
-			queue_work(suspend_work_queue, &suspend_work);
+	spin_lock_irqsave(&list_lock, irqflags);
+	blocker->flags &= ~SB_INITIALIZED;
+	list_del(&blocker->link);
+	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
+		queue_work(suspend_work_queue, &suspend_work);
+	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_blocker_destroy);
 
@@ -145,15 +162,19 @@ EXPORT_SYMBOL(suspend_blocker_destroy);
  */
 void suspend_block(struct suspend_blocker *blocker)
 {
-	BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&list_lock, irqflags);
+	BUG_ON(!(blocker->flags & SB_INITIALIZED));
 
+	blocker->flags |= SB_ACTIVE;
+	list_del(&blocker->link);
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_block: %s\n", blocker->name);
-	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
-	    SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
-		atomic_inc(&suspend_block_count);
+	list_add(&blocker->link, &active_blockers);
 
-	atomic_inc(&current_event_num);
+	current_event_num++;
+	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_block);
 
@@ -165,13 +186,23 @@ EXPORT_SYMBOL(suspend_block);
  */
 void suspend_unblock(struct suspend_blocker *blocker)
 {
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&list_lock, irqflags);
+
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_unblock: %s\n", blocker->name);
+	list_del(&blocker->link);
+	list_add(&blocker->link, &inactive_blockers);
 
-	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
-	    SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
-		if (atomic_dec_and_test(&suspend_block_count))
-			queue_work(suspend_work_queue, &suspend_work);
+	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
+		queue_work(suspend_work_queue, &suspend_work);
+	blocker->flags &= ~(SB_ACTIVE);
+	if (blocker == &main_suspend_blocker) {
+		if (debug_mask & DEBUG_SUSPEND)
+			print_active_blockers_locked();
+	}
+	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_unblock);
 
@@ -181,7 +212,7 @@ EXPORT_SYMBOL(suspend_unblock);
  */
 bool is_blocking_suspend(struct suspend_blocker *blocker)
 {
-	return !!(atomic_read(&blocker->flags) & SB_ACTIVE);
+	return !!(blocker->flags & SB_ACTIVE);
 }
 EXPORT_SYMBOL(is_blocking_suspend);
 
-- 
1.6.1

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[PATCH 6/8] PM: suspend_block: Add suspend_blocker stats

[Arve Hjønnevåg]

Report suspend block stats in /proc/suspend_blockers.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 include/linux/suspend_block.h |   11 +++
 kernel/power/Kconfig          |    7 ++
 kernel/power/suspend_block.c  |  201 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 217 insertions(+), 2 deletions(-)

diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
index 73ac5f7..31225c5 100755
--- a/include/linux/suspend_block.h
+++ b/include/linux/suspend_block.h
@@ -17,6 +17,7 @@
 #define _LINUX_SUSPEND_BLOCK_H
 
 #include <linux/list.h>
+#include <linux/ktime.h>
 
 /* A suspend_blocker prevents the system from entering suspend when active.
  */
@@ -26,6 +27,16 @@ struct suspend_blocker {
 	struct list_head    link;
 	int                 flags;
 	const char         *name;
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	struct {
+		int             count;
+		int             wakeup_count;
+		ktime_t         total_time;
+		ktime_t         prevent_suspend_time;
+		ktime_t         max_time;
+		ktime_t         last_time;
+	} stat;
+#endif
 #endif
 };
 
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 2cf4c4d..3de0c5f 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -126,6 +126,13 @@ config SUSPEND_BLOCK
 	  /sys/power/request_state, the requested sleep state will be entered
 	  when no suspend_blockers are active.
 
+config SUSPEND_BLOCK_STAT
+	bool "Suspend block stats"
+	depends on SUSPEND_BLOCK
+	default y
+	---help---
+	  Report suspend block stats in /proc/suspend_blockers
+
 config USER_SUSPEND_BLOCK
 	bool "Userspace suspend blockers"
 	depends on SUSPEND_BLOCK
diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
index 697f52a..78d5880 100644
--- a/kernel/power/suspend_block.c
+++ b/kernel/power/suspend_block.c
@@ -18,6 +18,9 @@
 #include <linux/suspend.h>
 #include <linux/suspend_block.h>
 #include <linux/sysdev.h>
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+#include <linux/proc_fs.h>
+#endif
 #include "power.h"
 
 enum {
@@ -32,6 +35,7 @@ module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
 
 #define SB_INITIALIZED            (1U << 8)
 #define SB_ACTIVE                 (1U << 9)
+#define SB_PREVENTING_SUSPEND     (1U << 10)
 
 static DEFINE_SPINLOCK(list_lock);
 static DEFINE_SPINLOCK(state_lock);
@@ -42,6 +46,165 @@ struct workqueue_struct *suspend_work_queue;
 struct suspend_blocker main_suspend_blocker;
 static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
 static bool enable_suspend_blockers;
+static struct suspend_blocker unknown_wakeup;
+
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+static struct suspend_blocker deleted_suspend_blockers;
+static ktime_t last_sleep_time_update;
+static bool wait_for_wakeup;
+
+static int print_blocker_stat(char *buf, struct suspend_blocker *blocker)
+{
+	int lock_count = blocker->stat.count;
+	ktime_t active_time = ktime_set(0, 0);
+	ktime_t total_time = blocker->stat.total_time;
+	ktime_t max_time = blocker->stat.max_time;
+	ktime_t prevent_suspend_time = blocker->stat.prevent_suspend_time;
+	if (blocker->flags & SB_ACTIVE) {
+		ktime_t now, add_time;
+		now = ktime_get();
+		add_time = ktime_sub(now, blocker->stat.last_time);
+		lock_count++;
+		active_time = add_time;
+		total_time = ktime_add(total_time, add_time);
+		if (blocker->flags & SB_PREVENTING_SUSPEND)
+			prevent_suspend_time = ktime_add(prevent_suspend_time,
+					ktime_sub(now, last_sleep_time_update));
+		if (add_time.tv64 > max_time.tv64)
+			max_time = add_time;
+	}
+
+	return sprintf(buf, "\"%s\"\t%d\t%d\t%lld\t%lld\t%lld\t%lld\t%lld\n",
+		       blocker->name, lock_count, blocker->stat.wakeup_count,
+		       ktime_to_ns(active_time), ktime_to_ns(total_time),
+		       ktime_to_ns(prevent_suspend_time), ktime_to_ns(max_time),
+		       ktime_to_ns(blocker->stat.last_time));
+}
+
+
+static int suspend_blocker_stats_read_proc(char *page, char **start, off_t off,
+			       int count, int *eof, void *data)
+{
+	unsigned long irqflags;
+	struct suspend_blocker *blocker;
+	int len = 0;
+	char *p = page;
+
+	spin_lock_irqsave(&list_lock, irqflags);
+
+	p += sprintf(p, "name\tcount\twake_count\tactive_since"
+		     "\ttotal_time\tsleep_time\tmax_time\tlast_change\n");
+	list_for_each_entry(blocker, &inactive_blockers, link) {
+		p += print_blocker_stat(p, blocker);
+	}
+	list_for_each_entry(blocker, &active_blockers, link)
+		p += print_blocker_stat(p, blocker);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+
+	*start = page + off;
+
+	len = p - page;
+	if (len > off)
+		len -= off;
+	else
+		len = 0;
+
+	return len < count ? len  : count;
+}
+
+static void suspend_blocker_stat_init_locked(struct suspend_blocker *blocker)
+{
+	blocker->stat.count = 0;
+	blocker->stat.wakeup_count = 0;
+	blocker->stat.total_time = ktime_set(0, 0);
+	blocker->stat.prevent_suspend_time = ktime_set(0, 0);
+	blocker->stat.max_time = ktime_set(0, 0);
+	blocker->stat.last_time = ktime_set(0, 0);
+}
+
+static void suspend_blocker_stat_destroy_locked(struct suspend_blocker *bl)
+{
+	if (!bl->stat.count)
+		return;
+	deleted_suspend_blockers.stat.count += bl->stat.count;
+	deleted_suspend_blockers.stat.total_time = ktime_add(
+		deleted_suspend_blockers.stat.total_time, bl->stat.total_time);
+	deleted_suspend_blockers.stat.prevent_suspend_time = ktime_add(
+		deleted_suspend_blockers.stat.prevent_suspend_time,
+		bl->stat.prevent_suspend_time);
+	deleted_suspend_blockers.stat.max_time = ktime_add(
+		deleted_suspend_blockers.stat.max_time, bl->stat.max_time);
+}
+
+static void suspend_unblock_stat_locked(struct suspend_blocker *blocker)
+{
+	ktime_t duration;
+	ktime_t now;
+	if (!(blocker->flags & SB_ACTIVE))
+		return;
+	now = ktime_get();
+	blocker->stat.count++;
+	duration = ktime_sub(now, blocker->stat.last_time);
+	blocker->stat.total_time =
+		ktime_add(blocker->stat.total_time, duration);
+	if (ktime_to_ns(duration) > ktime_to_ns(blocker->stat.max_time))
+		blocker->stat.max_time = duration;
+	blocker->stat.last_time = ktime_get();
+	if (blocker->flags & SB_PREVENTING_SUSPEND) {
+		duration = ktime_sub(now, last_sleep_time_update);
+		blocker->stat.prevent_suspend_time = ktime_add(
+			blocker->stat.prevent_suspend_time, duration);
+		blocker->flags &= ~SB_PREVENTING_SUSPEND;
+	}
+}
+
+static void suspend_block_stat_locked(struct suspend_blocker *blocker)
+{
+	if (wait_for_wakeup) {
+		if (debug_mask & DEBUG_WAKEUP)
+			pr_info("wakeup suspend blocker: %s\n", blocker->name);
+		wait_for_wakeup = false;
+		blocker->stat.wakeup_count++;
+	}
+	if (!(blocker->flags & SB_ACTIVE))
+		blocker->stat.last_time = ktime_get();
+}
+
+static void update_sleep_wait_stats_locked(bool done)
+{
+	struct suspend_blocker *blocker;
+	ktime_t now, elapsed, add;
+
+	now = ktime_get();
+	elapsed = ktime_sub(now, last_sleep_time_update);
+	list_for_each_entry(blocker, &active_blockers, link) {
+		if (blocker->flags & SB_PREVENTING_SUSPEND) {
+			add = elapsed;
+			blocker->stat.prevent_suspend_time = ktime_add(
+				blocker->stat.prevent_suspend_time, add);
+		}
+		if (done)
+			blocker->flags &= ~SB_PREVENTING_SUSPEND;
+		else
+			blocker->flags |= SB_PREVENTING_SUSPEND;
+	}
+	last_sleep_time_update = now;
+}
+
+#else
+
+static inline void suspend_blocker_stat_init_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_blocker_stat_destroy_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_block_stat_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_unblock_stat_locked(
+					struct suspend_blocker *blocker) {}
+static inline void update_sleep_wait_stats_locked(bool done) {}
+
+#endif
+
 
 static void print_active_blockers_locked(void)
 {
@@ -65,7 +228,6 @@ static void suspend_worker(struct work_struct *work)
 
 	enable_suspend_blockers = 1;
 
-retry:
 	if (suspend_is_blocked()) {
 		if (debug_mask & DEBUG_SUSPEND)
 			pr_info("suspend: abort suspend\n");
@@ -89,7 +251,8 @@ retry:
 	if (current_event_num == entry_event_num) {
 		if (debug_mask & DEBUG_SUSPEND)
 			pr_info("suspend: pm_suspend returned with no event\n");
-		goto retry;
+		suspend_block(&unknown_wakeup);
+		suspend_unblock(&unknown_wakeup);
 	}
 abort:
 	enable_suspend_blockers = 0;
@@ -99,6 +262,9 @@ static DECLARE_WORK(suspend_work, suspend_worker);
 static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
 {
 	int ret = suspend_is_blocked() ? -EAGAIN : 0;
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	wait_for_wakeup = true;
+#endif
 	if (debug_mask & DEBUG_SUSPEND)
 		pr_info("suspend_block_suspend return %d\n", ret);
 	return ret;
@@ -133,6 +299,7 @@ void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
 	INIT_LIST_HEAD(&blocker->link);
 
 	spin_lock_irqsave(&list_lock, irqflags);
+	suspend_blocker_stat_init_locked(blocker);
 	list_add(&blocker->link, &inactive_blockers);
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
@@ -148,6 +315,7 @@ void suspend_blocker_destroy(struct suspend_blocker *blocker)
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
 	spin_lock_irqsave(&list_lock, irqflags);
+	suspend_blocker_stat_destroy_locked(blocker);
 	blocker->flags &= ~SB_INITIALIZED;
 	list_del(&blocker->link);
 	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
@@ -167,6 +335,7 @@ void suspend_block(struct suspend_blocker *blocker)
 	spin_lock_irqsave(&list_lock, irqflags);
 	BUG_ON(!(blocker->flags & SB_INITIALIZED));
 
+	suspend_block_stat_locked(blocker);
 	blocker->flags |= SB_ACTIVE;
 	list_del(&blocker->link);
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
@@ -174,6 +343,10 @@ void suspend_block(struct suspend_blocker *blocker)
 	list_add(&blocker->link, &active_blockers);
 
 	current_event_num++;
+	if (blocker == &main_suspend_blocker)
+		update_sleep_wait_stats_locked(true);
+	else if (!is_blocking_suspend(&main_suspend_blocker))
+		update_sleep_wait_stats_locked(false);
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_block);
@@ -190,6 +363,8 @@ void suspend_unblock(struct suspend_blocker *blocker)
 
 	spin_lock_irqsave(&list_lock, irqflags);
 
+	suspend_unblock_stat_locked(blocker);
+
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_unblock: %s\n", blocker->name);
 	list_del(&blocker->link);
@@ -201,6 +376,7 @@ void suspend_unblock(struct suspend_blocker *blocker)
 	if (blocker == &main_suspend_blocker) {
 		if (debug_mask & DEBUG_SUSPEND)
 			print_active_blockers_locked();
+		update_sleep_wait_stats_locked(false);
 	}
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
@@ -245,8 +421,13 @@ static int __init suspend_block_init(void)
 {
 	int ret;
 
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	suspend_blocker_init(&deleted_suspend_blockers,
+				"deleted_suspend_blockers");
+#endif
 	suspend_blocker_init(&main_suspend_blocker, "main");
 	suspend_block(&main_suspend_blocker);
+	suspend_blocker_init(&unknown_wakeup, "unknown_wakeups");
 
 	ret = sysdev_class_register(&suspend_block_sysclass);
 	if (ret) {
@@ -265,6 +446,11 @@ static int __init suspend_block_init(void)
 		goto err_suspend_work_queue;
 	}
 
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	create_proc_read_entry("suspend_blockers", S_IRUGO, NULL,
+				suspend_blocker_stats_read_proc, NULL);
+#endif
+
 	return 0;
 
 err_suspend_work_queue:
@@ -272,16 +458,27 @@ err_suspend_work_queue:
 err_sysdev_register:
 	sysdev_class_unregister(&suspend_block_sysclass);
 err_sysdev_class_register:
+	suspend_blocker_destroy(&unknown_wakeup);
 	suspend_blocker_destroy(&main_suspend_blocker);
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	suspend_blocker_destroy(&deleted_suspend_blockers);
+#endif
 	return ret;
 }
 
 static void  __exit suspend_block_exit(void)
 {
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	remove_proc_entry("suspend_blockers", NULL);
+#endif
 	destroy_workqueue(suspend_work_queue);
 	sysdev_unregister(&suspend_block_sysdev);
 	sysdev_class_unregister(&suspend_block_sysclass);
+	suspend_blocker_destroy(&unknown_wakeup);
 	suspend_blocker_destroy(&main_suspend_blocker);
+#ifdef CONFIG_SUSPEND_BLOCK_STAT
+	suspend_blocker_destroy(&deleted_suspend_blockers);
+#endif
 }
 
 core_initcall(suspend_block_init);
-- 
1.6.1

_______________________________________________
linux-pm mailing list
linux-pm@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/linux-pm

[PATCH 7/8] PM: suspend_block: Add timeout support.

[Arve Hjønnevåg]

Add suspend_block_timeout to block suspend for a limited time.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/suspend-blockers.txt |   10 ++
 include/linux/suspend_block.h            |    7 +
 kernel/power/suspend_block.c             |  232 +++++++++++++++++++++++++-----
 3 files changed, 216 insertions(+), 33 deletions(-)

diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
index 35bc713..2781e05 100644
--- a/Documentation/power/suspend-blockers.txt
+++ b/Documentation/power/suspend-blockers.txt
@@ -74,6 +74,16 @@ if (list_empty(&state->pending_work))
 else
 	suspend_block(&state->suspend_blocker);
 
+A driver can also call suspend_block_timeout to release the suspend_blocker
+after a delay:
+	suspend_block_timeout(&state->suspend_blocker, HZ);
+
+This works whether the suspend_blocker is already active or not. It is useful if
+the driver woke up other parts of the system that do not use suspend_blockers
+but still need to run. Avoid this when possible, since it will waste power
+if the timeout is long or may fail to finish needed work if the timeout is
+short. Calling suspend_block or suspend_unblock will cancel the timeout.
+
 User-space API
 ==============
 
diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
index 31225c5..9cea772 100755
--- a/include/linux/suspend_block.h
+++ b/include/linux/suspend_block.h
@@ -27,9 +27,11 @@ struct suspend_blocker {
 	struct list_head    link;
 	int                 flags;
 	const char         *name;
+	unsigned long       expires;
 #ifdef CONFIG_SUSPEND_BLOCK_STAT
 	struct {
 		int             count;
+		int             expire_count;
 		int             wakeup_count;
 		ktime_t         total_time;
 		ktime_t         prevent_suspend_time;
@@ -45,9 +47,13 @@ struct suspend_blocker {
 void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
 void suspend_blocker_destroy(struct suspend_blocker *blocker);
 void suspend_block(struct suspend_blocker *blocker);
+void suspend_block_timeout(struct suspend_blocker *blocker, long timeout);
 void suspend_unblock(struct suspend_blocker *blocker);
 
 /* is_blocking_suspend returns true if the suspend_blocker is currently active.
+ * If the suspend_blocker has a timeout, it does not check the timeout, but if
+ * the timeout had already expired when it was checked elsewhere this function
+ * will return false.
  */
 bool is_blocking_suspend(struct suspend_blocker *blocker);
 
@@ -65,6 +71,7 @@ static inline void suspend_blocker_init(struct suspend_blocker *blocker,
 					const char *name) {}
 static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
 static inline void suspend_block(struct suspend_blocker *blocker) {}
+static inline void suspend_block_timeout(struct suspend_blocker *bl, long t) {}
 static inline void suspend_unblock(struct suspend_blocker *blocker) {}
 static inline bool is_blocking_suspend(struct suspend_blocker *bl) { return 0; }
 static inline bool suspend_is_blocked(void) { return 0; }
diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
index 78d5880..9414455 100644
--- a/kernel/power/suspend_block.c
+++ b/kernel/power/suspend_block.c
@@ -29,13 +29,15 @@ enum {
 	DEBUG_USER_STATE = 1U << 2,
 	DEBUG_SUSPEND = 1U << 3,
 	DEBUG_SUSPEND_BLOCKER = 1U << 4,
+	DEBUG_EXPIRE = 1U << 5,
 };
 static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
 module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
 
 #define SB_INITIALIZED            (1U << 8)
 #define SB_ACTIVE                 (1U << 9)
-#define SB_PREVENTING_SUSPEND     (1U << 10)
+#define SB_AUTO_EXPIRE            (1U << 10)
+#define SB_PREVENTING_SUSPEND     (1U << 11)
 
 static DEFINE_SPINLOCK(list_lock);
 static DEFINE_SPINLOCK(state_lock);
@@ -53,19 +55,53 @@ static struct suspend_blocker deleted_suspend_blockers;
 static ktime_t last_sleep_time_update;
 static bool wait_for_wakeup;
 
+static bool stats_get_expired_time(struct suspend_blocker *blocker,
+				   ktime_t *expire_time)
+{
+	struct timespec ts;
+	struct timespec kt;
+	struct timespec tomono;
+	struct timespec delta;
+	unsigned long seq;
+	long timeout;
+
+	if (!(blocker->flags & SB_AUTO_EXPIRE))
+		return false;
+	do {
+		seq = read_seqbegin(&xtime_lock);
+		timeout = blocker->expires - jiffies;
+		if (timeout > 0)
+			return false;
+		kt = current_kernel_time();
+		tomono = wall_to_monotonic;
+	} while (read_seqretry(&xtime_lock, seq));
+	jiffies_to_timespec(-timeout, &delta);
+	set_normalized_timespec(&ts, kt.tv_sec + tomono.tv_sec - delta.tv_sec,
+				kt.tv_nsec + tomono.tv_nsec - delta.tv_nsec);
+	*expire_time = timespec_to_ktime(ts);
+	return true;
+}
+
+
 static int print_blocker_stat(char *buf, struct suspend_blocker *blocker)
 {
 	int lock_count = blocker->stat.count;
+	int expire_count = blocker->stat.expire_count;
 	ktime_t active_time = ktime_set(0, 0);
 	ktime_t total_time = blocker->stat.total_time;
 	ktime_t max_time = blocker->stat.max_time;
 	ktime_t prevent_suspend_time = blocker->stat.prevent_suspend_time;
 	if (blocker->flags & SB_ACTIVE) {
 		ktime_t now, add_time;
-		now = ktime_get();
+		bool expired = stats_get_expired_time(blocker, &now);
+		if (!expired)
+			now = ktime_get();
 		add_time = ktime_sub(now, blocker->stat.last_time);
 		lock_count++;
-		active_time = add_time;
+		if (!expired)
+			active_time = add_time;
+		else
+			expire_count++;
 		total_time = ktime_add(total_time, add_time);
 		if (blocker->flags & SB_PREVENTING_SUSPEND)
 			prevent_suspend_time = ktime_add(prevent_suspend_time,
@@ -74,9 +110,10 @@ static int print_blocker_stat(char *buf, struct suspend_blocker *blocker)
 			max_time = add_time;
 	}
 
-	return sprintf(buf, "\"%s\"\t%d\t%d\t%lld\t%lld\t%lld\t%lld\t%lld\n",
-		       blocker->name, lock_count, blocker->stat.wakeup_count,
-		       ktime_to_ns(active_time), ktime_to_ns(total_time),
+	return sprintf(buf, "\"%s\"\t%d\t%d\t%d\t%lld\t%lld\t%lld\t%lld\t"
+		       "%lld\n", blocker->name, lock_count, expire_count,
+		       blocker->stat.wakeup_count, ktime_to_ns(active_time),
+		       ktime_to_ns(total_time),
 		       ktime_to_ns(prevent_suspend_time), ktime_to_ns(max_time),
 		       ktime_to_ns(blocker->stat.last_time));
 }
@@ -92,7 +129,7 @@ static int suspend_blocker_stats_read_proc(char *page, char **start, off_t off,
 
 	spin_lock_irqsave(&list_lock, irqflags);
 
-	p += sprintf(p, "name\tcount\twake_count\tactive_since"
+	p += sprintf(p, "name\tcount\texpire_count\twake_count\tactive_since"
 		     "\ttotal_time\tsleep_time\tmax_time\tlast_change\n");
 	list_for_each_entry(blocker, &inactive_blockers, link) {
 		p += print_blocker_stat(p, blocker);
@@ -115,6 +152,7 @@ static int suspend_blocker_stats_read_proc(char *page, char **start, off_t off,
 static void suspend_blocker_stat_init_locked(struct suspend_blocker *blocker)
 {
 	blocker->stat.count = 0;
+	blocker->stat.expire_count = 0;
 	blocker->stat.wakeup_count = 0;
 	blocker->stat.total_time = ktime_set(0, 0);
 	blocker->stat.prevent_suspend_time = ktime_set(0, 0);
@@ -127,6 +165,7 @@ static void suspend_blocker_stat_destroy_locked(struct suspend_blocker *bl)
 	if (!bl->stat.count)
 		return;
 	deleted_suspend_blockers.stat.count += bl->stat.count;
+	deleted_suspend_blockers.stat.expire_count += bl->stat.expire_count;
 	deleted_suspend_blockers.stat.total_time = ktime_add(
 		deleted_suspend_blockers.stat.total_time, bl->stat.total_time);
 	deleted_suspend_blockers.stat.prevent_suspend_time = ktime_add(
@@ -136,14 +175,20 @@ static void suspend_blocker_stat_destroy_locked(struct suspend_blocker *bl)
 		deleted_suspend_blockers.stat.max_time, bl->stat.max_time);
 }
 
-static void suspend_unblock_stat_locked(struct suspend_blocker *blocker)
+static void suspend_unblock_stat_locked(struct suspend_blocker *blocker,
+					bool expired)
 {
 	ktime_t duration;
 	ktime_t now;
 	if (!(blocker->flags & SB_ACTIVE))
 		return;
-	now = ktime_get();
+	if (stats_get_expired_time(blocker, &now))
+		expired = true;
+	else
+		now = ktime_get();
 	blocker->stat.count++;
+	if (expired)
+		blocker->stat.expire_count++;
 	duration = ktime_sub(now, blocker->stat.last_time);
 	blocker->stat.total_time =
 		ktime_add(blocker->stat.total_time, duration);
@@ -166,6 +211,12 @@ static void suspend_block_stat_locked(struct suspend_blocker *blocker)
 		wait_for_wakeup = false;
 		blocker->stat.wakeup_count++;
 	}
+	if ((blocker->flags & SB_AUTO_EXPIRE) &&
+	    time_is_before_eq_jiffies(blocker->expires)) {
+		suspend_unblock_stat_locked(blocker, false);
+		blocker->stat.last_time = ktime_get();
+	}
+
 	if (!(blocker->flags & SB_ACTIVE))
 		blocker->stat.last_time = ktime_get();
 }
@@ -173,17 +224,22 @@ static void suspend_block_stat_locked(struct suspend_blocker *blocker)
 static void update_sleep_wait_stats_locked(bool done)
 {
 	struct suspend_blocker *blocker;
-	ktime_t now, elapsed, add;
+	ktime_t now, etime, elapsed, add;
+	bool expired;
 
 	now = ktime_get();
 	elapsed = ktime_sub(now, last_sleep_time_update);
 	list_for_each_entry(blocker, &active_blockers, link) {
+		expired = stats_get_expired_time(blocker, &etime);
 		if (blocker->flags & SB_PREVENTING_SUSPEND) {
-			add = elapsed;
+			if (expired)
+				add = ktime_sub(etime, last_sleep_time_update);
+			else
+				add = elapsed;
 			blocker->stat.prevent_suspend_time = ktime_add(
 				blocker->stat.prevent_suspend_time, add);
 		}
-		if (done)
+		if (done || expired)
 			blocker->flags &= ~SB_PREVENTING_SUSPEND;
 		else
 			blocker->flags |= SB_PREVENTING_SUSPEND;
@@ -199,26 +255,69 @@ static inline void suspend_blocker_stat_destroy_locked(
 					struct suspend_blocker *blocker) {}
 static inline void suspend_block_stat_locked(
 					struct suspend_blocker *blocker) {}
-static inline void suspend_unblock_stat_locked(
-					struct suspend_blocker *blocker) {}
+static inline void suspend_unblock_stat_locked(struct suspend_blocker *blocker,
+					   bool expired) {}
 static inline void update_sleep_wait_stats_locked(bool done) {}
 
 #endif
 
 
+static void expire_suspend_blocker(struct suspend_blocker *blocker)
+{
+	suspend_unblock_stat_locked(blocker, true);
+	blocker->flags &= ~(SB_ACTIVE | SB_AUTO_EXPIRE);
+	list_del(&blocker->link);
+	list_add(&blocker->link, &inactive_blockers);
+	if (debug_mask & (DEBUG_SUSPEND_BLOCKER | DEBUG_EXPIRE))
+		pr_info("expired suspend blocker %s\n", blocker->name);
+}
+
 static void print_active_blockers_locked(void)
 {
 	struct suspend_blocker *blocker;
 
-	list_for_each_entry(blocker, &active_blockers, link)
-		pr_info("active suspend blocker %s\n", blocker->name);
+	list_for_each_entry(blocker, &active_blockers, link) {
+		if (blocker->flags & SB_AUTO_EXPIRE) {
+			long timeout = blocker->expires - jiffies;
+			if (timeout <= 0)
+				pr_info("suspend blocker %s, expired\n",
+					blocker->name);
+			else
+				pr_info("active suspend blocker %s, time left "
+					"%ld\n", blocker->name, timeout);
+		} else
+			pr_info("active suspend blocker %s\n", blocker->name);
+	}
+}
+
+static long max_suspend_blocker_timeout_locked(void)
+{
+	struct suspend_blocker *blocker, *n;
+	long max_timeout = 0;
+
+	list_for_each_entry_safe(blocker, n, &active_blockers, link) {
+		if (blocker->flags & SB_AUTO_EXPIRE) {
+			long timeout = blocker->expires - jiffies;
+			if (timeout <= 0)
+				expire_suspend_blocker(blocker);
+			else if (timeout > max_timeout)
+				max_timeout = timeout;
+		} else
+			return -1;
+	}
+	return max_timeout;
 }
 
 bool suspend_is_blocked(void)
 {
+	long ret;
+	unsigned long irqflags;
 	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
 		return 0;
-	return !list_empty(&active_blockers);
+	spin_lock_irqsave(&list_lock, irqflags);
+	ret = !!max_suspend_blocker_timeout_locked();
+	spin_unlock_irqrestore(&list_lock, irqflags);
+	return ret;
 }
 
 static void suspend_worker(struct work_struct *work)
@@ -251,14 +350,49 @@ static void suspend_worker(struct work_struct *work)
 	if (current_event_num == entry_event_num) {
 		if (debug_mask & DEBUG_SUSPEND)
 			pr_info("suspend: pm_suspend returned with no event\n");
-		suspend_block(&unknown_wakeup);
-		suspend_unblock(&unknown_wakeup);
+		suspend_block_timeout(&unknown_wakeup, HZ / 2);
 	}
 abort:
 	enable_suspend_blockers = 0;
 }
 static DECLARE_WORK(suspend_work, suspend_worker);
 
+static void expire_suspend_blockers(unsigned long data)
+{
+	long timeout;
+	unsigned long irqflags;
+	if (debug_mask & DEBUG_EXPIRE)
+		pr_info("expire_suspend_blockers: start\n");
+	spin_lock_irqsave(&list_lock, irqflags);
+	if (debug_mask & DEBUG_SUSPEND)
+		print_active_blockers_locked();
+	timeout = max_suspend_blocker_timeout_locked();
+	if (debug_mask & DEBUG_EXPIRE)
+		pr_info("expire_suspend_blockers: done, timeout %ld\n",
+			timeout);
+	if (timeout == 0)
+		queue_work(suspend_work_queue, &suspend_work);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+}
+static DEFINE_TIMER(expire_timer, expire_suspend_blockers, 0, 0);
+
+static void update_suspend(struct suspend_blocker *blocker, long max_timeout)
+{
+	if (max_timeout > 0) {
+		if (debug_mask & DEBUG_EXPIRE)
+			pr_info("suspend_blocker: %s, start expire timer, "
+				"%ld\n", blocker->name, max_timeout);
+		mod_timer(&expire_timer, jiffies + max_timeout);
+	} else {
+		if (del_timer(&expire_timer))
+			if (debug_mask & DEBUG_EXPIRE)
+				pr_info("suspend_blocker: %s, stop expire "
+					"timer\n", blocker->name);
+		if (max_timeout == 0)
+			queue_work(suspend_work_queue, &suspend_work);
+	}
+}
+
 static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
 {
 	int ret = suspend_is_blocked() ? -EAGAIN : 0;
@@ -318,17 +452,14 @@ void suspend_blocker_destroy(struct suspend_blocker *blocker)
 	suspend_blocker_stat_destroy_locked(blocker);
 	blocker->flags &= ~SB_INITIALIZED;
 	list_del(&blocker->link);
-	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
-		queue_work(suspend_work_queue, &suspend_work);
+	if (blocker->flags & SB_ACTIVE)
+		update_suspend(blocker, max_suspend_blocker_timeout_locked());
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_blocker_destroy);
 
-/**
- * suspend_block() - Block suspend
- * @blocker:	The suspend blocker to use
- */
-void suspend_block(struct suspend_blocker *blocker)
+static void __suspend_block(struct suspend_blocker *blocker, long timeout,
+			    bool has_timeout)
 {
 	unsigned long irqflags;
 
@@ -338,20 +469,56 @@ void suspend_block(struct suspend_blocker *blocker)
 	suspend_block_stat_locked(blocker);
 	blocker->flags |= SB_ACTIVE;
 	list_del(&blocker->link);
-	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
-		pr_info("suspend_block: %s\n", blocker->name);
-	list_add(&blocker->link, &active_blockers);
+	if (has_timeout) {
+		if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+			pr_info("suspend_block: %s, timeout %ld.%03lu\n",
+				blocker->name, timeout / HZ,
+				(timeout % HZ) * MSEC_PER_SEC / HZ);
+		blocker->expires = jiffies + timeout;
+		blocker->flags |= SB_AUTO_EXPIRE;
+		list_add_tail(&blocker->link, &active_blockers);
+	} else {
+		if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+			pr_info("suspend_block: %s\n", blocker->name);
+		blocker->expires = LONG_MAX;
+		blocker->flags &= ~SB_AUTO_EXPIRE;
+		/* Add to head so suspend_is_blocked only has to examine */
+		/* one entry */
+		list_add(&blocker->link, &active_blockers);
+	}
 
 	current_event_num++;
 	if (blocker == &main_suspend_blocker)
 		update_sleep_wait_stats_locked(true);
 	else if (!is_blocking_suspend(&main_suspend_blocker))
 		update_sleep_wait_stats_locked(false);
+	update_suspend(blocker, has_timeout ?
+			max_suspend_blocker_timeout_locked() : -1);
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
+
+/**
+ * suspend_block() - Block suspend
+ * @blocker:	The suspend blocker to use
+ */
+void suspend_block(struct suspend_blocker *blocker)
+{
+	__suspend_block(blocker, 0, false);
+}
 EXPORT_SYMBOL(suspend_block);
 
 /**
+ * suspend_block_timeout() - Block suspend for a limited time
+ * @blocker:	The suspend blocker to use.
+ * @timeout:	Timeout in jiffies before the suspend blocker auto-unblock
+ */
+void suspend_block_timeout(struct suspend_blocker *blocker, long timeout)
+{
+	__suspend_block(blocker, timeout, true);
+}
+EXPORT_SYMBOL(suspend_block_timeout);
+
+/**
  * suspend_unblock() - Unblock suspend
  * @blocker:	The suspend blocker to unblock.
  *
@@ -363,16 +530,15 @@ void suspend_unblock(struct suspend_blocker *blocker)
 
 	spin_lock_irqsave(&list_lock, irqflags);
 
-	suspend_unblock_stat_locked(blocker);
+	suspend_unblock_stat_locked(blocker, false);
 
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_unblock: %s\n", blocker->name);
+	blocker->flags &= ~(SB_ACTIVE | SB_AUTO_EXPIRE);
 	list_del(&blocker->link);
 	list_add(&blocker->link, &inactive_blockers);
 
-	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
-		queue_work(suspend_work_queue, &suspend_work);
-	blocker->flags &= ~(SB_ACTIVE);
+	update_suspend(blocker, max_suspend_blocker_timeout_locked());
 	if (blocker == &main_suspend_blocker) {
 		if (debug_mask & DEBUG_SUSPEND)
 			print_active_blockers_locked();
-- 
1.6.1

_______________________________________________
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linux-pm@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/linux-pm

[PATCH 8/8] PM: suspend_block: Add timeout support to user-space suspend_blockers

[Arve Hjønnevåg]

This also allows a grace period to be set where suspend is blocked for a while
if a user-space suspend_blocker is destroyed while it was active.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/suspend-blockers.txt |    7 +++++++
 include/linux/suspend_block_dev.h        |    1 +
 kernel/power/user_suspend_block.c        |   22 ++++++++++++++++++++++
 3 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
index 2781e05..890f057 100644
--- a/Documentation/power/suspend-blockers.txt
+++ b/Documentation/power/suspend-blockers.txt
@@ -94,6 +94,8 @@ then call:
 
 To activate a suspend_blocker call:
     ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
+or
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK_TIMEOUT, &timespec_timeout);
 
 To unblock call:
     ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
@@ -101,3 +103,8 @@ To unblock call:
 To destroy the suspend_blocker, close the device:
     close(fd);
 
+A module parameter, unclean_exit_grace_period, can be set to allow servers
+some time to restart if they crash with an active suspend_blocker. If the
+process dies or the device is closed while the suspend_blocker is active, a
+suspend_blocker will be held for the number of seconds specified.
+
diff --git a/include/linux/suspend_block_dev.h b/include/linux/suspend_block_dev.h
index a7c0bf9..cff4943 100644
--- a/include/linux/suspend_block_dev.h
+++ b/include/linux/suspend_block_dev.h
@@ -20,6 +20,7 @@
 
 #define SUSPEND_BLOCKER_IOCTL_INIT(len)		_IOC(_IOC_WRITE, 's', 0, len)
 #define SUSPEND_BLOCKER_IOCTL_BLOCK		_IO('s', 1)
+#define SUSPEND_BLOCKER_IOCTL_BLOCK_TIMEOUT	_IOW('s', 2, struct timespec)
 #define SUSPEND_BLOCKER_IOCTL_UNBLOCK		_IO('s', 3)
 
 #endif
diff --git a/kernel/power/user_suspend_block.c b/kernel/power/user_suspend_block.c
index 782407c..1ba07dd 100644
--- a/kernel/power/user_suspend_block.c
+++ b/kernel/power/user_suspend_block.c
@@ -26,7 +26,12 @@ enum {
 static int debug_mask = DEBUG_FAILURE;
 module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
 
+static int unclean_exit_grace_period;
+module_param_named(unclean_exit_grace_period, unclean_exit_grace_period, int,
+						S_IRUGO | S_IWUSR | S_IWGRP);
+
 static DEFINE_MUTEX(ioctl_lock);
+static struct suspend_blocker unclean_exit_suspend_blocker;
 
 struct user_suspend_blocker {
 	struct suspend_blocker	blocker;
@@ -58,6 +63,8 @@ static long user_suspend_blocker_ioctl(struct file *file, unsigned int cmd,
 {
 	void __user *arg = (void __user *)_arg;
 	struct user_suspend_blocker *bl;
+	struct timespec ts;
+	unsigned long timeout;
 	long ret;
 
 	mutex_lock(&ioctl_lock);
@@ -75,6 +82,15 @@ static long user_suspend_blocker_ioctl(struct file *file, unsigned int cmd,
 		suspend_block(&bl->blocker);
 		ret = 0;
 		break;
+	case SUSPEND_BLOCKER_IOCTL_BLOCK_TIMEOUT:
+		if (copy_from_user(&ts, arg, sizeof(ts))) {
+			ret = -EFAULT;
+			goto done;
+		}
+		timeout  = timespec_to_jiffies(&ts);
+		suspend_block_timeout(&bl->blocker, timeout);
+		ret = 0;
+		break;
 	case SUSPEND_BLOCKER_IOCTL_UNBLOCK:
 		suspend_unblock(&bl->blocker);
 		ret = 0;
@@ -95,6 +111,9 @@ static int user_suspend_blocker_release(struct inode *inode, struct file *file)
 	struct user_suspend_blocker *bl = file->private_data;
 	if (!bl)
 		return 0;
+	if (is_blocking_suspend(&bl->blocker) && unclean_exit_grace_period)
+		suspend_block_timeout(&unclean_exit_suspend_blocker,
+					unclean_exit_grace_period * HZ);
 	suspend_blocker_destroy(&bl->blocker);
 	kfree(bl);
 	return 0;
@@ -113,12 +132,15 @@ struct miscdevice user_suspend_blocker_device = {
 
 static int __init user_suspend_blocker_init(void)
 {
+	suspend_blocker_init(&unclean_exit_suspend_blocker,
+				"user-unclean-exit");
 	return misc_register(&user_suspend_blocker_device);
 }
 
 static void __exit user_suspend_blocker_exit(void)
 {
 	misc_deregister(&user_suspend_blocker_device);
+	suspend_blocker_destroy(&unclean_exit_suspend_blocker);
 }
 
 module_init(user_suspend_blocker_init);
-- 
1.6.1

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linux-pm@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/linux-pm

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Tue, 14 Apr 2009, [utf-8] Arve Hjønnevåg wrote:

> +Suspend blockers can be used to allow user-space to decide which keys should
> +wake the full system up and turn the screen on.

This sentence still grates on me.  For readers not familiar with the 
embedded/phone environment, it won't make any sense.  Furthermore the 
rest of the text below doesn't even mention the screen, which will 
cause readers to wonder why it is mentioned here.

>  Use set_irq_wake or a platform
> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
> +driver has resumed, the sequence of events can look like this:
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> +- The user-space input-event thread returns from read. It determines that the
> +  key should not wake up the full system, calls suspend_unblock on the
> +  process-input-events suspend_blocker and calls select or poll.
> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++

How about replacing that first sentence with something like this:

	In cell phones or other embedded systems where powering the
	screen is a significant drain on the battery, suspend blockers 
	can be used to allow user-space to decide whether a keystroke
	received while the system is suspended should cause the screen 
	to be turned back on or allow the system to go back into 
	suspend.

Then in the last section, say this:

      - The user-space input-event thread returns from read. If it 
	determines that the key should leave the screen off, it
	calls suspend_unblock on the process_input_events
	suspend_blocker and then calls select or poll.  The system
	will automatically suspend again, since now no suspend blockers
	are active.

Alan Stern

Re: [PATCH 1/8] PM: Add suspend block api.

[mark gross]

On Wed, Apr 15, 2009 at 11:29:01AM -0400, Alan Stern wrote:
> On Tue, 14 Apr 2009, [utf-8] Arve Hjønnevåg wrote:
> 
> > +Suspend blockers can be used to allow user-space to decide which keys should
> > +wake the full system up and turn the screen on.
> 
> This sentence still grates on me.  For readers not familiar with the 
> embedded/phone environment, it won't make any sense.  Furthermore the 
> rest of the text below doesn't even mention the screen, which will 
> cause readers to wonder why it is mentioned here.
> 
> >  Use set_irq_wake or a platform
> > +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
> > +driver has resumed, the sequence of events can look like this:
> > +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> > +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> > +- The keypad-scan code detects a key change and reports it to the input-event
> > +  driver.
> > +- The input-event driver sees the key change, enqueues an event, and calls
> > +  suspend_block on the input-event-queue suspend_blocker.
> > +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> > +  on the keypad-scan suspend_blocker.
> > +- The user-space input-event thread returns from select/poll, calls
> > +  suspend_block on the process-input-events suspend_blocker and then calls read
> > +  on the input-event device.
> > +- The input-event driver dequeues the key-event and, since the queue is now
> > +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> > +- The user-space input-event thread returns from read. It determines that the
> > +  key should not wake up the full system, calls suspend_unblock on the
> > +  process-input-events suspend_blocker and calls select or poll.
> > +
> > +                 Key pressed   Key released
> > +                     |             |
> > +keypad-scan          ++++++++++++++++++
> > +input-event-queue        +++          +++
> > +process-input-events       +++          +++
> 
> How about replacing that first sentence with something like this:
> 
> 	In cell phones or other embedded systems where powering the
> 	screen is a significant drain on the battery, suspend blockers 
> 	can be used to allow user-space to decide whether a keystroke
> 	received while the system is suspended should cause the screen 
> 	to be turned back on or allow the system to go back into 
> 	suspend.
> 
> Then in the last section, say this:
> 
>       - The user-space input-event thread returns from read. If it 
> 	determines that the key should leave the screen off, it
> 	calls suspend_unblock on the process_input_events
> 	suspend_blocker and then calls select or poll.  The system
> 	will automatically suspend again, since now no suspend blockers
> 	are active.

I'm still re-reviewing the design so I probably should keep my mouth
shut, but I only see code for constraining entry into suspend state (S3
if you will)  I didn't see code that would get called to block device
entry into higher power states just constraints on entire system entry
into sleep state.  (I apologize if I missed that code and will happily
eat my words if needed.)

more comments after I finish looking over the code.

--mgross

 

Re: [PATCH 1/8] PM: Add suspend block api.

[mark gross]

I'm sure you are sick of this question, but couldn't you do this same
functionality (constraining entry to Suspend) using existing
infrastructure.  You are clearly aggregating a block-count and triggering
on an zero aggregate value to enter Suspend.

I'm thinking you could do something like CPUIDLE to push the implicit
suspend call and use a new pmqos parameter to keep the system alive.
We'd have to look at the API to make sure it would work in interrupt
mode.

The only thing I got from the earlier threads asking why not PMQOS, was
some complaint about the strcmp the constraint aggregation does WRT
performance.  I don't think it would be too hard to address the perceived
performance issue (even if its yet to be proven as an issue anywhere)

FWIW there is some talk of re-factoring some of pmqos to sit on top of a
constraint framework (to generalize the code a little and support
constraining things that are not really measurable in terms of latencies
or throughputs)

anyway a few comments below.

On Tue, Apr 14, 2009 at 06:41:25PM -0700, Arve Hjønnevåg wrote:
> Adds /sys/power/request_state, a non-blocking interface that specifies
> which suspend state to enter when no suspend blockers are active. A
> special state, "on", stops the process by activating the "main" suspend
> blocker.
> 
> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ---
>  Documentation/power/suspend-blockers.txt |   76 +++++++++
>  include/linux/suspend_block.h            |   61 +++++++
>  kernel/power/Kconfig                     |   10 ++
>  kernel/power/Makefile                    |    1 +
>  kernel/power/main.c                      |   62 +++++++
>  kernel/power/power.h                     |    6 +
>  kernel/power/suspend_block.c             |  257 ++++++++++++++++++++++++++++++
>  7 files changed, 473 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/power/suspend-blockers.txt
>  create mode 100755 include/linux/suspend_block.h
>  create mode 100644 kernel/power/suspend_block.c
> 
> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
> new file mode 100644
> index 0000000..743b870
> --- /dev/null
> +++ b/Documentation/power/suspend-blockers.txt
> @@ -0,0 +1,76 @@
> +Suspend blockers
> +================
> +
> +A suspend_blocker prevents the system from entering suspend.

And trigger implicit entry into suspend when last blocker is released.

> +
> +If the suspend operation has already started when calling suspend_block on a
> +suspend_blocker, it will abort the suspend operation as long it has not already
> +reached the sysdev suspend stage. This means that calling suspend_block from an
> +interrupt handler or a freezeable thread always works, but if you call
> +block_suspend from a sysdev suspend handler you must also return an error from
> +that handler to abort suspend.
> +
> +Suspend blockers can be used to allow user-space to decide which keys should
> +wake the full system up and turn the screen on. 

Provided the user mode process controlling the screen power is in the calling
path of user-space input-event thread.

Basically it should be made clear that this is not a device PM
implementation.  Its a global system suspend constraint system, where
the count of blockers is aggregated in a static variable,
suspend_block_count, within suspend_block.c  with implicit suspend
called when block count gets to zero.

i.e. only useful in platform specific code for platforms that can do
~10ms suspends and resumes.
 
> Use set_irq_wake or a platform
> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
> +driver has resumed, the sequence of events can look like this:
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
count = 1
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
count = 2
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
count = 1
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
count = 2
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
count = 1
> +- The user-space input-event thread returns from read. It determines that the
> +  key should not wake up the full system, calls suspend_unblock on the
> +  process-input-events suspend_blocker and calls select or poll.
count = 0 + race between dropping into Suspend state and the execution
of the select or poll.  (should probably be ok)

> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++
> +
> +
> +Driver API
> +==========
> +
> +A driver can use the suspend block api by adding a suspend_blocker variable to
> +its state and calling suspend_blocker_init. For instance:
> +struct state {
> +	struct suspend_blocker suspend_blocker;
> +}
> +
> +init() {
> +	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
> +}
> +
> +Before freeing the memory, suspend_blocker_destroy must be called:
> +
> +uninit() {
> +	suspend_blocker_destroy(&state->suspend_blocker);
> +}
> +
> +When the driver determines that it needs to run (usually in an interrupt
> +handler) it calls suspend_block:
> +	suspend_block(&state->suspend_blocker);
> +
> +When it no longer needs to run it calls suspend_unblock:
> +	suspend_unblock(&state->suspend_blocker);
> +
> +Calling suspend_block when the suspend blocker is active or suspend_unblock when
> +it is not active has no effect. This allows drivers to update their state and
> +call suspend suspend_block or suspend_unblock based on the result.
> +For instance:
> +
> +if (list_empty(&state->pending_work))
> +	suspend_unblock(&state->suspend_blocker);
> +else
> +	suspend_block(&state->suspend_blocker);
> +
> diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
> new file mode 100755
> index 0000000..7820c60
> --- /dev/null
> +++ b/include/linux/suspend_block.h
> @@ -0,0 +1,61 @@
> +/* include/linux/suspend_block.h
> + *
> + * Copyright (C) 2007-2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef _LINUX_SUSPEND_BLOCK_H
> +#define _LINUX_SUSPEND_BLOCK_H
> +
> +/* A suspend_blocker prevents the system from entering suspend when active.
> + */
> +
> +struct suspend_blocker {
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	atomic_t            flags;
> +	const char         *name;
> +#endif
> +};
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
> +void suspend_block(struct suspend_blocker *blocker);
> +void suspend_unblock(struct suspend_blocker *blocker);
> +
> +/* is_blocking_suspend returns true if the suspend_blocker is currently active.
> + */
> +bool is_blocking_suspend(struct suspend_blocker *blocker);
> +
> +/* suspend_is_blocked can be used by generic power management code to abort
> + * suspend.
> + *
> + * To preserve backward compatibility suspend_is_blocked returns 0 unless it
> + * is called during suspend initiated from the suspend_block code.
> + */
> +bool suspend_is_blocked(void);
> +
> +#else
> +
> +static inline void suspend_blocker_init(struct suspend_blocker *blocker,
> +					const char *name) {}
> +static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
> +static inline void suspend_block(struct suspend_blocker *blocker) {}
> +static inline void suspend_unblock(struct suspend_blocker *blocker) {}
> +static inline bool is_blocking_suspend(struct suspend_blocker *bl) { return 0; }
> +static inline bool suspend_is_blocked(void) { return 0; }
> +
> +#endif
> +
> +#endif
> +
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 23bd4da..9d1df13 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -116,6 +116,16 @@ config SUSPEND_FREEZER
>  
>  	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
>  
> +config SUSPEND_BLOCK
> +	bool "Suspend block"
> +	depends on PM
> +	select RTC_LIB
> +	default n
> +	---help---
> +	  Enable suspend_block. When user space requests a sleep state through
> +	  /sys/power/request_state, the requested sleep state will be entered
> +	  when no suspend_blockers are active.
> +
>  config HIBERNATION
>  	bool "Hibernation (aka 'suspend to disk')"
>  	depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
> index 720ea4f..29cdc9e 100644
> --- a/kernel/power/Makefile
> +++ b/kernel/power/Makefile
> @@ -6,6 +6,7 @@ endif
>  obj-$(CONFIG_PM)		+= main.o
>  obj-$(CONFIG_PM_SLEEP)		+= console.o
>  obj-$(CONFIG_FREEZER)		+= process.o
> +obj-$(CONFIG_SUSPEND_BLOCK)	+= suspend_block.o
>  obj-$(CONFIG_HIBERNATION)	+= swsusp.o disk.o snapshot.o swap.o user.o
>  
>  obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index c9632f8..e4c6b20 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -22,6 +22,7 @@
>  #include <linux/freezer.h>
>  #include <linux/vmstat.h>
>  #include <linux/syscalls.h>
> +#include <linux/suspend_block.h>
>  
>  #include "power.h"
>  
> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>  
>  
>  static const char * const pm_states[PM_SUSPEND_MAX] = {
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	[PM_SUSPEND_ON]		= "on",
> +#endif
>  	[PM_SUSPEND_STANDBY]	= "standby",
>  	[PM_SUSPEND_MEM]	= "mem",
>  };
> @@ -540,6 +544,61 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  
>  power_attr(state);
>  
> +/**
> + *	request_state - control system power state.
> + *
> + *	This is similar to state, but it does not block until the system
> + *	resumes, and it will try to re-enter the state until another state is
> + *	requested. Suspend blockers are respected and the requested state will
> + *	only be entered when no suspend blockers are active.
> + *	Write "on" to cancel.
> + */
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +static ssize_t request_state_show(struct kobject *kobj,
> +				  struct kobj_attribute *attr, char *buf)
> +{
> +	char *s = buf;
> +	int i;
> +
> +	for (i = 0; i < PM_SUSPEND_MAX; i++) {
> +		if (pm_states[i] && (i == PM_SUSPEND_ON || valid_state(i)))
> +			s += sprintf(s, "%s ", pm_states[i]);
> +	}
> +	if (s != buf)
> +		/* convert the last space to a newline */
> +		*(s-1) = '\n';
> +	return (s - buf);
> +}
> +
> +static ssize_t request_state_store(struct kobject *kobj,
> +				   struct kobj_attribute *attr,
> +				   const char *buf, size_t n)
> +{
> +	suspend_state_t state = PM_SUSPEND_ON;
> +	const char * const *s;
> +	char *p;
> +	int len;
> +	int error = -EINVAL;
> +
> +	p = memchr(buf, '\n', n);
> +	len = p ? p - buf : n;
> +
> +	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
> +		if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
> +			break;
> +	}
> +	if (state < PM_SUSPEND_MAX && *s)
> +		if (state == PM_SUSPEND_ON || valid_state(state)) {
> +			error = 0;
> +			request_suspend_state(state);
> +		}
> +	return error ? error : n;
> +}
> +
> +power_attr(request_state);
> +#endif /* CONFIG_SUSPEND_BLOCK */
> +
>  #ifdef CONFIG_PM_TRACE
>  int pm_trace_enabled;
>  
> @@ -567,6 +626,9 @@ power_attr(pm_trace);
>  
>  static struct attribute * g[] = {
>  	&state_attr.attr,
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	&request_state_attr.attr,
> +#endif
>  #ifdef CONFIG_PM_TRACE
>  	&pm_trace_attr.attr,
>  #endif
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 46b5ec7..2414a74 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
>  {
>  }
>  #endif
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +/* kernel/power/suspend_block.c */
> +void request_suspend_state(suspend_state_t state);
> +#endif
> +
> diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
> new file mode 100644
> index 0000000..b4f2191
> --- /dev/null
> +++ b/kernel/power/suspend_block.c
> @@ -0,0 +1,257 @@
> +/* kernel/power/suspend_block.c
> + *
> + * Copyright (C) 2005-2008 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/rtc.h>
> +#include <linux/suspend.h>
> +#include <linux/suspend_block.h>
> +#include <linux/sysdev.h>
> +#include "power.h"
> +
> +enum {
> +	DEBUG_EXIT_SUSPEND = 1U << 0,
> +	DEBUG_WAKEUP = 1U << 1,
> +	DEBUG_USER_STATE = 1U << 2,
> +	DEBUG_SUSPEND = 1U << 3,
> +	DEBUG_SUSPEND_BLOCKER = 1U << 4,
> +};
> +static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +#define SB_INITIALIZED            (1U << 8)
> +#define SB_ACTIVE                 (1U << 9)
> +
> +static DEFINE_SPINLOCK(state_lock);
> +static atomic_t suspend_block_count;

So if suspend_block_count is the lynch pin of the design, why have all
the suspend_blocker structs?  Why have all the logic around the
different suspend blocker instances?

It seems like a lot of extra effort for an atomic "stay awake" counter.


--mgross


> +static atomic_t current_event_num;
> +struct workqueue_struct *suspend_work_queue;
> +struct suspend_blocker main_suspend_blocker;
> +static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
> +static bool enable_suspend_blockers;
> +
> +bool suspend_is_blocked(void)
> +{
> +	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
> +		return 0;
> +	return !!atomic_read(&suspend_block_count);
> +}
> +
> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = 1;
> +
> +retry:
> +	if (suspend_is_blocked()) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: abort suspend\n");
> +		goto abort;
> +	}
> +
> +	entry_event_num = atomic_read(&current_event_num);
> +	if (debug_mask & DEBUG_SUSPEND)
> +		pr_info("suspend: enter suspend\n");
> +	ret = pm_suspend(requested_suspend_state);
> +	if (debug_mask & DEBUG_EXIT_SUSPEND) {
> +		struct timespec ts;
> +		struct rtc_time tm;
> +		getnstimeofday(&ts);
> +		rtc_time_to_tm(ts.tv_sec, &tm);
> +		pr_info("suspend: exit suspend, ret = %d "
> +			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
> +	}
> +	if (atomic_read(&current_event_num) == entry_event_num) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: pm_suspend returned with no event\n");
> +		goto retry;
> +	}
> +abort:
> +	enable_suspend_blockers = 0;
> +}
> +static DECLARE_WORK(suspend_work, suspend_worker);
> +
> +static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
> +{
> +	int ret = suspend_is_blocked() ? -EAGAIN : 0;
> +	if (debug_mask & DEBUG_SUSPEND)
> +		pr_info("suspend_block_suspend return %d\n", ret);
> +	return ret;
> +}
> +
> +static struct sysdev_class suspend_block_sysclass = {
> +	.name = "suspend_block",
> +	.suspend = suspend_block_suspend,
> +};
> +static struct sys_device suspend_block_sysdev = {
> +	.cls = &suspend_block_sysclass,
> +};
> +
> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in
> + *		/proc/suspend_blockers
> + */
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
> +{
> +	if (name)
> +		blocker->name = name;
> +	BUG_ON(!blocker->name);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_init name=%s\n", blocker->name);
> +
> +	atomic_set(&blocker->flags, SB_INITIALIZED);
> +}
> +EXPORT_SYMBOL(suspend_blocker_init);
> +
> +/**
> + * suspend_blocker_destroy() - Destroy a suspend blocker
> + * @blocker:	The suspend blocker to destroy.
> + */
> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
> +{
> +	int flags;
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
> +	flags = atomic_xchg(&blocker->flags, 0);
> +	WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
> +					"uninitialized suspend_blocker\n");
> +	if (flags == (SB_INITIALIZED | SB_ACTIVE))
> +		if (atomic_dec_and_test(&suspend_block_count))
> +			queue_work(suspend_work_queue, &suspend_work);
> +}
> +EXPORT_SYMBOL(suspend_blocker_destroy);
> +
> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
> +	    SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
> +		atomic_inc(&suspend_block_count);
> +
> +	atomic_inc(&current_event_num);
> +}
> +EXPORT_SYMBOL(suspend_block);
> +
> +/**
> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
> +	    SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
> +		if (atomic_dec_and_test(&suspend_block_count))
> +			queue_work(suspend_work_queue, &suspend_work);
> +}
> +EXPORT_SYMBOL(suspend_unblock);
> +
> +/**
> + * is_blocking_suspend() - Test if a suspend blocker is blocking suspend
> + * @blocker:	The suspend blocker to check.
> + */
> +bool is_blocking_suspend(struct suspend_blocker *blocker)
> +{
> +	return !!(atomic_read(&blocker->flags) & SB_ACTIVE);
> +}
> +EXPORT_SYMBOL(is_blocking_suspend);
> +
> +void request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +	spin_lock_irqsave(&state_lock, irqflags);
> +	if (debug_mask & DEBUG_USER_STATE) {
> +		struct timespec ts;
> +		struct rtc_time tm;
> +		getnstimeofday(&ts);
> +		rtc_time_to_tm(ts.tv_sec, &tm);
> +		pr_info("request_suspend_state: %s (%d->%d) at %lld "
> +			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
> +			state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			requested_suspend_state, state,
> +			ktime_to_ns(ktime_get()),
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
> +	}
> +	requested_suspend_state = state;
> +	if (state == PM_SUSPEND_ON)
> +		suspend_block(&main_suspend_blocker);
> +	else
> +		suspend_unblock(&main_suspend_blocker);
> +	spin_unlock_irqrestore(&state_lock, irqflags);
> +}
> +
> +static int __init suspend_block_init(void)
> +{
> +	int ret;
> +
> +	suspend_blocker_init(&main_suspend_blocker, "main");
> +	suspend_block(&main_suspend_blocker);
> +
> +	ret = sysdev_class_register(&suspend_block_sysclass);
> +	if (ret) {
> +		pr_err("suspend_block_init: sysdev_class_register failed\n");
> +		goto err_sysdev_class_register;
> +	}
> +	ret = sysdev_register(&suspend_block_sysdev);
> +	if (ret) {
> +		pr_err("suspend_block_init: suspend_block_sysdev failed\n");
> +		goto err_sysdev_register;
> +	}
> +
> +	suspend_work_queue = create_singlethread_workqueue("suspend");
> +	if (suspend_work_queue == NULL) {
> +		ret = -ENOMEM;
> +		goto err_suspend_work_queue;
> +	}
> +
> +	return 0;
> +
> +err_suspend_work_queue:
> +	sysdev_unregister(&suspend_block_sysdev);
> +err_sysdev_register:
> +	sysdev_class_unregister(&suspend_block_sysclass);
> +err_sysdev_class_register:
> +	suspend_blocker_destroy(&main_suspend_blocker);
> +	return ret;
> +}
> +
> +static void  __exit suspend_block_exit(void)
> +{
> +	destroy_workqueue(suspend_work_queue);
> +	sysdev_unregister(&suspend_block_sysdev);
> +	sysdev_class_unregister(&suspend_block_sysclass);
> +	suspend_blocker_destroy(&main_suspend_blocker);
> +}
> +
> +core_initcall(suspend_block_init);
> +module_exit(suspend_block_exit);
> -- 
> 1.6.1

Re: [RFC][PATCH 0/8] Suspend block api

[Rafael J. Wysocki]

On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
> This patch series adds a suspend-block api that provides the same
> functionality as the android wakelock api from my last patch series,
> Android PM extensions (version 3). As requested, wake_lock has been
> renamed to suspend_block(er), and timeout support has been separated
> into its own patch.

Sounds good.

Unfortunately, I don't have the time to review the patches in detail at the
moment.  Will to that as soon as I can.

Thanks,
Rafael
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Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2009/4/15 Alan Stern <stern@rowland.harvard.edu>:
> On Tue, 14 Apr 2009, [utf-8] Arve Hjønnevåg wrote:
>
>> +Suspend blockers can be used to allow user-space to decide which keys should
>> +wake the full system up and turn the screen on.
>
> This sentence still grates on me.  For readers not familiar with the
> embedded/phone environment, it won't make any sense.  Furthermore the
> rest of the text below doesn't even mention the screen, which will
> cause readers to wonder why it is mentioned here.
>
>>  Use set_irq_wake or a platform
>> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
>> +driver has resumed, the sequence of events can look like this:
>> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
>> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
>> +- The keypad-scan code detects a key change and reports it to the input-event
>> +  driver.
>> +- The input-event driver sees the key change, enqueues an event, and calls
>> +  suspend_block on the input-event-queue suspend_blocker.
>> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
>> +  on the keypad-scan suspend_blocker.
>> +- The user-space input-event thread returns from select/poll, calls
>> +  suspend_block on the process-input-events suspend_blocker and then calls read
>> +  on the input-event device.
>> +- The input-event driver dequeues the key-event and, since the queue is now
>> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
>> +- The user-space input-event thread returns from read. It determines that the
>> +  key should not wake up the full system, calls suspend_unblock on the
>> +  process-input-events suspend_blocker and calls select or poll.
>> +
>> +                 Key pressed   Key released
>> +                     |             |
>> +keypad-scan          ++++++++++++++++++
>> +input-event-queue        +++          +++
>> +process-input-events       +++          +++
>
> How about replacing that first sentence with something like this:
>
>        In cell phones or other embedded systems where powering the
>        screen is a significant drain on the battery, suspend blockers
>        can be used to allow user-space to decide whether a keystroke
>        received while the system is suspended should cause the screen
>        to be turned back on or allow the system to go back into
>        suspend.
>
> Then in the last section, say this:
>
>      - The user-space input-event thread returns from read. If it
>        determines that the key should leave the screen off, it
>        calls suspend_unblock on the process_input_events
>        suspend_blocker and then calls select or poll.  The system
>        will automatically suspend again, since now no suspend blockers
>        are active.
>

This sounds reasonable too me.

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

On Wed, Apr 15, 2009 at 12:08 PM, mark gross <mgross@linux.intel.com> wrote:
> I'm still re-reviewing the design so I probably should keep my mouth
> shut, but I only see code for constraining entry into suspend state (S3
> if you will)  I didn't see code that would get called to block device
> entry into higher power states just constraints on entire system entry
> into sleep state.  (I apologize if I missed that code and will happily
> eat my words if needed.)
>

I removed the idle wake lock type since it had too much overlap with
pm_qos. Are there any references to them left in the documentation?

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2009/4/15 mark gross <mgross@linux.intel.com>:
> I'm sure you are sick of this question, but couldn't you do this same
> functionality (constraining entry to Suspend) using existing
> infrastructure.  You are clearly aggregating a block-count and triggering
> on an zero aggregate value to enter Suspend.

The only reason I have a block count, is that the feedback on this
list was that it is too expensive to use a spin-lock every time we
want to block or unblock suspend. The later patches that enable stats
and timeout support uses inactive and active lists instead.

>
> I'm thinking you could do something like CPUIDLE to push the implicit
> suspend call and use a new pmqos parameter to keep the system alive.
> We'd have to look at the API to make sure it would work in interrupt
> mode.
>
> The only thing I got from the earlier threads asking why not PMQOS, was
> some complaint about the strcmp the constraint aggregation does WRT
> performance.  I don't think it would be too hard to address the perceived
> performance issue (even if its yet to be proven as an issue anywhere)

There was a question about why we did not use pmqos instead othe the
idle wake locks. One reason was that we mainly needed to prevent a
specific state to not loose interrupts, not because the latency was
too high. The other reason was that the pm qos interface uses strings
instead of handles. Using strings to search to a list for the item you
want to update has an impact on performance that is not hard to
measure, but it also require the clients to create unique strings.

> FWIW there is some talk of re-factoring some of pmqos to sit on top of a
> constraint framework (to generalize the code a little and support
> constraining things that are not really measurable in terms of latencies
> or throughputs)
>

That should help with replacing the idle-wake-locks.

> anyway a few comments below.
>
> On Tue, Apr 14, 2009 at 06:41:25PM -0700, Arve Hjønnevåg wrote:
>> Adds /sys/power/request_state, a non-blocking interface that specifies
>> which suspend state to enter when no suspend blockers are active. A
>> special state, "on", stops the process by activating the "main" suspend
>> blocker.
>>
>> Signed-off-by: Arve Hjønnevåg <arve@android.com>
>> ---
>>  Documentation/power/suspend-blockers.txt |   76 +++++++++
>>  include/linux/suspend_block.h            |   61 +++++++
>>  kernel/power/Kconfig                     |   10 ++
>>  kernel/power/Makefile                    |    1 +
>>  kernel/power/main.c                      |   62 +++++++
>>  kernel/power/power.h                     |    6 +
>>  kernel/power/suspend_block.c             |  257 ++++++++++++++++++++++++++++++
>>  7 files changed, 473 insertions(+), 0 deletions(-)
>>  create mode 100644 Documentation/power/suspend-blockers.txt
>>  create mode 100755 include/linux/suspend_block.h
>>  create mode 100644 kernel/power/suspend_block.c
>>
>> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
>> new file mode 100644
>> index 0000000..743b870
>> --- /dev/null
>> +++ b/Documentation/power/suspend-blockers.txt
>> @@ -0,0 +1,76 @@
>> +Suspend blockers
>> +================
>> +
>> +A suspend_blocker prevents the system from entering suspend.
>
> And trigger implicit entry into suspend when last blocker is released.
>
>> +
>> +If the suspend operation has already started when calling suspend_block on a
>> +suspend_blocker, it will abort the suspend operation as long it has not already
>> +reached the sysdev suspend stage. This means that calling suspend_block from an
>> +interrupt handler or a freezeable thread always works, but if you call
>> +block_suspend from a sysdev suspend handler you must also return an error from
>> +that handler to abort suspend.
>> +
>> +Suspend blockers can be used to allow user-space to decide which keys should
>> +wake the full system up and turn the screen on.
>
> Provided the user mode process controlling the screen power is in the calling
> path of user-space input-event thread.

What you mean by this? Our user-space input event thread does not turn
the screen on, but translates the events and queues the translated
event on another queue. As long as all queues are protected by a
suspend blocker, there is no requirement about which thread turns the
screen on.

>
> Basically it should be made clear that this is not a device PM
> implementation.  Its a global system suspend constraint system, where
> the count of blockers is aggregated in a static variable,
> suspend_block_count, within suspend_block.c  with implicit suspend
> called when block count gets to zero.
>
> i.e. only useful in platform specific code for platforms that can do
> ~10ms suspends and resumes.

I disagree. If I have a desktop system that takes 5 seconds to wake up
from sleep, I still want the ability to auto suspend after user
inactivity, and to prevent suspend while some tasks are running.

>
>> Use set_irq_wake or a platform
>> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
>> +driver has resumed, the sequence of events can look like this:
>> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
>> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> count = 1
>> +- The keypad-scan code detects a key change and reports it to the input-event
>> +  driver.
>> +- The input-event driver sees the key change, enqueues an event, and calls
>> +  suspend_block on the input-event-queue suspend_blocker.
> count = 2
>> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
>> +  on the keypad-scan suspend_blocker.
> count = 1
>> +- The user-space input-event thread returns from select/poll, calls
>> +  suspend_block on the process-input-events suspend_blocker and then calls read
>> +  on the input-event device.
> count = 2
>> +- The input-event driver dequeues the key-event and, since the queue is now
>> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> count = 1
>> +- The user-space input-event thread returns from read. It determines that the
>> +  key should not wake up the full system, calls suspend_unblock on the
>> +  process-input-events suspend_blocker and calls select or poll.
> count = 0 + race between dropping into Suspend state and the execution
> of the select or poll.  (should probably be ok)

This is not a race condition, select or poll does not affect the
suspend blocker in the input driver to it does not matter if the poll
is called before or after suspend.

>
>> +
>> +                 Key pressed   Key released
>> +                     |             |
>> +keypad-scan          ++++++++++++++++++
>> +input-event-queue        +++          +++
>> +process-input-events       +++          +++
>> +
>> +

>> +struct suspend_blocker {
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +     atomic_t            flags;
>> +     const char         *name;
>> +#endif
>> +};
>> +
...
>> +
>> +#define SB_INITIALIZED            (1U << 8)
>> +#define SB_ACTIVE                 (1U << 9)
>> +
>> +static DEFINE_SPINLOCK(state_lock);
>> +static atomic_t suspend_block_count;
>
> So if suspend_block_count is the lynch pin of the design, why have all
> the suspend_blocker structs?  Why have all the logic around the
> different suspend blocker instances?

The suspend block structs need to be part of the api to allow stats
and/or debugging. It also ensures that a single suspend_blocker does
not change the global count by more than one. Also,
suspend_block_count is not part of the design, it is an optimization
that becomes useless when you enable stats.

>
> It seems like a lot of extra effort for an atomic "stay awake" counter.
>


-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[mark gross]

On Wed, Apr 15, 2009 at 06:45:00PM -0700, Arve Hjønnevåg wrote:
> 2009/4/15 mark gross <mgross@linux.intel.com>:
> > I'm sure you are sick of this question, but couldn't you do this same
> > functionality (constraining entry to Suspend) using existing
> > infrastructure.  You are clearly aggregating a block-count and triggering
> > on an zero aggregate value to enter Suspend.
> 
> The only reason I have a block count, is that the feedback on this
> list was that it is too expensive to use a spin-lock every time we
> want to block or unblock suspend. The later patches that enable stats
> and timeout support uses inactive and active lists instead.
> 
> >
> > I'm thinking you could do something like CPUIDLE to push the implicit
> > suspend call and use a new pmqos parameter to keep the system alive.
> > We'd have to look at the API to make sure it would work in interrupt
> > mode.
> >
> > The only thing I got from the earlier threads asking why not PMQOS, was
> > some complaint about the strcmp the constraint aggregation does WRT
> > performance.  I don't think it would be too hard to address the perceived
> > performance issue (even if its yet to be proven as an issue anywhere)
> 
> There was a question about why we did not use pmqos instead othe the
> idle wake locks. One reason was that we mainly needed to prevent a
> specific state to not loose interrupts, not because the latency was
> too high. The other reason was that the pm qos interface uses strings
> instead of handles. Using strings to search to a list for the item you
> want to update has an impact on performance that is not hard to
> measure, but it also require the clients to create unique strings.

really?  How many times / second was your system changing the pmqos
parameter?  If that turns out to be realistic, non-abusive use of the api
then perhaps I need to migrate pmqos to include / use handles.  

when pmqos was designed we assumed it wouldn't be hit with high
parameter change rates.  What could be a realistic upper bound on
change rate for the parameters?

> 
> > FWIW there is some talk of re-factoring some of pmqos to sit on top of a
> > constraint framework (to generalize the code a little and support
> > constraining things that are not really measurable in terms of latencies
> > or throughputs)
> >
> 
> That should help with replacing the idle-wake-locks.
> 
> > anyway a few comments below.
> >
> > On Tue, Apr 14, 2009 at 06:41:25PM -0700, Arve Hjønnevåg wrote:
> >> Adds /sys/power/request_state, a non-blocking interface that specifies
> >> which suspend state to enter when no suspend blockers are active. A
> >> special state, "on", stops the process by activating the "main" suspend
> >> blocker.
> >>
> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> >> ---
> >>  Documentation/power/suspend-blockers.txt |   76 +++++++++
> >>  include/linux/suspend_block.h            |   61 +++++++
> >>  kernel/power/Kconfig                     |   10 ++
> >>  kernel/power/Makefile                    |    1 +
> >>  kernel/power/main.c                      |   62 +++++++
> >>  kernel/power/power.h                     |    6 +
> >>  kernel/power/suspend_block.c             |  257 ++++++++++++++++++++++++++++++
> >>  7 files changed, 473 insertions(+), 0 deletions(-)
> >>  create mode 100644 Documentation/power/suspend-blockers.txt
> >>  create mode 100755 include/linux/suspend_block.h
> >>  create mode 100644 kernel/power/suspend_block.c
> >>
> >> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
> >> new file mode 100644
> >> index 0000000..743b870
> >> --- /dev/null
> >> +++ b/Documentation/power/suspend-blockers.txt
> >> @@ -0,0 +1,76 @@
> >> +Suspend blockers
> >> +================
> >> +
> >> +A suspend_blocker prevents the system from entering suspend.
> >
> > And trigger implicit entry into suspend when last blocker is released.
> >
> >> +
> >> +If the suspend operation has already started when calling suspend_block on a
> >> +suspend_blocker, it will abort the suspend operation as long it has not already
> >> +reached the sysdev suspend stage. This means that calling suspend_block from an
> >> +interrupt handler or a freezeable thread always works, but if you call
> >> +block_suspend from a sysdev suspend handler you must also return an error from
> >> +that handler to abort suspend.
> >> +
> >> +Suspend blockers can be used to allow user-space to decide which keys should
> >> +wake the full system up and turn the screen on.
> >
> > Provided the user mode process controlling the screen power is in the calling
> > path of user-space input-event thread.
> 
> What you mean by this? Our user-space input event thread does not turn
> the screen on, but translates the events and queues the translated
> event on another queue. As long as all queues are protected by a
> suspend blocker, there is no requirement about which thread turns the
> screen on.

I mean that to enable the promised partial system wake up ( "Suspend
blockers can be used to allow user-space to decide which keys should
wake the full system up and turn the screen on.") there is more to the
story as this API is about system level pm not device PM needed to keep
the screen off while partially waking things up before suspending again.

Perhaps an explanation on how suspend blocker can be used to partially
wake up a system without the screen coming on would help me.  Right now
I'm not seeing how that can be implemented in the context of this patch.


 
> >
> > Basically it should be made clear that this is not a device PM
> > implementation.  Its a global system suspend constraint system, where
> > the count of blockers is aggregated in a static variable,
> > suspend_block_count, within suspend_block.c  with implicit suspend
> > called when block count gets to zero.
> >
> > i.e. only useful in platform specific code for platforms that can do
> > ~10ms suspends and resumes.
> 
> I disagree. If I have a desktop system that takes 5 seconds to wake up
> from sleep, I still want the ability to auto suspend after user
> inactivity, and to prevent suspend while some tasks are running.

I guess we have this now, but the user mode implementations don't scale
to low latency and frequent suspend applications.


--mgross


> >
> >> Use set_irq_wake or a platform
> >> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
> >> +driver has resumed, the sequence of events can look like this:
> >> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> >> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> > count = 1
> >> +- The keypad-scan code detects a key change and reports it to the input-event
> >> +  driver.
> >> +- The input-event driver sees the key change, enqueues an event, and calls
> >> +  suspend_block on the input-event-queue suspend_blocker.
> > count = 2
> >> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> >> +  on the keypad-scan suspend_blocker.
> > count = 1
> >> +- The user-space input-event thread returns from select/poll, calls
> >> +  suspend_block on the process-input-events suspend_blocker and then calls read
> >> +  on the input-event device.
> > count = 2
> >> +- The input-event driver dequeues the key-event and, since the queue is now
> >> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> > count = 1
> >> +- The user-space input-event thread returns from read. It determines that the
> >> +  key should not wake up the full system, calls suspend_unblock on the
> >> +  process-input-events suspend_blocker and calls select or poll.
> > count = 0 + race between dropping into Suspend state and the execution
> > of the select or poll.  (should probably be ok)
> 
> This is not a race condition, select or poll does not affect the
> suspend blocker in the input driver to it does not matter if the poll
> is called before or after suspend.
> 
> >
> >> +
> >> +                 Key pressed   Key released
> >> +                     |             |
> >> +keypad-scan          ++++++++++++++++++
> >> +input-event-queue        +++          +++
> >> +process-input-events       +++          +++
> >> +
> >> +
> 
> >> +struct suspend_blocker {
> >> +#ifdef CONFIG_SUSPEND_BLOCK
> >> +     atomic_t            flags;
> >> +     const char         *name;
> >> +#endif
> >> +};
> >> +
> ...
> >> +
> >> +#define SB_INITIALIZED            (1U << 8)
> >> +#define SB_ACTIVE                 (1U << 9)
> >> +
> >> +static DEFINE_SPINLOCK(state_lock);
> >> +static atomic_t suspend_block_count;
> >
> > So if suspend_block_count is the lynch pin of the design, why have all
> > the suspend_blocker structs?  Why have all the logic around the
> > different suspend blocker instances?
> 
> The suspend block structs need to be part of the api to allow stats
> and/or debugging. It also ensures that a single suspend_blocker does
> not change the global count by more than one. Also,
> suspend_block_count is not part of the design, it is an optimization
> that becomes useless when you enable stats.
> 
> >
> > It seems like a lot of extra effort for an atomic "stay awake" counter.
> >
> 
> 
> -- 
> Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Pavel Machek]

Hi!


> +Driver API
> +==========
> +
> +A driver can use the suspend block api by adding a suspend_blocker variable to
> +its state and calling suspend_blocker_init. For instance:
> +struct state {
> +	struct suspend_blocker suspend_blocker;
> +}
> +
> +init() {
> +	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
> +}
> +
> +Before freeing the memory, suspend_blocker_destroy must be called:
> +
> +uninit() {
> +	suspend_blocker_destroy(&state->suspend_blocker);
> +}
> +
> +When the driver determines that it needs to run (usually in an interrupt
> +handler) it calls suspend_block:
> +	suspend_block(&state->suspend_blocker);
> +
> +When it no longer needs to run it calls suspend_unblock:
> +	suspend_unblock(&state->suspend_blocker);

Sounds reasonably sane. Maybe it should be block_suspend(), because
suspend_block() sounds like... something that builds suspend, but I
guess it is good enough.

> +/* A suspend_blocker prevents the system from entering suspend when active.
> + */
> +

linuxdoc?

> +struct suspend_blocker {
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	atomic_t            flags;
> +	const char         *name;
> +#endif
> +};
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
> +void suspend_block(struct suspend_blocker *blocker);
> +void suspend_unblock(struct suspend_blocker *blocker);
> +
> +/* is_blocking_suspend returns true if the suspend_blocker is currently active.
> + */
> +bool is_blocking_suspend(struct suspend_blocker *blocker);

Same here?

> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 23bd4da..9d1df13 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -116,6 +116,16 @@ config SUSPEND_FREEZER
>  
>  	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
>  
> +config SUSPEND_BLOCK
> +	bool "Suspend block"
> +	depends on PM
> +	select RTC_LIB

Is RTC_LIB okay to select?

> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>  
>  
>  static const char * const pm_states[PM_SUSPEND_MAX] = {
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	[PM_SUSPEND_ON]		= "on",
> +#endif
>  	[PM_SUSPEND_STANDBY]	= "standby",
>  	[PM_SUSPEND_MEM]	= "mem",
>  };

This allows you to write "on" to the other interfaces where that makes
no sense.... right?

> +static bool enable_suspend_blockers;

Uhuh... What is this good for... except debugging?

> +bool suspend_is_blocked(void)
> +{
> +	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
> +		return 0;
> +	return !!atomic_read(&suspend_block_count);
> +}

Yes, if enable_suspend_blockers is one, we are in deep trouble.

> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in
> + *		/proc/suspend_blockers

I don't think suspend_blockers should go to /proc. They are not process-related.

> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
As blocker->flags seem to be used mostly for debugging; do they have
to use "atomic"? Normally, "magic" variable is used, instead. (Single
bit is probably not enough to guard against using uninitialized
memory.)

> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{

...BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED)); ?

> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
> +	    SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
> +		if (atomic_dec_and_test(&suspend_block_count))
> +			queue_work(suspend_work_queue, &suspend_work);
> +}
> +EXPORT_SYMBOL(suspend_unblock);

Uhuh... can we "loose a oportunity to suspend" here? If someone is
just updating the flags...? Is it guaranteed that if two people do
suspend_unblock at the same time, one of them will pass?

> +void request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +	spin_lock_irqsave(&state_lock, irqflags);
> +	if (debug_mask & DEBUG_USER_STATE) {
> +		struct timespec ts;
> +		struct rtc_time tm;
> +		getnstimeofday(&ts);
> +		rtc_time_to_tm(ts.tv_sec, &tm);
> +		pr_info("request_suspend_state: %s (%d->%d) at %lld "
> +			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
> +			state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			requested_suspend_state, state,
> +			ktime_to_ns(ktime_get()),
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);

Introduce macro for printing time?

Otherwise, it looks good...
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

On Mon, Apr 20, 2009 at 2:29 AM, Pavel Machek <pavel@ucw.cz> wrote:

>> +When the driver determines that it needs to run (usually in an interrupt
>> +handler) it calls suspend_block:
>> +     suspend_block(&state->suspend_blocker);
>> +
>> +When it no longer needs to run it calls suspend_unblock:
>> +     suspend_unblock(&state->suspend_blocker);
>
> Sounds reasonably sane. Maybe it should be block_suspend(), because
> suspend_block() sounds like... something that builds suspend, but I
> guess it is good enough.
>

I was trying to keep a common prefix.

>> +/* A suspend_blocker prevents the system from entering suspend when active.
>> + */
>> +
>
> linuxdoc?
>
>> +struct suspend_blocker {
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +     atomic_t            flags;
>> +     const char         *name;
>> +#endif
>> +};
>> +
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +
>> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
>> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
>> +void suspend_block(struct suspend_blocker *blocker);
>> +void suspend_unblock(struct suspend_blocker *blocker);
>> +
>> +/* is_blocking_suspend returns true if the suspend_blocker is currently active.
>> + */
>> +bool is_blocking_suspend(struct suspend_blocker *blocker);
>
> Same here?

I moved this to the c file, see diff below.

>
>> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
>> index 23bd4da..9d1df13 100644
>> --- a/kernel/power/Kconfig
>> +++ b/kernel/power/Kconfig
>> @@ -116,6 +116,16 @@ config SUSPEND_FREEZER
>>
>>         Turning OFF this setting is NOT recommended! If in doubt, say Y.
>>
>> +config SUSPEND_BLOCK
>> +     bool "Suspend block"
>> +     depends on PM
>> +     select RTC_LIB
>
> Is RTC_LIB okay to select?

It should be. It cannot be enabled manually.

>> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>>
>>
>>  static const char * const pm_states[PM_SUSPEND_MAX] = {
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +     [PM_SUSPEND_ON]         = "on",
>> +#endif
>>       [PM_SUSPEND_STANDBY]    = "standby",
>>       [PM_SUSPEND_MEM]        = "mem",
>>  };
>
> This allows you to write "on" to the other interfaces where that makes
> no sense.... right?

state_store starts iterating at PM_SUSPEND_STANDBY, so don't think so.

>
>> +static bool enable_suspend_blockers;
>
> Uhuh... What is this good for... except debugging?

It prevents suspend blockers from affecting existing suspend and
freezing interfaces (while auto suspend is not active).

>
>> +bool suspend_is_blocked(void)
>> +{
>> +     if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
>> +             return 0;
>> +     return !!atomic_read(&suspend_block_count);
>> +}
>
> Yes, if enable_suspend_blockers is one, we are in deep trouble.

It just means that you compiled suspend blocker support into the
kernel, but used an old interface to enter suspend. It warns if
enable_suspend_blockers is 0 not 1.

>
>> +/**
>> + * suspend_blocker_init() - Initialize a suspend blocker
>> + * @blocker: The suspend blocker to initialize.
>> + * @name:    The name of the suspend blocker to show in
>> + *           /proc/suspend_blockers
>
> I don't think suspend_blockers should go to /proc. They are not process-related.

I moved that comment to the stats patch. It is still in procfs though,
as it is most similar to other procfs entries. It is not allowed under
the sysfs rules, and we do not want to enable debugfs on a production
system since it exposes some unsafe interfaces.

>
>> +/**
>> + * suspend_block() - Block suspend
>> + * @blocker: The suspend blocker to use
>> + */
>> +void suspend_block(struct suspend_blocker *blocker)
>> +{
>> +     BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
> As blocker->flags seem to be used mostly for debugging; do they have
> to use "atomic"? Normally, "magic" variable is used, instead. (Single
> bit is probably not enough to guard against using uninitialized
> memory.)

It is mostly used to determine if the suspend blocker is already
active, so yes it has to be atomic. I could add a magic value, but a
single bit is enough to catch uninitialized global and kzalloced
members.

>
>> + * suspend_unblock() - Unblock suspend
>> + * @blocker: The suspend blocker to unblock.
>> + *
>> + * If no other suspend blockers block suspend, the system will suspend.
>> + */
>> +void suspend_unblock(struct suspend_blocker *blocker)
>> +{
>
> ...BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED)); ?

Perhaps. This function does not do anything unless you have already
called suspend_block though.

>
>> +     if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> +             pr_info("suspend_unblock: %s\n", blocker->name);
>> +
>> +     if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
>> +         SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
>> +             if (atomic_dec_and_test(&suspend_block_count))
>> +                     queue_work(suspend_work_queue, &suspend_work);
>> +}
>> +EXPORT_SYMBOL(suspend_unblock);
>
> Uhuh... can we "loose a oportunity to suspend" here? If someone is
> just updating the flags...? Is it guaranteed that if two people do
> suspend_unblock at the same time, one of them will pass?

What do you mean by just updating the flags? SB_ACTIVE was either
cleared or not, if it was, then atomic_dec_and_test is called.

>
>> +void request_suspend_state(suspend_state_t state)
>> +{
>> +     unsigned long irqflags;
>> +     spin_lock_irqsave(&state_lock, irqflags);
>> +     if (debug_mask & DEBUG_USER_STATE) {
>> +             struct timespec ts;
>> +             struct rtc_time tm;
>> +             getnstimeofday(&ts);
>> +             rtc_time_to_tm(ts.tv_sec, &tm);
>> +             pr_info("request_suspend_state: %s (%d->%d) at %lld "
>> +                     "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
>> +                     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
>> +                     requested_suspend_state, state,
>> +                     ktime_to_ns(ktime_get()),
>> +                     tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
>> +                     tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
>
> Introduce macro for printing time?

OK.

-- 
Arve Hjønnevåg

----
diff --git a/Documentation/power/suspend-blockers.txt
b/Documentation/power/suspend-blockers.txt
index 743b870..e95a507 100644
--- a/Documentation/power/suspend-blockers.txt
+++ b/Documentation/power/suspend-blockers.txt
@@ -10,10 +10,14 @@ interrupt handler or a freezeable thread always
works, but if you call
 block_suspend from a sysdev suspend handler you must also return an error from
 that handler to abort suspend.

-Suspend blockers can be used to allow user-space to decide which keys should
-wake the full system up and turn the screen on. Use set_irq_wake or a platform
-specific api to make sure the keypad interrupt wakes up the cpu. Once
the keypad
-driver has resumed, the sequence of events can look like this:
+In cell phones or other embedded systems where powering the screen is a
+significant drain on the battery, suspend blockers can be used to allow
+user-space to decide whether a keystroke received while the system is suspended
+should cause the screen to be turned back on or allow the system to
go back into
+suspend. Use set_irq_wake or a platform specific api to make sure the keypad
+interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
+events can look like this:
+
 - The Keypad driver gets an interrupt. It then calls suspend_block on the
   keypad-scan suspend_blocker and starts scanning the keypad matrix.
 - The keypad-scan code detects a key change and reports it to the input-event
@@ -27,9 +31,11 @@ driver has resumed, the sequence of events can look
like this:
   on the input-event device.
 - The input-event driver dequeues the key-event and, since the queue is now
   empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
-- The user-space input-event thread returns from read. It determines that the
-  key should not wake up the full system, calls suspend_unblock on the
-  process-input-events suspend_blocker and calls select or poll.
+- The user-space input-event thread returns from read. If it determines that
+  the key should leave the screen off, it calls suspend_unblock on the
+  process_input_events suspend_blocker and then calls select or poll. The
+  system will automatically suspend again, since now no suspend blockers are
+  active.

                  Key pressed   Key released
                      |             |
diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
index 7820c60..54bf9c4 100755
--- a/include/linux/suspend_block.h
+++ b/include/linux/suspend_block.h
@@ -16,7 +16,15 @@
 #ifndef _LINUX_SUSPEND_BLOCK_H
 #define _LINUX_SUSPEND_BLOCK_H

-/* A suspend_blocker prevents the system from entering suspend when active.
+/**
+ * struct suspend_blocker - the basic suspend_blocker structure
+ * @flags:     Tracks initialized and active state.
+ * @name:      Name used for debugging.
+ *
+ * When a suspend_blocker is active it prevents the system from entering
+ * suspend.
+ *
+ * The suspend_blocker structure must be initialized by suspend_blocker_init()
  */

 struct suspend_blocker {
@@ -32,17 +40,7 @@ void suspend_blocker_init(struct suspend_blocker
*blocker, const char *name);
 void suspend_blocker_destroy(struct suspend_blocker *blocker);
 void suspend_block(struct suspend_blocker *blocker);
 void suspend_unblock(struct suspend_blocker *blocker);
-
-/* is_blocking_suspend returns true if the suspend_blocker is currently active.
- */
 bool is_blocking_suspend(struct suspend_blocker *blocker);
-
-/* suspend_is_blocked can be used by generic power management code to abort
- * suspend.
- *
- * To preserve backward compatibility suspend_is_blocked returns 0 unless it
- * is called during suspend initiated from the suspend_block code.
- */
 bool suspend_is_blocked(void);

 #else
diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
index b4f2191..1adf075 100644
--- a/kernel/power/suspend_block.c
+++ b/kernel/power/suspend_block.c
@@ -41,6 +41,27 @@ struct suspend_blocker main_suspend_blocker;
 static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
 static bool enable_suspend_blockers;

+#define pr_info_time(fmt, args...) \
+       do { \
+               struct timespec ts; \
+               struct rtc_time tm; \
+               getnstimeofday(&ts); \
+               rtc_time_to_tm(ts.tv_sec, &tm); \
+               pr_info(fmt "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n" , \
+                       args, \
+                       tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, \
+                       tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
+       } while (0);
+
+/**
+ * suspend_is_blocked() - Check if suspend should be blocked
+ *
+ * suspend_is_blocked can be used by generic power management code to abort
+ * suspend.
+ *
+ * To preserve backward compatibility suspend_is_blocked returns 0 unless it
+ * is called during suspend initiated from the suspend_block code.
+ */
 bool suspend_is_blocked(void)
 {
        if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
@@ -66,16 +87,8 @@ retry:
        if (debug_mask & DEBUG_SUSPEND)
                pr_info("suspend: enter suspend\n");
        ret = pm_suspend(requested_suspend_state);
-       if (debug_mask & DEBUG_EXIT_SUSPEND) {
-               struct timespec ts;
-               struct rtc_time tm;
-               getnstimeofday(&ts);
-               rtc_time_to_tm(ts.tv_sec, &tm);
-               pr_info("suspend: exit suspend, ret = %d "
-                       "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
-                       tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
-                       tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
-       }
+       if (debug_mask & DEBUG_EXIT_SUSPEND)
+               pr_info_time("suspend: exit suspend, ret = %d ", ret);
        if (atomic_read(&current_event_num) == entry_event_num) {
                if (debug_mask & DEBUG_SUSPEND)
                        pr_info("suspend: pm_suspend returned with no event\n");
@@ -105,8 +118,7 @@ static struct sys_device suspend_block_sysdev = {
 /**
  * suspend_blocker_init() - Initialize a suspend blocker
  * @blocker:   The suspend blocker to initialize.
- * @name:      The name of the suspend blocker to show in
- *             /proc/suspend_blockers
+ * @name:      The name of the suspend blocker to show in debug messages.
  */
 void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
 {
@@ -178,6 +190,8 @@ EXPORT_SYMBOL(suspend_unblock);
 /**
  * is_blocking_suspend() - Test if a suspend blocker is blocking suspend
  * @blocker:   The suspend blocker to check.
+ *
+ * Returns true if the suspend_blocker is currently active.
  */
 bool is_blocking_suspend(struct suspend_blocker *blocker)
 {
@@ -189,19 +203,11 @@ void request_suspend_state(suspend_state_t state)
 {
        unsigned long irqflags;
        spin_lock_irqsave(&state_lock, irqflags);
-       if (debug_mask & DEBUG_USER_STATE) {
-               struct timespec ts;
-               struct rtc_time tm;
-               getnstimeofday(&ts);
-               rtc_time_to_tm(ts.tv_sec, &tm);
-               pr_info("request_suspend_state: %s (%d->%d) at %lld "
-                       "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
-                       state != PM_SUSPEND_ON ? "sleep" : "wakeup",
-                       requested_suspend_state, state,
-                       ktime_to_ns(ktime_get()),
-                       tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
-                       tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
-       }
+       if (debug_mask & DEBUG_USER_STATE)
+               pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
+                            state != PM_SUSPEND_ON ? "sleep" : "wakeup",
+                            requested_suspend_state, state,
+                            ktime_to_ns(ktime_get()));
        requested_suspend_state = state;
        if (state == PM_SUSPEND_ON)
                suspend_block(&main_suspend_blocker);

Re: [PATCH 1/8] PM: Add suspend block api.

[Pavel Machek]

Hi!

> >> @@ -392,6 +393,9 @@ static void suspend_finish(void)
> >>
> >>
> >>  static const char * const pm_states[PM_SUSPEND_MAX] = {
> >> +#ifdef CONFIG_SUSPEND_BLOCK
> >> +     [PM_SUSPEND_ON]         = "on",
> >> +#endif
> >>       [PM_SUSPEND_STANDBY]    = "standby",
> >>       [PM_SUSPEND_MEM]        = "mem",
> >>  };
> >
> > This allows you to write "on" to the other interfaces where that makes
> > no sense.... right?
> 
> state_store starts iterating at PM_SUSPEND_STANDBY, so don't think so.

Good.


> >> +bool suspend_is_blocked(void)
> >> +{
> >> +     if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
> >> +             return 0;
> >> +     return !!atomic_read(&suspend_block_count);
> >> +}
> >
> > Yes, if enable_suspend_blockers is one, we are in deep trouble.
> 
> It just means that you compiled suspend blocker support into the
> kernel, but used an old interface to enter suspend. It warns if
> enable_suspend_blockers is 0 not 1.

I do not think WARN_ONCE() should be that easy to trigger. WARN is
very scary animal; better use normal printk?



> >> +/**
> >> + * suspend_blocker_init() - Initialize a suspend blocker
> >> + * @blocker: The suspend blocker to initialize.
> >> + * @name:    The name of the suspend blocker to show in
> >> + *           /proc/suspend_blockers
> >
> > I don't think suspend_blockers should go to /proc. They are not process-related.
> 
> I moved that comment to the stats patch. It is still in procfs though,
> as it is most similar to other procfs entries. It is not allowed under
> the sysfs rules, and we do not want to enable debugfs on a production
> system since it exposes some unsafe interfaces.

You have to sort this out somehow. It does not belong to /proc.

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 1/8] PM: Add suspend block api.

[Pavel Machek]

Hi!

> >> --- a/kernel/power/power.h
> >> +++ b/kernel/power/power.h
> >> @@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
> >>  {
> >>  }
> >>  #endif
> >> +
> >> +#ifdef CONFIG_SUSPEND_BLOCK
> >> +/* kernel/power/suspend_block.c */
> >> +void request_suspend_state(suspend_state_t state);
> >> +#endif
> >
> > Is the #ifdef really necessary?
> >
> 
> No, but it gives a compile error instead of a link error if you call
> request_suspend_state when it is not available so it is useful.

I believe #ifdef is too ugly and link error is really good enough.

  	  	    	     	      	       	      	   Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Friday 24 April 2009, Pavel Machek wrote:
> Hi!
> 
> > >> @@ -392,6 +393,9 @@ static void suspend_finish(void)
> > >>
> > >>
> > >>  static const char * const pm_states[PM_SUSPEND_MAX] = {
> > >> +#ifdef CONFIG_SUSPEND_BLOCK
> > >> +     [PM_SUSPEND_ON]         = "on",
> > >> +#endif
> > >>       [PM_SUSPEND_STANDBY]    = "standby",
> > >>       [PM_SUSPEND_MEM]        = "mem",
> > >>  };
> > >
> > > This allows you to write "on" to the other interfaces where that makes
> > > no sense.... right?
> > 
> > state_store starts iterating at PM_SUSPEND_STANDBY, so don't think so.
> 
> Good.
> 
> 
> > >> +bool suspend_is_blocked(void)
> > >> +{
> > >> +     if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
> > >> +             return 0;
> > >> +     return !!atomic_read(&suspend_block_count);
> > >> +}
> > >
> > > Yes, if enable_suspend_blockers is one, we are in deep trouble.
> > 
> > It just means that you compiled suspend blocker support into the
> > kernel, but used an old interface to enter suspend. It warns if
> > enable_suspend_blockers is 0 not 1.
> 
> I do not think WARN_ONCE() should be that easy to trigger. WARN is
> very scary animal; better use normal printk?

Yes, printk() please.

> > >> +/**
> > >> + * suspend_blocker_init() - Initialize a suspend blocker
> > >> + * @blocker: The suspend blocker to initialize.
> > >> + * @name:    The name of the suspend blocker to show in
> > >> + *           /proc/suspend_blockers
> > >
> > > I don't think suspend_blockers should go to /proc. They are not process-related.
> > 
> > I moved that comment to the stats patch. It is still in procfs though,
> > as it is most similar to other procfs entries. It is not allowed under
> > the sysfs rules, and we do not want to enable debugfs on a production
> > system since it exposes some unsafe interfaces.
> 
> You have to sort this out somehow. It does not belong to /proc.

Agreed.

Thanks,
Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
> Adds /sys/power/request_state, a non-blocking interface that specifies
> which suspend state to enter when no suspend blockers are active. A
> special state, "on", stops the process by activating the "main" suspend
> blocker.

Finally I have some time to look at this more thoroughly, sorry for the long
delay.

I'll try not to repeate the others' comments, but I guess that may not be
totally avoidable.

> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ---
>  Documentation/power/suspend-blockers.txt |   76 +++++++++
>  include/linux/suspend_block.h            |   61 +++++++
>  kernel/power/Kconfig                     |   10 ++
>  kernel/power/Makefile                    |    1 +
>  kernel/power/main.c                      |   62 +++++++
>  kernel/power/power.h                     |    6 +
>  kernel/power/suspend_block.c             |  257 ++++++++++++++++++++++++++++++
>  7 files changed, 473 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/power/suspend-blockers.txt
>  create mode 100755 include/linux/suspend_block.h
>  create mode 100644 kernel/power/suspend_block.c
> 
> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
> new file mode 100644
> index 0000000..743b870
> --- /dev/null
> +++ b/Documentation/power/suspend-blockers.txt
> @@ -0,0 +1,76 @@
> +Suspend blockers
> +================
> +
> +A suspend_blocker prevents the system from entering suspend.

I'd say "suspend blocker", without the underscore.

Also, I'd try to provide a general explanation of how this is supposed to
work here, as an introduction.  Something like:

"Suspend blockers provide a mechanism allowing device drivers and user
space processes to prevent the system from entering a sleep state, such as
the ACPI S3 state.

To use a suspend blocker, a device driver needs a struct suspend_blocker object
that has to be initialized with the help of suspend_blocker_init().  When no
longer needed, the suspend blocker must be garbage collected with the help
of suspend_blocker_destroy().

A suspend blocker is activated using suspend_block(), which prevents the
system from entering any sleep state until the suspend blocker is deactivated
with suspend_unblock().  Many suspend blockers may be used simultaneously
and the system is prevented from entering sleep states as long as at least one
of them is active."

BTW, I don't really like the names "suspend_block" and "suspend_unblock".
See below for possible alternatives.

> +If the suspend operation has already started when calling suspend_block on a
> +suspend_blocker, it will abort the suspend operation as long it has not already
> +reached the sysdev suspend stage. This means that calling suspend_block from an
> +interrupt handler or a freezeable thread always works, but if you call
> +block_suspend

Surely suspend_block() ?

> from a sysdev suspend handler you must also return an error from
> +that handler to abort suspend.

Well, if a sysdev suspend handler returns an error code, suspend will be
aborted anyway, so I'm not sure what the point in using suspend blockers from
sysdev suspend handlers really is.  Perhaps it's better to say "don't use
suspend blockers from withing sysdev suspend handlers"?

> +

I'd say "For example" here.

> +Suspend blockers can be used to allow user-space to decide which keys should
> +wake the full system up and turn the screen on. Use set_irq_wake or a platform
> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
> +driver has resumed, the sequence of events can look like this:
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> +- The user-space input-event thread returns from read. It determines that the
> +  key should not wake up the full system, calls suspend_unblock on the
> +  process-input-events suspend_blocker and calls select or poll.
> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++
> +
> +
> +Driver API
> +==========
> +
> +A driver can use the suspend block api by adding a suspend_blocker variable to
> +its state and calling suspend_blocker_init. For instance:
> +struct state {
> +	struct suspend_blocker suspend_blocker;
> +}
> +
> +init() {
> +	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
> +}
> +
> +Before freeing the memory, suspend_blocker_destroy must be called:
> +
> +uninit() {
> +	suspend_blocker_destroy(&state->suspend_blocker);
> +}
> +
> +When the driver determines that it needs to run (usually in an interrupt
> +handler) it calls suspend_block:
> +	suspend_block(&state->suspend_blocker);

suspend_blocker_activate() ?
suspend_blocker_enable() ?
suspend_blocker_start() ?

> +
> +When it no longer needs to run it calls suspend_unblock:
> +	suspend_unblock(&state->suspend_blocker);

suspend_blocker_deactivate() ?
suspend_blocker_disable() ?
suspend_blocker_finish() ?

> +
> +Calling suspend_block when the suspend blocker is active or suspend_unblock when
> +it is not active has no effect. This allows drivers to update their state and
> +call suspend suspend_block or suspend_unblock based on the result.
> +For instance:
> +
> +if (list_empty(&state->pending_work))
> +	suspend_unblock(&state->suspend_blocker);
> +else
> +	suspend_block(&state->suspend_blocker);
> +
> diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
> new file mode 100755
> index 0000000..7820c60
> --- /dev/null
> +++ b/include/linux/suspend_block.h

suspend_blockers.h perhaps?

> @@ -0,0 +1,61 @@
> +/* include/linux/suspend_block.h
> + *
> + * Copyright (C) 2007-2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef _LINUX_SUSPEND_BLOCK_H
> +#define _LINUX_SUSPEND_BLOCK_H

SUSPEND_BLOCKERS_H ?

> +
> +/* A suspend_blocker prevents the system from entering suspend when active.
> + */
> +
> +struct suspend_blocker {
> +#ifdef CONFIG_SUSPEND_BLOCK

CONFIG_SUSPEND_BLOCKERS ?

> +	atomic_t            flags;
> +	const char         *name;
> +#endif
> +};
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
> +void suspend_block(struct suspend_blocker *blocker);
> +void suspend_unblock(struct suspend_blocker *blocker);
> +
> +/* is_blocking_suspend returns true if the suspend_blocker is currently active.
> + */
> +bool is_blocking_suspend(struct suspend_blocker *blocker);

suspend_blocker_is_active() ?
suspend_blocker_enabled() ?

> +
> +/* suspend_is_blocked can be used by generic power management code to abort
> + * suspend.
> + *
> + * To preserve backward compatibility suspend_is_blocked returns 0 unless it
> + * is called during suspend initiated from the suspend_block code.
> + */
> +bool suspend_is_blocked(void);
> +
> +#else
> +
> +static inline void suspend_blocker_init(struct suspend_blocker *blocker,
> +					const char *name) {}
> +static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
> +static inline void suspend_block(struct suspend_blocker *blocker) {}
> +static inline void suspend_unblock(struct suspend_blocker *blocker) {}
> +static inline bool is_blocking_suspend(struct suspend_blocker *bl) { return 0; }
> +static inline bool suspend_is_blocked(void) { return 0; }
> +
> +#endif
> +
> +#endif
> +
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 23bd4da..9d1df13 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -116,6 +116,16 @@ config SUSPEND_FREEZER
>  
>  	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
>  
> +config SUSPEND_BLOCK
> +	bool "Suspend block"
> +	depends on PM
> +	select RTC_LIB

depends on RTC_LIB

select doesn't really work and I don't think it ever will.

> +	default n
> +	---help---
> +	  Enable suspend_block.

Enable suspend blockers.

> When user space requests a sleep state through
> +	  /sys/power/request_state, the requested sleep state will be entered
> +	  when no suspend_blockers are active.

Well, if you don't want suspend blockers to block suspend started via
/sys/power/state, it's worth making it crystal clear in the documentation too.

> +
>  config HIBERNATION
>  	bool "Hibernation (aka 'suspend to disk')"
>  	depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
> index 720ea4f..29cdc9e 100644
> --- a/kernel/power/Makefile
> +++ b/kernel/power/Makefile
> @@ -6,6 +6,7 @@ endif
>  obj-$(CONFIG_PM)		+= main.o
>  obj-$(CONFIG_PM_SLEEP)		+= console.o
>  obj-$(CONFIG_FREEZER)		+= process.o
> +obj-$(CONFIG_SUSPEND_BLOCK)	+= suspend_block.o
>  obj-$(CONFIG_HIBERNATION)	+= swsusp.o disk.o snapshot.o swap.o user.o
>  
>  obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index c9632f8..e4c6b20 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -22,6 +22,7 @@
>  #include <linux/freezer.h>
>  #include <linux/vmstat.h>
>  #include <linux/syscalls.h>
> +#include <linux/suspend_block.h>
>  
>  #include "power.h"
>  
> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>  
>  
>  static const char * const pm_states[PM_SUSPEND_MAX] = {
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	[PM_SUSPEND_ON]		= "on",
> +#endif

Why #ifdef?

>  	[PM_SUSPEND_STANDBY]	= "standby",
>  	[PM_SUSPEND_MEM]	= "mem",
>  };
> @@ -540,6 +544,61 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  
>  power_attr(state);
>  
> +/**
> + *	request_state - control system power state.
> + *
> + *	This is similar to state, but it does not block until the system
> + *	resumes, and it will try to re-enter the state until another state is
> + *	requested. Suspend blockers are respected and the requested state will
> + *	only be entered when no suspend blockers are active.
> + *	Write "on" to cancel.
> + */
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +static ssize_t request_state_show(struct kobject *kobj,
> +				  struct kobj_attribute *attr, char *buf)
> +{
> +	char *s = buf;
> +	int i;
> +
> +	for (i = 0; i < PM_SUSPEND_MAX; i++) {
> +		if (pm_states[i] && (i == PM_SUSPEND_ON || valid_state(i)))
> +			s += sprintf(s, "%s ", pm_states[i]);
> +	}
> +	if (s != buf)
> +		/* convert the last space to a newline */
> +		*(s-1) = '\n';
> +	return (s - buf);
> +}
> +
> +static ssize_t request_state_store(struct kobject *kobj,
> +				   struct kobj_attribute *attr,
> +				   const char *buf, size_t n)
> +{
> +	suspend_state_t state = PM_SUSPEND_ON;
> +	const char * const *s;
> +	char *p;
> +	int len;
> +	int error = -EINVAL;
> +
> +	p = memchr(buf, '\n', n);
> +	len = p ? p - buf : n;
> +
> +	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
> +		if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
> +			break;
> +	}
> +	if (state < PM_SUSPEND_MAX && *s)
> +		if (state == PM_SUSPEND_ON || valid_state(state)) {
> +			error = 0;
> +			request_suspend_state(state);
> +		}
> +	return error ? error : n;
> +}
> +
> +power_attr(request_state);
> +#endif /* CONFIG_SUSPEND_BLOCK */
> +
>  #ifdef CONFIG_PM_TRACE
>  int pm_trace_enabled;
>  
> @@ -567,6 +626,9 @@ power_attr(pm_trace);
>  
>  static struct attribute * g[] = {
>  	&state_attr.attr,
> +#ifdef CONFIG_SUSPEND_BLOCK
> +	&request_state_attr.attr,
> +#endif
>  #ifdef CONFIG_PM_TRACE
>  	&pm_trace_attr.attr,
>  #endif
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 46b5ec7..2414a74 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
>  {
>  }
>  #endif
> +
> +#ifdef CONFIG_SUSPEND_BLOCK
> +/* kernel/power/suspend_block.c */
> +void request_suspend_state(suspend_state_t state);
> +#endif

Is the #ifdef really necessary?

> +
> diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
> new file mode 100644
> index 0000000..b4f2191
> --- /dev/null
> +++ b/kernel/power/suspend_block.c
> @@ -0,0 +1,257 @@
> +/* kernel/power/suspend_block.c
> + *
> + * Copyright (C) 2005-2008 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/rtc.h>
> +#include <linux/suspend.h>
> +#include <linux/suspend_block.h>
> +#include <linux/sysdev.h>
> +#include "power.h"
> +
> +enum {
> +	DEBUG_EXIT_SUSPEND = 1U << 0,
> +	DEBUG_WAKEUP = 1U << 1,
> +	DEBUG_USER_STATE = 1U << 2,
> +	DEBUG_SUSPEND = 1U << 3,
> +	DEBUG_SUSPEND_BLOCKER = 1U << 4,
> +};
> +static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +#define SB_INITIALIZED            (1U << 8)
> +#define SB_ACTIVE                 (1U << 9)
> +
> +static DEFINE_SPINLOCK(state_lock);
> +static atomic_t suspend_block_count;
> +static atomic_t current_event_num;
> +struct workqueue_struct *suspend_work_queue;
> +struct suspend_blocker main_suspend_blocker;
> +static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
> +static bool enable_suspend_blockers;
> +
> +bool suspend_is_blocked(void)
> +{
> +	if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
> +		return 0;
> +	return !!atomic_read(&suspend_block_count);
> +}
> +
> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = 1;

'true' instead of '1', please.

> +
> +retry:
> +	if (suspend_is_blocked()) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: abort suspend\n");
> +		goto abort;

If that were in a loop you could just use 'break' here.

> +	}
> +
> +	entry_event_num = atomic_read(&current_event_num);
> +	if (debug_mask & DEBUG_SUSPEND)
> +		pr_info("suspend: enter suspend\n");
> +	ret = pm_suspend(requested_suspend_state);
> +	if (debug_mask & DEBUG_EXIT_SUSPEND) {
> +		struct timespec ts;
> +		struct rtc_time tm;
> +		getnstimeofday(&ts);
> +		rtc_time_to_tm(ts.tv_sec, &tm);
> +		pr_info("suspend: exit suspend, ret = %d "
> +			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
> +	}
> +	if (atomic_read(&current_event_num) == entry_event_num) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: pm_suspend returned with no event\n");
> +		goto retry;

Put that into a loop and use 'continue' here?  Or use 'break' to go out of
the loop?

> +	}
> +abort:
> +	enable_suspend_blockers = 0;

'false' instead of '0', please.

> +}
> +static DECLARE_WORK(suspend_work, suspend_worker);
> +
> +static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
> +{
> +	int ret = suspend_is_blocked() ? -EAGAIN : 0;
> +	if (debug_mask & DEBUG_SUSPEND)
> +		pr_info("suspend_block_suspend return %d\n", ret);
> +	return ret;
> +}
> +
> +static struct sysdev_class suspend_block_sysclass = {
> +	.name = "suspend_block",
> +	.suspend = suspend_block_suspend,
> +};
> +static struct sys_device suspend_block_sysdev = {
> +	.cls = &suspend_block_sysclass,
> +};
> +

Hmm.  Perhaps add the suspend_is_blocked() check at the beginning of
sysdev_suspend() instead of this?  Surely you don't want to suspend
any sysdevs with any suspend blockers active, right?

> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in
> + *		/proc/suspend_blockers
> + */
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
> +{
> +	if (name)
> +		blocker->name = name;
> +	BUG_ON(!blocker->name);

Do you really want to crash the kernel in this case?  WARN_ON() might be better IMO.

Also, this assumes that the caller won't release the memory used to store the
'name' string.  it might be a good idea to point that out in the kerneldoc
comment.

> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_init name=%s\n", blocker->name);
> +
> +	atomic_set(&blocker->flags, SB_INITIALIZED);
> +}
> +EXPORT_SYMBOL(suspend_blocker_init);
> +
> +/**
> + * suspend_blocker_destroy() - Destroy a suspend blocker
> + * @blocker:	The suspend blocker to destroy.
> + */
> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
> +{
> +	int flags;
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
> +	flags = atomic_xchg(&blocker->flags, 0);
> +	WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
> +					"uninitialized suspend_blocker\n");
> +	if (flags == (SB_INITIALIZED | SB_ACTIVE))
> +		if (atomic_dec_and_test(&suspend_block_count))
> +			queue_work(suspend_work_queue, &suspend_work);
> +}
> +EXPORT_SYMBOL(suspend_blocker_destroy);
> +
> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));

WARN_ON() and exit instead?  BUG_ON() is a bit drastic IMHO.

> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
> +	    SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
> +		atomic_inc(&suspend_block_count);
> +
> +	atomic_inc(&current_event_num);
> +}
> +EXPORT_SYMBOL(suspend_block);
> +
> +/**
> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
> +	    SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
> +		if (atomic_dec_and_test(&suspend_block_count))
> +			queue_work(suspend_work_queue, &suspend_work);
> +}
> +EXPORT_SYMBOL(suspend_unblock);
> +
> +/**
> + * is_blocking_suspend() - Test if a suspend blocker is blocking suspend
> + * @blocker:	The suspend blocker to check.
> + */
> +bool is_blocking_suspend(struct suspend_blocker *blocker)
> +{
> +	return !!(atomic_read(&blocker->flags) & SB_ACTIVE);

Check SB_INITIALIZED too, perhaps?  WARN_ON(!SB_INITIALIZED)?

> +}
> +EXPORT_SYMBOL(is_blocking_suspend);
> +
> +void request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +	spin_lock_irqsave(&state_lock, irqflags);
> +	if (debug_mask & DEBUG_USER_STATE) {
> +		struct timespec ts;
> +		struct rtc_time tm;
> +		getnstimeofday(&ts);
> +		rtc_time_to_tm(ts.tv_sec, &tm);
> +		pr_info("request_suspend_state: %s (%d->%d) at %lld "
> +			"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
> +			state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			requested_suspend_state, state,
> +			ktime_to_ns(ktime_get()),
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
> +	}
> +	requested_suspend_state = state;
> +	if (state == PM_SUSPEND_ON)
> +		suspend_block(&main_suspend_blocker);
> +	else
> +		suspend_unblock(&main_suspend_blocker);
> +	spin_unlock_irqrestore(&state_lock, irqflags);
> +}
> +
> +static int __init suspend_block_init(void)
> +{
> +	int ret;
> +
> +	suspend_blocker_init(&main_suspend_blocker, "main");
> +	suspend_block(&main_suspend_blocker);
> +
> +	ret = sysdev_class_register(&suspend_block_sysclass);
> +	if (ret) {
> +		pr_err("suspend_block_init: sysdev_class_register failed\n");
> +		goto err_sysdev_class_register;
> +	}
> +	ret = sysdev_register(&suspend_block_sysdev);
> +	if (ret) {
> +		pr_err("suspend_block_init: suspend_block_sysdev failed\n");
> +		goto err_sysdev_register;
> +	}
> +
> +	suspend_work_queue = create_singlethread_workqueue("suspend");

Do we need a separate workqueue for this purpose?

> +	if (suspend_work_queue == NULL) {
> +		ret = -ENOMEM;
> +		goto err_suspend_work_queue;
> +	}
> +
> +	return 0;
> +
> +err_suspend_work_queue:
> +	sysdev_unregister(&suspend_block_sysdev);
> +err_sysdev_register:
> +	sysdev_class_unregister(&suspend_block_sysclass);
> +err_sysdev_class_register:
> +	suspend_blocker_destroy(&main_suspend_blocker);
> +	return ret;
> +}
> +
> +static void  __exit suspend_block_exit(void)
> +{
> +	destroy_workqueue(suspend_work_queue);
> +	sysdev_unregister(&suspend_block_sysdev);
> +	sysdev_class_unregister(&suspend_block_sysclass);
> +	suspend_blocker_destroy(&main_suspend_blocker);
> +}
> +
> +core_initcall(suspend_block_init);
> +module_exit(suspend_block_exit);

Thanks,
Rafael
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Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

On Wed, Apr 29, 2009 at 2:24 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Friday 24 April 2009, Pavel Machek wrote:
>> Hi!
>>
>> > >> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>> > >>
>> > >>
>> > >>  static const char * const pm_states[PM_SUSPEND_MAX] = {
>> > >> +#ifdef CONFIG_SUSPEND_BLOCK
>> > >> +     [PM_SUSPEND_ON]         = "on",
>> > >> +#endif
>> > >>       [PM_SUSPEND_STANDBY]    = "standby",
>> > >>       [PM_SUSPEND_MEM]        = "mem",
>> > >>  };
>> > >
>> > > This allows you to write "on" to the other interfaces where that makes
>> > > no sense.... right?
>> >
>> > state_store starts iterating at PM_SUSPEND_STANDBY, so don't think so.
>>
>> Good.
>>
>>
>> > >> +bool suspend_is_blocked(void)
>> > >> +{
>> > >> +     if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
>> > >> +             return 0;
>> > >> +     return !!atomic_read(&suspend_block_count);
>> > >> +}
>> > >
>> > > Yes, if enable_suspend_blockers is one, we are in deep trouble.
>> >
>> > It just means that you compiled suspend blocker support into the
>> > kernel, but used an old interface to enter suspend. It warns if
>> > enable_suspend_blockers is 0 not 1.
>>
>> I do not think WARN_ONCE() should be that easy to trigger. WARN is
>> very scary animal; better use normal printk?
>
> Yes, printk() please.

Using printk instead of WARN_ONCE would be much more verbose, so I
removed it instead.

>
>> > >> +/**
>> > >> + * suspend_blocker_init() - Initialize a suspend blocker
>> > >> + * @blocker: The suspend blocker to initialize.
>> > >> + * @name:    The name of the suspend blocker to show in
>> > >> + *           /proc/suspend_blockers
>> > >
>> > > I don't think suspend_blockers should go to /proc. They are not process-related.
>> >
>> > I moved that comment to the stats patch. It is still in procfs though,
>> > as it is most similar to other procfs entries. It is not allowed under
>> > the sysfs rules, and we do not want to enable debugfs on a production
>> > system since it exposes some unsafe interfaces.
>>
>> You have to sort this out somehow. It does not belong to /proc.
>
> Agreed.

OK. I moved it to debugfs.

-- 
Arve Hjønnevåg

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Rafael J. Wysocki]

On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
> Adds ioctls to create a suspend_blocker, and to block and unblock suspend.
> To delete the suspend_blocker, close the device.

The changelog is minimalistic, so to speak.

Can you please describe the idea in more detail in it?

Also, perhaps you could use write() to initialize the suspend blocker?
I don't know really, it's just a thought.

You might not need ioctls() at all if you used write() like
write(name) -> initialize
write(1) -> activate
write(0) -> deactivate
write(1) -> activate
write(0) -> deactivate
etc.
read() -> check status (0 -> inactive, 1 -> active)
or something like this.

It might be extended for timeouts too. ;-)

> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ---
>  Documentation/power/suspend-blockers.txt |   17 ++++
>  include/linux/suspend_block_dev.h        |   25 ++++++
>  kernel/power/Kconfig                     |    9 ++
>  kernel/power/Makefile                    |    1 +
>  kernel/power/user_suspend_block.c        |  125 ++++++++++++++++++++++++++++++
>  5 files changed, 177 insertions(+), 0 deletions(-)
>  create mode 100644 include/linux/suspend_block_dev.h
>  create mode 100644 kernel/power/user_suspend_block.c
> 
> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
> index 743b870..35bc713 100644
> --- a/Documentation/power/suspend-blockers.txt
> +++ b/Documentation/power/suspend-blockers.txt
> @@ -74,3 +74,20 @@ if (list_empty(&state->pending_work))
>  else
>  	suspend_block(&state->suspend_blocker);
>  
> +User-space API
> +==============
> +
> +To create a suspend_blocker from user-space, open the suspend_blocker device:
> +    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
> +then call:
> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_INIT(strlen(name)), name);
> +
> +To activate a suspend_blocker call:
> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
> +
> +To unblock call:
> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
> +
> +To destroy the suspend_blocker, close the device:
> +    close(fd);
> +
> diff --git a/include/linux/suspend_block_dev.h b/include/linux/suspend_block_dev.h
> new file mode 100644
> index 0000000..a7c0bf9
> --- /dev/null
> +++ b/include/linux/suspend_block_dev.h
> @@ -0,0 +1,25 @@
> +/* include/linux/suspend_block_dev.h
> + *
> + * Copyright (C) 2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef _LINUX_SUSPEND_BLOCK_DEV_H
> +#define _LINUX_SUSPEND_BLOCK_DEV_H
> +
> +#include <linux/ioctl.h>
> +
> +#define SUSPEND_BLOCKER_IOCTL_INIT(len)		_IOC(_IOC_WRITE, 's', 0, len)
> +#define SUSPEND_BLOCKER_IOCTL_BLOCK		_IO('s', 1)
> +#define SUSPEND_BLOCKER_IOCTL_UNBLOCK		_IO('s', 3)
> +
> +#endif
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 9d1df13..2cf4c4d 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -126,6 +126,15 @@ config SUSPEND_BLOCK
>  	  /sys/power/request_state, the requested sleep state will be entered
>  	  when no suspend_blockers are active.
>  
> +config USER_SUSPEND_BLOCK
> +	bool "Userspace suspend blockers"
> +	depends on SUSPEND_BLOCK
> +	default y
> +	---help---
> +	  User-space suspend block api. Creates a misc device with ioctls
> +	  to create, block and unblock a suspend_blocker. The suspend_blocker
> +	  will be deleted when the device is closed.
> +
>  config HIBERNATION
>  	bool "Hibernation (aka 'suspend to disk')"
>  	depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
> index 29cdc9e..5c524f1 100644
> --- a/kernel/power/Makefile
> +++ b/kernel/power/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_PM)		+= main.o
>  obj-$(CONFIG_PM_SLEEP)		+= console.o
>  obj-$(CONFIG_FREEZER)		+= process.o
>  obj-$(CONFIG_SUSPEND_BLOCK)	+= suspend_block.o
> +obj-$(CONFIG_USER_SUSPEND_BLOCK)	+= user_suspend_block.o
>  obj-$(CONFIG_HIBERNATION)	+= swsusp.o disk.o snapshot.o swap.o user.o
>  
>  obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
> diff --git a/kernel/power/user_suspend_block.c b/kernel/power/user_suspend_block.c
> new file mode 100644
> index 0000000..782407c
> --- /dev/null
> +++ b/kernel/power/user_suspend_block.c
> @@ -0,0 +1,125 @@
> +/* kernel/power/user_suspend_block.c
> + *
> + * Copyright (C) 2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/suspend_block.h>
> +#include <linux/suspend_block_dev.h>
> +
> +enum {
> +	DEBUG_FAILURE	= BIT(0),
> +};
> +static int debug_mask = DEBUG_FAILURE;
> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +static DEFINE_MUTEX(ioctl_lock);
> +
> +struct user_suspend_blocker {
> +	struct suspend_blocker	blocker;
> +	char			name[0];
> +};
> +
> +static int create_user_suspend_blocker(struct file *file, void __user *name,
> +				 size_t name_len)
> +{
> +	struct user_suspend_blocker *bl;
> +	if (file->private_data)
> +		return -EBUSY;
> +	bl = kzalloc(sizeof(*bl) + name_len + 1, GFP_KERNEL);
> +	if (!bl)
> +		return -ENOMEM;
> +	if (copy_from_user(bl->name, name, name_len))
> +		goto err_fault;
> +	suspend_blocker_init(&bl->blocker, bl->name);
> +	file->private_data = bl;
> +	return 0;
> +
> +err_fault:
> +	kfree(bl);
> +	return -EFAULT;
> +}
> +
> +static long user_suspend_blocker_ioctl(struct file *file, unsigned int cmd,
> +				unsigned long _arg)
> +{
> +	void __user *arg = (void __user *)_arg;
> +	struct user_suspend_blocker *bl;
> +	long ret;
> +
> +	mutex_lock(&ioctl_lock);
> +	if ((cmd & ~IOCSIZE_MASK) == SUSPEND_BLOCKER_IOCTL_INIT(0)) {
> +		ret = create_user_suspend_blocker(file, arg, _IOC_SIZE(cmd));
> +		goto done;
> +	}
> +	bl = file->private_data;
> +	if (!bl) {
> +		ret = -ENOENT;
> +		goto done;
> +	}
> +	switch (cmd) {
> +	case SUSPEND_BLOCKER_IOCTL_BLOCK:
> +		suspend_block(&bl->blocker);
> +		ret = 0;
> +		break;
> +	case SUSPEND_BLOCKER_IOCTL_UNBLOCK:
> +		suspend_unblock(&bl->blocker);
> +		ret = 0;
> +		break;
> +	default:
> +		ret = -ENOTSUPP;
> +	}
> +done:
> +	if (ret && debug_mask & DEBUG_FAILURE)
> +		pr_err("user_suspend_blocker_ioctl: cmd %x failed, %ld\n",
> +			cmd, ret);
> +	mutex_unlock(&ioctl_lock);
> +	return ret;
> +}
> +
> +static int user_suspend_blocker_release(struct inode *inode, struct file *file)
> +{
> +	struct user_suspend_blocker *bl = file->private_data;
> +	if (!bl)
> +		return 0;
> +	suspend_blocker_destroy(&bl->blocker);
> +	kfree(bl);
> +	return 0;
> +}
> +
> +const struct file_operations user_suspend_blocker_fops = {
> +	.release = user_suspend_blocker_release,
> +	.unlocked_ioctl = user_suspend_blocker_ioctl,
> +};
> +
> +struct miscdevice user_suspend_blocker_device = {
> +	.minor = MISC_DYNAMIC_MINOR,
> +	.name = "suspend_blocker",
> +	.fops = &user_suspend_blocker_fops,
> +};
> +
> +static int __init user_suspend_blocker_init(void)
> +{
> +	return misc_register(&user_suspend_blocker_device);
> +}
> +
> +static void __exit user_suspend_blocker_exit(void)
> +{
> +	misc_deregister(&user_suspend_blocker_device);
> +}
> +
> +module_init(user_suspend_blocker_init);
> +module_exit(user_suspend_blocker_exit);


-- 
Everyone knows that debugging is twice as hard as writing a program
in the first place.  So if you're as clever as you can be when you write it,
how will you ever debug it? --- Brian Kernighan
_______________________________________________
linux-pm mailing list
linux-pm@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/linux-pm

Re: [PATCH 3/8] PM: suspend_block: Abort task freezing if a suspend_blocker is active.

[Rafael J. Wysocki]

On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
> If a suspend_blocker is active, suspend will fail anyway. Since
> try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
> as soon as someone blocks suspend (e.g. from an interrupt handler) improves
> the worst case wakeup latency.
> 
> On an older kernel where task freezing could fail for processes attached
> to a debugger, this fixed a problem where the device sometimes hung for
> 20 seconds before the screen turned on.
> 
> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ---
>  kernel/power/process.c |   23 ++++++++++++++++++-----
>  1 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index ca63401..76d7cdb 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -13,6 +13,7 @@
>  #include <linux/module.h>
>  #include <linux/syscalls.h>
>  #include <linux/freezer.h>
> +#include <linux/suspend_block.h>
>  
>  /* 
>   * Timeout for stopping processes
> @@ -36,6 +37,7 @@ static int try_to_freeze_tasks(bool sig_only)
>  	struct timeval start, end;
>  	u64 elapsed_csecs64;
>  	unsigned int elapsed_csecs;
> +	unsigned int wakeup = 0;

Make it a bool, please.

>  	do_gettimeofday(&start);
>  
> @@ -62,6 +64,10 @@ static int try_to_freeze_tasks(bool sig_only)
>  		} while_each_thread(g, p);
>  		read_unlock(&tasklist_lock);
>  		yield();			/* Yield is okay here */
> +		if (todo && suspend_is_blocked()) {
> +			wakeup = 1;

'true', please.

> +			break;
> +		}
>  		if (time_after(jiffies, end_time))
>  			break;
>  	} while (todo);
> @@ -77,11 +83,18 @@ static int try_to_freeze_tasks(bool sig_only)
>  		 * and caller must call thaw_processes() if something fails),
>  		 * but it cleans up leftover PF_FREEZE requests.
>  		 */
> -		printk("\n");
> -		printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
> -				"(%d tasks refusing to freeze):\n",
> -				elapsed_csecs / 100, elapsed_csecs % 100, todo);
> -		show_state();
> +		if (wakeup) {
> +			printk("\n");

Why is the separate printk() necessary ?

> +			printk(KERN_ERR "Freezing of %s aborted\n",
> +					sig_only ? "user space " : "tasks ");
> +		} else {
> +			printk("\n");

Why is the separate printk() necessary ?

> +			printk(KERN_ERR
> +			       "Freezing of tasks failed after %d.%02d seconds "
> +			       "(%d tasks refusing to freeze):\n",
> +			       elapsed_csecs / 100, elapsed_csecs % 100, todo);
> +			show_state();
> +		}
>  		read_lock(&tasklist_lock);
>  		do_each_thread(g, p) {
>  			task_lock(p);


-- 
Everyone knows that debugging is twice as hard as writing a program
in the first place.  So if you're as clever as you can be when you write it,
how will you ever debug it? --- Brian Kernighan
_______________________________________________
linux-pm mailing list
linux-pm@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/linux-pm

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2009/4/29 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
>> diff --git a/Documentation/power/suspend-blockers.txt b/Documentation/power/suspend-blockers.txt
>> new file mode 100644
>> index 0000000..743b870
>> --- /dev/null
>> +++ b/Documentation/power/suspend-blockers.txt
>> @@ -0,0 +1,76 @@
>> +Suspend blockers
>> +================
>> +
>> +A suspend_blocker prevents the system from entering suspend.
>
> I'd say "suspend blocker", without the underscore.
>
> Also, I'd try to provide a general explanation of how this is supposed to
> work here, as an introduction.  Something like:
>
> "Suspend blockers provide a mechanism allowing device drivers and user
> space processes to prevent the system from entering a sleep state, such as
> the ACPI S3 state.
>
> To use a suspend blocker, a device driver needs a struct suspend_blocker object
> that has to be initialized with the help of suspend_blocker_init().  When no
> longer needed, the suspend blocker must be garbage collected with the help
> of suspend_blocker_destroy().
>
> A suspend blocker is activated using suspend_block(), which prevents the
> system from entering any sleep state until the suspend blocker is deactivated
> with suspend_unblock().  Many suspend blockers may be used simultaneously
> and the system is prevented from entering sleep states as long as at least one
> of them is active."
>

I added most of this, see new text below.

> BTW, I don't really like the names "suspend_block" and "suspend_unblock".
> See below for possible alternatives.
>
>> +If the suspend operation has already started when calling suspend_block on a
>> +suspend_blocker, it will abort the suspend operation as long it has not already
>> +reached the sysdev suspend stage. This means that calling suspend_block from an
>> +interrupt handler or a freezeable thread always works, but if you call
>> +block_suspend
>
> Surely suspend_block() ?

Yes.

>
>> from a sysdev suspend handler you must also return an error from
>> +that handler to abort suspend.
>
> Well, if a sysdev suspend handler returns an error code, suspend will be
> aborted anyway, so I'm not sure what the point in using suspend blockers from
> sysdev suspend handlers really is.  Perhaps it's better to say "don't use
> suspend blockers from withing sysdev suspend handlers"?

You still need the suspend blocker to prevent the system from trying
to enter suspend again. I changed the text to "to abort a suspend
sequence that was already started".

>
>> +
>
> I'd say "For example" here.
>
>> +Suspend blockers can be used to allow user-space to decide which keys should
>> +wake the full system up and turn the screen on. Use set_irq_wake or a platform
>> +specific api to make sure the keypad interrupt wakes up the cpu. Once the keypad
>> +driver has resumed, the sequence of events can look like this:
>> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
>> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
>> +- The keypad-scan code detects a key change and reports it to the input-event
>> +  driver.
>> +- The input-event driver sees the key change, enqueues an event, and calls
>> +  suspend_block on the input-event-queue suspend_blocker.
>> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
>> +  on the keypad-scan suspend_blocker.
>> +- The user-space input-event thread returns from select/poll, calls
>> +  suspend_block on the process-input-events suspend_blocker and then calls read
>> +  on the input-event device.
>> +- The input-event driver dequeues the key-event and, since the queue is now
>> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
>> +- The user-space input-event thread returns from read. It determines that the
>> +  key should not wake up the full system, calls suspend_unblock on the
>> +  process-input-events suspend_blocker and calls select or poll.
>> +
>> +                 Key pressed   Key released
>> +                     |             |
>> +keypad-scan          ++++++++++++++++++
>> +input-event-queue        +++          +++
>> +process-input-events       +++          +++
>> +
>> +
>> +Driver API
>> +==========
>> +
>> +A driver can use the suspend block api by adding a suspend_blocker variable to
>> +its state and calling suspend_blocker_init. For instance:
>> +struct state {
>> +     struct suspend_blocker suspend_blocker;
>> +}
>> +
>> +init() {
>> +     suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
>> +}
>> +
>> +Before freeing the memory, suspend_blocker_destroy must be called:
>> +
>> +uninit() {
>> +     suspend_blocker_destroy(&state->suspend_blocker);
>> +}
>> +
>> +When the driver determines that it needs to run (usually in an interrupt
>> +handler) it calls suspend_block:
>> +     suspend_block(&state->suspend_blocker);
>
> suspend_blocker_activate() ?
> suspend_blocker_enable() ?
> suspend_blocker_start() ?
>

I don't like any of those better than suspend_block, but if there is
some agreement on what it should be changed to, I'll change it.

>> +
>> +When it no longer needs to run it calls suspend_unblock:
>> +     suspend_unblock(&state->suspend_blocker);
>
> suspend_blocker_deactivate() ?
> suspend_blocker_disable() ?
> suspend_blocker_finish() ?
>
>> +
>> +Calling suspend_block when the suspend blocker is active or suspend_unblock when
>> +it is not active has no effect. This allows drivers to update their state and
>> +call suspend suspend_block or suspend_unblock based on the result.
>> +For instance:
>> +
>> +if (list_empty(&state->pending_work))
>> +     suspend_unblock(&state->suspend_blocker);
>> +else
>> +     suspend_block(&state->suspend_blocker);
>> +


-- 
Arve Hjønnevåg


----

Suspend blockers
================

Suspend blockers provide a mechanism for device drivers and user-space processes
to prevent the system from entering suspend. Only suspend states requested
through /sys/power/request_state are prevented. Writing to /sys/power/state
will ignore suspend blockers, and sleep states entered from idle are unaffected.

To use a suspend blocker, a device driver needs a struct suspend_blocker object
that has to be initialized with suspend_blocker_init. When no longer needed,
the suspend blocker must be destroyed with suspend_blocker_destroy.

A suspend blocker is activated using suspend_block, which prevents the system
from entering suspend until the suspend blocker is deactivated with
suspend_unblock. Many suspend blockers may be used simultaneously, and the
system is prevented from entering suspend as long as at least one of them is
active.

If the suspend operation has already started when calling suspend_block on a
suspend_blocker, it will abort the suspend operation as long it has not already
reached the sysdev suspend stage. This means that calling suspend_block from an
interrupt handler or a freezeable thread always works, but if you call
suspend_block from a sysdev suspend handler you must also return an error from
that handler to abort a suspend sequence that was already started.

In cell phones or other embedded systems where powering the screen is a
significant drain on the battery, suspend blockers can be used to allow
user-space to decide whether a keystroke received while the system is suspended
should cause the screen to be turned back on or allow the system to go back into
suspend. Use set_irq_wake or a platform specific api to make sure the keypad
interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
events can look like this:

- The Keypad driver gets an interrupt. It then calls suspend_block on the
  keypad-scan suspend_blocker and starts scanning the keypad matrix.
- The keypad-scan code detects a key change and reports it to the input-event
  driver.
- The input-event driver sees the key change, enqueues an event, and calls
  suspend_block on the input-event-queue suspend_blocker.
- The keypad-scan code detects that no keys are held and calls suspend_unblock
  on the keypad-scan suspend_blocker.
- The user-space input-event thread returns from select/poll, calls
  suspend_block on the process-input-events suspend_blocker and then calls read
  on the input-event device.
- The input-event driver dequeues the key-event and, since the queue is now
  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
- The user-space input-event thread returns from read. If it determines that
  the key should leave the screen off, it calls suspend_unblock on the
  process_input_events suspend_blocker and then calls select or poll. The
  system will automatically suspend again, since now no suspend blockers are
  active.

                 Key pressed   Key released
                     |             |
keypad-scan          ++++++++++++++++++
input-event-queue        +++          +++
process-input-events       +++          +++


Driver API
==========

A driver can use the suspend block api by adding a suspend_blocker variable to
its state and calling suspend_blocker_init. For instance:
struct state {
        struct suspend_blocker suspend_blocker;
}

init() {
        suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
}

Before freeing the memory, suspend_blocker_destroy must be called:

uninit() {
        suspend_blocker_destroy(&state->suspend_blocker);
}

When the driver determines that it needs to run (usually in an interrupt
handler) it calls suspend_block:
        suspend_block(&state->suspend_blocker);

When it no longer needs to run it calls suspend_unblock:
        suspend_unblock(&state->suspend_blocker);

Calling suspend_block when the suspend blocker is active or suspend_unblock when
it is not active has no effect. This allows drivers to update their state and
call suspend suspend_block or suspend_unblock based on the result.
For instance:

if (list_empty(&state->pending_work))
        suspend_unblock(&state->suspend_blocker);
else
        suspend_block(&state->suspend_blocker);

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2009/4/29 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
>> diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
>> new file mode 100755
>> index 0000000..7820c60
>> --- /dev/null
>> +++ b/include/linux/suspend_block.h
>
> suspend_blockers.h perhaps?

suspend_blocker.h?

>
>> @@ -0,0 +1,61 @@
>> +/* include/linux/suspend_block.h
>> + *
>> + * Copyright (C) 2007-2009 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + */
>> +
>> +#ifndef _LINUX_SUSPEND_BLOCK_H
>> +#define _LINUX_SUSPEND_BLOCK_H
>
> SUSPEND_BLOCKERS_H ?
>
>> +
>> +/* A suspend_blocker prevents the system from entering suspend when active.
>> + */
>> +
>> +struct suspend_blocker {
>> +#ifdef CONFIG_SUSPEND_BLOCK
>
> CONFIG_SUSPEND_BLOCKERS ?

OK.

>
>> +     atomic_t            flags;
>> +     const char         *name;
>> +#endif
>> +};
>> +
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +
>> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
>> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
>> +void suspend_block(struct suspend_blocker *blocker);
>> +void suspend_unblock(struct suspend_blocker *blocker);
>> +
>> +/* is_blocking_suspend returns true if the suspend_blocker is currently active.
>> + */
>> +bool is_blocking_suspend(struct suspend_blocker *blocker);
>
> suspend_blocker_is_active() ?
OK.
> suspend_blocker_enabled() ?
>
>> +
>> +/* suspend_is_blocked can be used by generic power management code to abort
>> + * suspend.
>> + *
>> + * To preserve backward compatibility suspend_is_blocked returns 0 unless it
>> + * is called during suspend initiated from the suspend_block code.
>> + */
>> +bool suspend_is_blocked(void);
>> +
>> +#else
>> +
>> +static inline void suspend_blocker_init(struct suspend_blocker *blocker,
>> +                                     const char *name) {}
>> +static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
>> +static inline void suspend_block(struct suspend_blocker *blocker) {}
>> +static inline void suspend_unblock(struct suspend_blocker *blocker) {}
>> +static inline bool is_blocking_suspend(struct suspend_blocker *bl) { return 0; }
>> +static inline bool suspend_is_blocked(void) { return 0; }
>> +
>> +#endif
>> +
>> +#endif
>> +
>> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
>> index 23bd4da..9d1df13 100644
>> --- a/kernel/power/Kconfig
>> +++ b/kernel/power/Kconfig
>> @@ -116,6 +116,16 @@ config SUSPEND_FREEZER
>>
>>         Turning OFF this setting is NOT recommended! If in doubt, say Y.
>>
>> +config SUSPEND_BLOCK
>> +     bool "Suspend block"
>> +     depends on PM
>> +     select RTC_LIB
>
> depends on RTC_LIB
>
> select doesn't really work and I don't think it ever will.

Nothing depends on RTC_LIB, it is only selected.

>
>> +     default n
>> +     ---help---
>> +       Enable suspend_block.
>
> Enable suspend blockers.

OK.

>
>> When user space requests a sleep state through
>> +       /sys/power/request_state, the requested sleep state will be entered
>> +       when no suspend_blockers are active.
>
> Well, if you don't want suspend blockers to block suspend started via
> /sys/power/state, it's worth making it crystal clear in the documentation too.

I added this to the intro.

>
>> +
>>  config HIBERNATION
>>       bool "Hibernation (aka 'suspend to disk')"
>>       depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
>> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
>> index 720ea4f..29cdc9e 100644
>> --- a/kernel/power/Makefile
>> +++ b/kernel/power/Makefile
>> @@ -6,6 +6,7 @@ endif
>>  obj-$(CONFIG_PM)             += main.o
>>  obj-$(CONFIG_PM_SLEEP)               += console.o
>>  obj-$(CONFIG_FREEZER)                += process.o
>> +obj-$(CONFIG_SUSPEND_BLOCK)  += suspend_block.o
>>  obj-$(CONFIG_HIBERNATION)    += swsusp.o disk.o snapshot.o swap.o user.o
>>
>>  obj-$(CONFIG_MAGIC_SYSRQ)    += poweroff.o
>> diff --git a/kernel/power/main.c b/kernel/power/main.c
>> index c9632f8..e4c6b20 100644
>> --- a/kernel/power/main.c
>> +++ b/kernel/power/main.c
>> @@ -22,6 +22,7 @@
>>  #include <linux/freezer.h>
>>  #include <linux/vmstat.h>
>>  #include <linux/syscalls.h>
>> +#include <linux/suspend_block.h>
>>
>>  #include "power.h"
>>
>> @@ -392,6 +393,9 @@ static void suspend_finish(void)
>>
>>
>>  static const char * const pm_states[PM_SUSPEND_MAX] = {
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +     [PM_SUSPEND_ON]         = "on",
>> +#endif
>
> Why #ifdef?

Removed.

>
>>       [PM_SUSPEND_STANDBY]    = "standby",
>>       [PM_SUSPEND_MEM]        = "mem",
>>  };
>> @@ -540,6 +544,61 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>>
>>  power_attr(state);
>>
>> +/**
>> + *   request_state - control system power state.
>> + *
>> + *   This is similar to state, but it does not block until the system
>> + *   resumes, and it will try to re-enter the state until another state is
>> + *   requested. Suspend blockers are respected and the requested state will
>> + *   only be entered when no suspend blockers are active.
>> + *   Write "on" to cancel.
>> + */
>> +
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +static ssize_t request_state_show(struct kobject *kobj,
>> +                               struct kobj_attribute *attr, char *buf)
>> +{
>> +     char *s = buf;
>> +     int i;
>> +
>> +     for (i = 0; i < PM_SUSPEND_MAX; i++) {
>> +             if (pm_states[i] && (i == PM_SUSPEND_ON || valid_state(i)))
>> +                     s += sprintf(s, "%s ", pm_states[i]);
>> +     }
>> +     if (s != buf)
>> +             /* convert the last space to a newline */
>> +             *(s-1) = '\n';
>> +     return (s - buf);
>> +}
>> +
>> +static ssize_t request_state_store(struct kobject *kobj,
>> +                                struct kobj_attribute *attr,
>> +                                const char *buf, size_t n)
>> +{
>> +     suspend_state_t state = PM_SUSPEND_ON;
>> +     const char * const *s;
>> +     char *p;
>> +     int len;
>> +     int error = -EINVAL;
>> +
>> +     p = memchr(buf, '\n', n);
>> +     len = p ? p - buf : n;
>> +
>> +     for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
>> +             if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
>> +                     break;
>> +     }
>> +     if (state < PM_SUSPEND_MAX && *s)
>> +             if (state == PM_SUSPEND_ON || valid_state(state)) {
>> +                     error = 0;
>> +                     request_suspend_state(state);
>> +             }
>> +     return error ? error : n;
>> +}
>> +
>> +power_attr(request_state);
>> +#endif /* CONFIG_SUSPEND_BLOCK */
>> +
>>  #ifdef CONFIG_PM_TRACE
>>  int pm_trace_enabled;
>>
>> @@ -567,6 +626,9 @@ power_attr(pm_trace);
>>
>>  static struct attribute * g[] = {
>>       &state_attr.attr,
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +     &request_state_attr.attr,
>> +#endif
>>  #ifdef CONFIG_PM_TRACE
>>       &pm_trace_attr.attr,
>>  #endif
>> diff --git a/kernel/power/power.h b/kernel/power/power.h
>> index 46b5ec7..2414a74 100644
>> --- a/kernel/power/power.h
>> +++ b/kernel/power/power.h
>> @@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
>>  {
>>  }
>>  #endif
>> +
>> +#ifdef CONFIG_SUSPEND_BLOCK
>> +/* kernel/power/suspend_block.c */
>> +void request_suspend_state(suspend_state_t state);
>> +#endif
>
> Is the #ifdef really necessary?
>

No, but it gives a compile error instead of a link error if you call
request_suspend_state when it is not available so it is useful.

>> +
>> diff --git a/kernel/power/suspend_block.c b/kernel/power/suspend_block.c
>> new file mode 100644
>> index 0000000..b4f2191
>> --- /dev/null
>> +++ b/kernel/power/suspend_block.c
>> @@ -0,0 +1,257 @@
>> +/* kernel/power/suspend_block.c
>> + *
>> + * Copyright (C) 2005-2008 Google, Inc.
>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/rtc.h>
>> +#include <linux/suspend.h>
>> +#include <linux/suspend_block.h>
>> +#include <linux/sysdev.h>
>> +#include "power.h"
>> +
>> +enum {
>> +     DEBUG_EXIT_SUSPEND = 1U << 0,
>> +     DEBUG_WAKEUP = 1U << 1,
>> +     DEBUG_USER_STATE = 1U << 2,
>> +     DEBUG_SUSPEND = 1U << 3,
>> +     DEBUG_SUSPEND_BLOCKER = 1U << 4,
>> +};
>> +static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
>> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
>> +
>> +#define SB_INITIALIZED            (1U << 8)
>> +#define SB_ACTIVE                 (1U << 9)
>> +
>> +static DEFINE_SPINLOCK(state_lock);
>> +static atomic_t suspend_block_count;
>> +static atomic_t current_event_num;
>> +struct workqueue_struct *suspend_work_queue;
>> +struct suspend_blocker main_suspend_blocker;
>> +static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
>> +static bool enable_suspend_blockers;
>> +
>> +bool suspend_is_blocked(void)
>> +{
>> +     if (WARN_ONCE(!enable_suspend_blockers, "ignoring suspend blockers\n"))
>> +             return 0;
>> +     return !!atomic_read(&suspend_block_count);
>> +}
>> +
>> +static void suspend_worker(struct work_struct *work)
>> +{
>> +     int ret;
>> +     int entry_event_num;
>> +
>> +     enable_suspend_blockers = 1;
>
> 'true' instead of '1', please.

OK.

>
>> +
>> +retry:
>> +     if (suspend_is_blocked()) {
>> +             if (debug_mask & DEBUG_SUSPEND)
>> +                     pr_info("suspend: abort suspend\n");
>> +             goto abort;
>
> If that were in a loop you could just use 'break' here.

do you think this is better:
while(1) {
        if (exception1) {
                ...
                break;
        }
        ...
        if (exception2) {
                ...
                continue;
        }
        break;
}
>
>> +     }
>> +
>> +     entry_event_num = atomic_read(&current_event_num);
>> +     if (debug_mask & DEBUG_SUSPEND)
>> +             pr_info("suspend: enter suspend\n");
>> +     ret = pm_suspend(requested_suspend_state);
>> +     if (debug_mask & DEBUG_EXIT_SUSPEND) {
>> +             struct timespec ts;
>> +             struct rtc_time tm;
>> +             getnstimeofday(&ts);
>> +             rtc_time_to_tm(ts.tv_sec, &tm);
>> +             pr_info("suspend: exit suspend, ret = %d "
>> +                     "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n", ret,
>> +                     tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
>> +                     tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
>> +     }
>> +     if (atomic_read(&current_event_num) == entry_event_num) {
>> +             if (debug_mask & DEBUG_SUSPEND)
>> +                     pr_info("suspend: pm_suspend returned with no event\n");
>> +             goto retry;
>
> Put that into a loop and use 'continue' here?  Or use 'break' to go out of
> the loop?

The retry is a workaround for the lack of suspend_block_timeout.

>
>> +     }
>> +abort:
>> +     enable_suspend_blockers = 0;
>
> 'false' instead of '0', please.

OK.

>
>> +}
>> +static DECLARE_WORK(suspend_work, suspend_worker);
>> +
>> +static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
>> +{
>> +     int ret = suspend_is_blocked() ? -EAGAIN : 0;
>> +     if (debug_mask & DEBUG_SUSPEND)
>> +             pr_info("suspend_block_suspend return %d\n", ret);
>> +     return ret;
>> +}
>> +
>> +static struct sysdev_class suspend_block_sysclass = {
>> +     .name = "suspend_block",
>> +     .suspend = suspend_block_suspend,
>> +};
>> +static struct sys_device suspend_block_sysdev = {
>> +     .cls = &suspend_block_sysclass,
>> +};
>> +
>
> Hmm.  Perhaps add the suspend_is_blocked() check at the beginning of
> sysdev_suspend() instead of this?  Surely you don't want to suspend
> any sysdevs with any suspend blockers active, right?

You could make the same argument for any device. Using a sysdev makes
the patch easier to apply.

>
>> +/**
>> + * suspend_blocker_init() - Initialize a suspend blocker
>> + * @blocker: The suspend blocker to initialize.
>> + * @name:    The name of the suspend blocker to show in
>> + *           /proc/suspend_blockers
>> + */
>> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
>> +{
>> +     if (name)
>> +             blocker->name = name;
>> +     BUG_ON(!blocker->name);
>
> Do you really want to crash the kernel in this case?  WARN_ON() might be better IMO.

OK.

>
> Also, this assumes that the caller won't release the memory used to store the
> 'name' string.  it might be a good idea to point that out in the kerneldoc
> comment.
>
>> +
>> +     if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> +             pr_info("suspend_blocker_init name=%s\n", blocker->name);
>> +
>> +     atomic_set(&blocker->flags, SB_INITIALIZED);
>> +}
>> +EXPORT_SYMBOL(suspend_blocker_init);
>> +
>> +/**
>> + * suspend_blocker_destroy() - Destroy a suspend blocker
>> + * @blocker: The suspend blocker to destroy.
>> + */
>> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
>> +{
>> +     int flags;
>> +     if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> +             pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
>> +     flags = atomic_xchg(&blocker->flags, 0);
>> +     WARN(!(flags & SB_INITIALIZED), "suspend_blocker_destroy called on "
>> +                                     "uninitialized suspend_blocker\n");
>> +     if (flags == (SB_INITIALIZED | SB_ACTIVE))
>> +             if (atomic_dec_and_test(&suspend_block_count))
>> +                     queue_work(suspend_work_queue, &suspend_work);
>> +}
>> +EXPORT_SYMBOL(suspend_blocker_destroy);
>> +
>> +/**
>> + * suspend_block() - Block suspend
>> + * @blocker: The suspend blocker to use
>> + */
>> +void suspend_block(struct suspend_blocker *blocker)
>> +{
>> +     BUG_ON(!(atomic_read(&blocker->flags) & SB_INITIALIZED));
>
> WARN_ON() and exit instead?  BUG_ON() is a bit drastic IMHO.
>
>> +
>> +     if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> +             pr_info("suspend_block: %s\n", blocker->name);
>> +     if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED,
>> +         SB_INITIALIZED | SB_ACTIVE) == SB_INITIALIZED)
>> +             atomic_inc(&suspend_block_count);
>> +
>> +     atomic_inc(&current_event_num);
>> +}
>> +EXPORT_SYMBOL(suspend_block);
>> +
>> +/**
>> + * suspend_unblock() - Unblock suspend
>> + * @blocker: The suspend blocker to unblock.
>> + *
>> + * If no other suspend blockers block suspend, the system will suspend.
>> + */
>> +void suspend_unblock(struct suspend_blocker *blocker)
>> +{
>> +     if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> +             pr_info("suspend_unblock: %s\n", blocker->name);
>> +
>> +     if (atomic_cmpxchg(&blocker->flags, SB_INITIALIZED | SB_ACTIVE,
>> +         SB_INITIALIZED) == (SB_INITIALIZED | SB_ACTIVE))
>> +             if (atomic_dec_and_test(&suspend_block_count))
>> +                     queue_work(suspend_work_queue, &suspend_work);
>> +}
>> +EXPORT_SYMBOL(suspend_unblock);
>> +
>> +/**
>> + * is_blocking_suspend() - Test if a suspend blocker is blocking suspend
>> + * @blocker: The suspend blocker to check.
>> + */
>> +bool is_blocking_suspend(struct suspend_blocker *blocker)
>> +{
>> +     return !!(atomic_read(&blocker->flags) & SB_ACTIVE);
>
> Check SB_INITIALIZED too, perhaps?  WARN_ON(!SB_INITIALIZED)?

Added WARN_ON.

>
>> +}
>> +EXPORT_SYMBOL(is_blocking_suspend);
>> +
>> +void request_suspend_state(suspend_state_t state)
>> +{
>> +     unsigned long irqflags;
>> +     spin_lock_irqsave(&state_lock, irqflags);
>> +     if (debug_mask & DEBUG_USER_STATE) {
>> +             struct timespec ts;
>> +             struct rtc_time tm;
>> +             getnstimeofday(&ts);
>> +             rtc_time_to_tm(ts.tv_sec, &tm);
>> +             pr_info("request_suspend_state: %s (%d->%d) at %lld "
>> +                     "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n",
>> +                     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
>> +                     requested_suspend_state, state,
>> +                     ktime_to_ns(ktime_get()),
>> +                     tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
>> +                     tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec);
>> +     }
>> +     requested_suspend_state = state;
>> +     if (state == PM_SUSPEND_ON)
>> +             suspend_block(&main_suspend_blocker);
>> +     else
>> +             suspend_unblock(&main_suspend_blocker);
>> +     spin_unlock_irqrestore(&state_lock, irqflags);
>> +}
>> +
>> +static int __init suspend_block_init(void)
>> +{
>> +     int ret;
>> +
>> +     suspend_blocker_init(&main_suspend_blocker, "main");
>> +     suspend_block(&main_suspend_blocker);
>> +
>> +     ret = sysdev_class_register(&suspend_block_sysclass);
>> +     if (ret) {
>> +             pr_err("suspend_block_init: sysdev_class_register failed\n");
>> +             goto err_sysdev_class_register;
>> +     }
>> +     ret = sysdev_register(&suspend_block_sysdev);
>> +     if (ret) {
>> +             pr_err("suspend_block_init: suspend_block_sysdev failed\n");
>> +             goto err_sysdev_register;
>> +     }
>> +
>> +     suspend_work_queue = create_singlethread_workqueue("suspend");
>
> Do we need a separate workqueue for this purpose?
>

Yes. Some drivers wait on work that runs on the main workqueue in
their suspend handler.

>> +     if (suspend_work_queue == NULL) {
>> +             ret = -ENOMEM;
>> +             goto err_suspend_work_queue;
>> +     }
>> +
>> +     return 0;
>> +
>> +err_suspend_work_queue:
>> +     sysdev_unregister(&suspend_block_sysdev);
>> +err_sysdev_register:
>> +     sysdev_class_unregister(&suspend_block_sysclass);
>> +err_sysdev_class_register:
>> +     suspend_blocker_destroy(&main_suspend_blocker);
>> +     return ret;
>> +}
>> +
>> +static void  __exit suspend_block_exit(void)
>> +{
>> +     destroy_workqueue(suspend_work_queue);
>> +     sysdev_unregister(&suspend_block_sysdev);
>> +     sysdev_class_unregister(&suspend_block_sysclass);
>> +     suspend_blocker_destroy(&main_suspend_blocker);
>> +}
>> +
>> +core_initcall(suspend_block_init);
>> +module_exit(suspend_block_exit);
>
> Thanks,
> Rafael
>



-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Thursday 30 April 2009, Arve Hjønnevåg wrote:
> 2009/4/29 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Wednesday 15 April 2009, Arve Hjønnevåg wrote:
> >> diff --git a/include/linux/suspend_block.h b/include/linux/suspend_block.h
> >> new file mode 100755
> >> index 0000000..7820c60
> >> --- /dev/null
> >> +++ b/include/linux/suspend_block.h
> >
> > suspend_blockers.h perhaps?
> 
> suspend_blocker.h?

Fine by me.

[--snip--]
> >> +config SUSPEND_BLOCK
> >> +     bool "Suspend block"
> >> +     depends on PM
> >> +     select RTC_LIB
> >
> > depends on RTC_LIB
> >
> > select doesn't really work and I don't think it ever will.
> 
> Nothing depends on RTC_LIB, it is only selected.

If nothing in your code needs anything depending on RTC_LIB, why select it?

[--snip--]
> >
> >> +
> >> +retry:
> >> +     if (suspend_is_blocked()) {
> >> +             if (debug_mask & DEBUG_SUSPEND)
> >> +                     pr_info("suspend: abort suspend\n");
> >> +             goto abort;
> >
> > If that were in a loop you could just use 'break' here.
> 
> do you think this is better:
> while(1) {
>         if (exception1) {
>                 ...
>                 break;
>         }
>         ...
>         if (exception2) {
>                 ...
>                 continue;
>         }
>         break;
> }

I rather thought of

for (;;) {
         if (exception1) {
                 ...
                 break;
         }
         ...
         if (!exception2)
                 break;
         ...
}

[--snip--]
> >> +static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
> >> +{
> >> +     int ret = suspend_is_blocked() ? -EAGAIN : 0;
> >> +     if (debug_mask & DEBUG_SUSPEND)
> >> +             pr_info("suspend_block_suspend return %d\n", ret);
> >> +     return ret;
> >> +}
> >> +
> >> +static struct sysdev_class suspend_block_sysclass = {
> >> +     .name = "suspend_block",
> >> +     .suspend = suspend_block_suspend,
> >> +};
> >> +static struct sys_device suspend_block_sysdev = {
> >> +     .cls = &suspend_block_sysclass,
> >> +};
> >> +
> >
> > Hmm.  Perhaps add the suspend_is_blocked() check at the beginning of
> > sysdev_suspend() instead of this?  Surely you don't want to suspend
> > any sysdevs with any suspend blockers active, right?
> 
> You could make the same argument for any device. Using a sysdev makes
> the patch easier to apply.

You've lost me here. :-)

AFAICT, the only purpose of the sysdev class above is to abort suspend if
suspend_is_blocked() returns 'true'.  If that is correct, then IMO you could
achieve the same goal by calling suspend_is_blocked() directly from
sysdev_suspend(), right before check_wakeup_irqs().  Or am I missing anything?

Thanks,
Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Sunday 26 April 2009, Pavel Machek wrote:
> Hi!
> 
> > >> --- a/kernel/power/power.h
> > >> +++ b/kernel/power/power.h
> > >> @@ -223,3 +223,9 @@ static inline void suspend_thaw_processes(void)
> > >>  {
> > >>  }
> > >>  #endif
> > >> +
> > >> +#ifdef CONFIG_SUSPEND_BLOCK
> > >> +/* kernel/power/suspend_block.c */
> > >> +void request_suspend_state(suspend_state_t state);
> > >> +#endif
> > >
> > > Is the #ifdef really necessary?
> > >
> > 
> > No, but it gives a compile error instead of a link error if you call
> > request_suspend_state when it is not available so it is useful.
> 
> I believe #ifdef is too ugly and link error is really good enough.

Well, I agree with this FWIW.

We don't ususally use #ifdefs around function headers, unless they are defined
conditionally.

Thanks,
Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Pavel Machek]

Hi!

> > >> +config SUSPEND_BLOCK
> > >> +     bool "Suspend block"
> > >> +     depends on PM
> > >> +     select RTC_LIB
> > >
> > > depends on RTC_LIB
> > >
> > > select doesn't really work and I don't think it ever will.
> > 
> > Nothing depends on RTC_LIB, it is only selected.
> 
> If nothing in your code needs anything depending on RTC_LIB, why select it?

He wants to say nothing in _kernel proper_ depends on RTC_LIB:

pavel@amd:/data/l/linux-good$ grep 'select RTC_LIB' `find . -name
"Kconfig"`
./arch/arm/Kconfig:	select RTC_LIB
./arch/mips/Kconfig:	select RTC_LIB
./drivers/rtc/Kconfig:	select RTC_LIB
pavel@amd:/data/l/linux-good$ grep 'depends.*RTC_LIB' `find . -name
"Kconfig"`
pavel@amd:/data/l/linux-good$ 

RTC_LIB seems to be designed for select.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2009/5/2 Rafael J. Wysocki <rjw@sisk.pl>:
> [--snip--]
>> >
>> >> +
>> >> +retry:
>> >> +     if (suspend_is_blocked()) {
>> >> +             if (debug_mask & DEBUG_SUSPEND)
>> >> +                     pr_info("suspend: abort suspend\n");
>> >> +             goto abort;
>> >
>> > If that were in a loop you could just use 'break' here.
>>
>> do you think this is better:
>> while(1) {
>>         if (exception1) {
>>                 ...
>>                 break;
>>         }
>>         ...
>>         if (exception2) {
>>                 ...
>>                 continue;
>>         }
>>         break;
>> }
>
> I rather thought of
>
> for (;;) {
>         if (exception1) {
>                 ...
>                 break;
>         }
>         ...
>         if (!exception2)
>                 break;
>         ...
> }

I don't think that is much better, but I changed the first patch to
use a loop anyway. The loop is then removed (as before) in the patch
that adds the stats.

>
> [--snip--]
>> >> +static int suspend_block_suspend(struct sys_device *dev, pm_message_t state)
>> >> +{
>> >> +     int ret = suspend_is_blocked() ? -EAGAIN : 0;
>> >> +     if (debug_mask & DEBUG_SUSPEND)
>> >> +             pr_info("suspend_block_suspend return %d\n", ret);
>> >> +     return ret;
>> >> +}
>> >> +
>> >> +static struct sysdev_class suspend_block_sysclass = {
>> >> +     .name = "suspend_block",
>> >> +     .suspend = suspend_block_suspend,
>> >> +};
>> >> +static struct sys_device suspend_block_sysdev = {
>> >> +     .cls = &suspend_block_sysclass,
>> >> +};
>> >> +
>> >
>> > Hmm.  Perhaps add the suspend_is_blocked() check at the beginning of
>> > sysdev_suspend() instead of this?  Surely you don't want to suspend
>> > any sysdevs with any suspend blockers active, right?
>>
>> You could make the same argument for any device. Using a sysdev makes
>> the patch easier to apply.
>
> You've lost me here. :-)

You have been making other changes to those files which made it a moving target.

> AFAICT, the only purpose of the sysdev class above is to abort suspend if
> suspend_is_blocked() returns 'true'.  If that is correct, then IMO you could
> achieve the same goal by calling suspend_is_blocked() directly from
> sysdev_suspend(), right before check_wakeup_irqs().  Or am I missing anything?

The stats patch also used it to track wakeup events, but I have added
another call for this to get rid of the sysdev.

-- 
Arve Hjønnevåg