* [patch] Re: RCU?: Scheduling while atomic with 3.4.23-rt33
2013-02-18 11:16 ` RCU?: Scheduling while atomic with 3.4.23-rt33 Thomas Gleixner
@ 2013-02-18 12:40 ` Tim Sander
2013-02-18 13:36 ` Tim Sander
2013-02-18 15:32 ` Steven Rostedt
2 siblings, 0 replies; 4+ messages in thread
From: Tim Sander @ 2013-02-18 12:40 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-rt-users, LKML, Paul E. McKenney, Steven Rostedt
[-- Attachment #1: Type: text/plain, Size: 1724 bytes --]
Am Montag, 18. Februar 2013, 12:16:41 schrieb Thomas Gleixner:
> On Mon, 18 Feb 2013, Tim Sander wrote:
> > Here is a transtribed backtrace for easier reading:
> > c0010fac t dump_backtrace
> > c022c188 T dump_stack
> > c022c71c t __schedule_bug
> > c022fb28 t __schedule
> > c0230644 t rt_spin_lock_slowlock
> > c0230ba8 T rt_spin_lock
> > c003a9b8 T __wake_up
> > c0052a44 t invoke_rcu_callbacks
> > c0053764 T rcu_check_callbacks
> > c0026060 T update_process_times
>
> That's due to CONFIG_TINY_PREEMPT_RCU=y. That's a known issue, which
> has been fixed in 3.6-rt.
>
> Steven, could you backport that to 3.2/3.4 please ?
As far as i see its been the waitequeue stuff. The patch below is the patch
from 3.6. backported to 3.4.
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[-- Attachment #2: 0022-rcutiny-Use-simple-waitqueue.patch --]
[-- Type: text/x-patch, Size: 2483 bytes --]
>From 2f0eb85792045f06bc0db3fe1fff17c9298240d3 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 3 Dec 2012 16:25:21 +0100
Subject: [PATCH] rcutiny: Use simple waitqueue
Simple waitqueues can be handled from interrupt disabled contexts.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/rcutiny_plugin.h | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 97e359b..2824dbd 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -26,6 +26,7 @@
#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
+#include <linux/wait-simple.h>
/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
@@ -261,7 +262,7 @@ static void show_tiny_preempt_stats(struct seq_file *m)
/* Controls for rcu_kthread() kthread. */
static struct task_struct *rcu_kthread_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
+static DEFINE_SWAIT_HEAD(rcu_kthread_wq);
static unsigned long have_rcu_kthread_work;
/*
@@ -754,7 +755,7 @@ void synchronize_rcu(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
-static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
+static DEFINE_SWAIT_HEAD(sync_rcu_preempt_exp_wq);
static unsigned long sync_rcu_preempt_exp_count;
static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
@@ -776,7 +777,7 @@ static int rcu_preempted_readers_exp(void)
*/
static void rcu_report_exp_done(void)
{
- wake_up(&sync_rcu_preempt_exp_wq);
+ swait_wake(&sync_rcu_preempt_exp_wq);
}
/*
@@ -828,8 +829,8 @@ void synchronize_rcu_expedited(void)
else {
rcu_initiate_boost();
local_irq_restore(flags);
- wait_event(sync_rcu_preempt_exp_wq,
- !rcu_preempted_readers_exp());
+ swait_event(sync_rcu_preempt_exp_wq,
+ !rcu_preempted_readers_exp());
}
/* Clean up and exit. */
@@ -917,7 +918,7 @@ static void invoke_rcu_callbacks(void)
{
have_rcu_kthread_work = 1;
if (rcu_kthread_task != NULL)
- wake_up(&rcu_kthread_wq);
+ swait_wake(&rcu_kthread_wq);
}
#ifdef CONFIG_RCU_TRACE
@@ -947,8 +948,8 @@ static int rcu_kthread(void *arg)
unsigned long flags;
for (;;) {
- wait_event_interruptible(rcu_kthread_wq,
- have_rcu_kthread_work != 0);
+ swait_event_interruptible(rcu_kthread_wq,
+ have_rcu_kthread_work != 0);
morework = rcu_boost();
local_irq_save(flags);
work = have_rcu_kthread_work;
--
1.7.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: RCU?: Scheduling while atomic with 3.4.23-rt33
2013-02-18 11:16 ` RCU?: Scheduling while atomic with 3.4.23-rt33 Thomas Gleixner
2013-02-18 12:40 ` [patch] " Tim Sander
@ 2013-02-18 13:36 ` Tim Sander
2013-02-18 15:32 ` Steven Rostedt
2 siblings, 0 replies; 4+ messages in thread
From: Tim Sander @ 2013-02-18 13:36 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-rt-users, LKML, Paul E. McKenney, Steven Rostedt
[-- Attachment #1: Type: text/plain, Size: 1052 bytes --]
Am Montag, 18. Februar 2013, 12:16:41 schrieb Thomas Gleixner:
> On Mon, 18 Feb 2013, Tim Sander wrote:
> > Here is a transtribed backtrace for easier reading:
> > c0010fac t dump_backtrace
> > c022c188 T dump_stack
> > c022c71c t __schedule_bug
> > c022fb28 t __schedule
> > c0230644 t rt_spin_lock_slowlock
> > c0230ba8 T rt_spin_lock
> > c003a9b8 T __wake_up
> > c0052a44 t invoke_rcu_callbacks
> > c0053764 T rcu_check_callbacks
> > c0026060 T update_process_times
>
> That's due to CONFIG_TINY_PREEMPT_RCU=y. That's a known issue, which
> has been fixed in 3.6-rt.
>
> Steven, could you backport that to 3.2/3.4 please ?
Mh, i just saw that i forgot to add the other patch which adds the wait-simple
stuff. Its attached so thats hopefully all to get rid of that error?
Local smoke test is running... but as its a relative rare race i'm not holding
my breath.
Btw. is that wait-simple stuff safe from irq context?
Best regards
Tim
PS: sorry for the legalese in the first mail, its just for Steven to keep him
learning german legalese ;-).
[-- Attachment #2: 0023-add-wait-simple.patch --]
[-- Type: text/x-patch, Size: 9453 bytes --]
>From 3d1861c022f159a5419a2395704fa1201c0c7c84 Mon Sep 17 00:00:00 2001
From: Tim Sander <tim.sander@hbm.com>
Date: Mon, 18 Feb 2013 13:59:21 +0100
Subject: [PATCH] add wait-simple
---
include/linux/wait-simple.h | 172 +++++++++++++++++++++++++++++++++++++++++++
kernel/Makefile | 2 +-
kernel/wait-simple.c | 119 ++++++++++++++++++++++++++++++
3 files changed, 292 insertions(+), 1 deletion(-)
create mode 100644 include/linux/wait-simple.h
create mode 100644 kernel/wait-simple.c
diff --git a/include/linux/wait-simple.h b/include/linux/wait-simple.h
new file mode 100644
index 0000000..44fee60
--- /dev/null
+++ b/include/linux/wait-simple.h
@@ -0,0 +1,172 @@
+#ifndef _LINUX_WAIT_SIMPLE_H
+#define _LINUX_WAIT_SIMPLE_H
+
+#include <linux/spinlock.h>
+#include <linux/list.h>
+
+#include <asm/current.h>
+
+struct swaiter {
+ struct task_struct *task;
+ struct list_head node;
+};
+
+#define DEFINE_SWAITER(name) \
+ struct swaiter name = { \
+ .task = current, \
+ .node = LIST_HEAD_INIT((name).node), \
+ }
+
+struct swait_head {
+ raw_spinlock_t lock;
+ struct list_head list;
+};
+
+#define SWAIT_HEAD_INITIALIZER(name) { \
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \
+ .list = LIST_HEAD_INIT((name).list), \
+ }
+
+#define DEFINE_SWAIT_HEAD(name) \
+ struct swait_head name = SWAIT_HEAD_INITIALIZER(name)
+
+extern void __init_swait_head(struct swait_head *h, struct lock_class_key *key);
+
+#define init_swait_head(swh) \
+ do { \
+ static struct lock_class_key __key; \
+ \
+ __init_swait_head((swh), &__key); \
+ } while (0)
+
+/*
+ * Waiter functions
+ */
+extern void swait_prepare_locked(struct swait_head *head, struct swaiter *w);
+extern void swait_prepare(struct swait_head *head, struct swaiter *w, int state);
+extern void swait_finish_locked(struct swait_head *head, struct swaiter *w);
+extern void swait_finish(struct swait_head *head, struct swaiter *w);
+
+/*
+ * Wakeup functions
+ */
+extern unsigned int __swait_wake(struct swait_head *head, unsigned int state, unsigned int num);
+extern unsigned int __swait_wake_locked(struct swait_head *head, unsigned int state, unsigned int num);
+
+#define swait_wake(head) __swait_wake(head, TASK_NORMAL, 1)
+#define swait_wake_interruptible(head) __swait_wake(head, TASK_INTERRUPTIBLE, 1)
+#define swait_wake_all(head) __swait_wake(head, TASK_NORMAL, 0)
+#define swait_wake_all_interruptible(head) __swait_wake(head, TASK_INTERRUPTIBLE, 0)
+
+/*
+ * Event API
+ */
+#define __swait_event(wq, condition) \
+do { \
+ DEFINE_SWAITER(__wait); \
+ \
+ for (;;) { \
+ swait_prepare(&wq, &__wait, TASK_UNINTERRUPTIBLE); \
+ if (condition) \
+ break; \
+ schedule(); \
+ } \
+ swait_finish(&wq, &__wait); \
+} while (0)
+
+/**
+ * swait_event - sleep until a condition gets true
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ *
+ * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
+ * @condition evaluates to true. The @condition is checked each time
+ * the waitqueue @wq is woken up.
+ *
+ * wake_up() has to be called after changing any variable that could
+ * change the result of the wait condition.
+ */
+#define swait_event(wq, condition) \
+do { \
+ if (condition) \
+ break; \
+ __swait_event(wq, condition); \
+} while (0)
+
+#define __swait_event_interruptible(wq, condition, ret) \
+do { \
+ DEFINE_SWAITER(__wait); \
+ \
+ for (;;) { \
+ swait_prepare(&wq, &__wait, TASK_INTERRUPTIBLE); \
+ if (condition) \
+ break; \
+ if (signal_pending(current)) { \
+ ret = -ERESTARTSYS; \
+ break; \
+ } \
+ schedule(); \
+ } \
+ swait_finish(&wq, &__wait); \
+} while (0)
+
+/**
+ * swait_event_interruptible - sleep until a condition gets true
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ *
+ * The process is put to sleep (TASK_INTERRUPTIBLE) until the
+ * @condition evaluates to true. The @condition is checked each time
+ * the waitqueue @wq is woken up.
+ *
+ * wake_up() has to be called after changing any variable that could
+ * change the result of the wait condition.
+ */
+#define swait_event_interruptible(wq, condition) \
+({ \
+ int __ret = 0; \
+ if (!(condition)) \
+ __swait_event_interruptible(wq, condition, __ret); \
+ __ret; \
+})
+
+#define __swait_event_timeout(wq, condition, ret) \
+do { \
+ DEFINE_SWAITER(__wait); \
+ \
+ for (;;) { \
+ swait_prepare(&wq, &__wait, TASK_UNINTERRUPTIBLE); \
+ if (condition) \
+ break; \
+ ret = schedule_timeout(ret); \
+ if (!ret) \
+ break; \
+ } \
+ swait_finish(&wq, &__wait); \
+} while (0)
+
+/**
+ * swait_event_timeout - sleep until a condition gets true or a timeout elapses
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ * @timeout: timeout, in jiffies
+ *
+ * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
+ * @condition evaluates to true. The @condition is checked each time
+ * the waitqueue @wq is woken up.
+ *
+ * wake_up() has to be called after changing any variable that could
+ * change the result of the wait condition.
+ *
+ * The function returns 0 if the @timeout elapsed, and the remaining
+ * jiffies if the condition evaluated to true before the timeout elapsed.
+ */
+#define swait_event_timeout(wq, condition, timeout) \
+({ \
+ long __ret = timeout; \
+ if (!(condition)) \
+ __swait_event_timeout(wq, condition, __ret); \
+ __ret; \
+})
+
+#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index f4bf68a..e7bbd15 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y = fork.o exec_domain.o panic.o printk.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o \
hrtimer.o nsproxy.o srcu.o semaphore.o \
notifier.o ksysfs.o cred.o \
- async.o range.o groups.o
+ async.o range.o groups.o wait-simple.o
ifdef CONFIG_FUNCTION_TRACER
# Do not trace debug files and internal ftrace files
diff --git a/kernel/wait-simple.c b/kernel/wait-simple.c
new file mode 100644
index 0000000..c35ec78
--- /dev/null
+++ b/kernel/wait-simple.c
@@ -0,0 +1,119 @@
+/*
+ * Simple waitqueues without fancy flags and callbacks
+ *
+ * (C) 2011 Thomas Gleixner <tglx@linutronix.de>
+ *
+ * Based on kernel/wait.c
+ *
+ * For licencing details see kernel-base/COPYING
+ */
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/wait-simple.h>
+
+/* Adds w to head->list. Must be called with head->lock locked. */
+static inline void __swait_enqueue(struct swait_head *head, struct swaiter *w)
+{
+ list_add(&w->node, &head->list);
+}
+
+/* Removes w from head->list. Must be called with head->lock locked. */
+static inline void __swait_dequeue(struct swaiter *w)
+{
+ list_del_init(&w->node);
+}
+
+/* Check whether a head has waiters enqueued */
+static inline bool swait_head_has_waiters(struct swait_head *h)
+{
+ return !list_empty(&h->list);
+}
+
+void __init_swait_head(struct swait_head *head, struct lock_class_key *key)
+{
+ raw_spin_lock_init(&head->lock);
+ lockdep_set_class(&head->lock, key);
+ INIT_LIST_HEAD(&head->list);
+}
+EXPORT_SYMBOL_GPL(__init_swait_head);
+
+void swait_prepare_locked(struct swait_head *head, struct swaiter *w)
+{
+ w->task = current;
+ if (list_empty(&w->node))
+ __swait_enqueue(head, w);
+}
+
+void swait_prepare(struct swait_head *head, struct swaiter *w, int state)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&head->lock, flags);
+ swait_prepare_locked(head, w);
+ __set_current_state(state);
+ raw_spin_unlock_irqrestore(&head->lock, flags);
+}
+EXPORT_SYMBOL_GPL(swait_prepare);
+
+void swait_finish_locked(struct swait_head *head, struct swaiter *w)
+{
+ __set_current_state(TASK_RUNNING);
+ if (w->task)
+ __swait_dequeue(w);
+}
+
+void swait_finish(struct swait_head *head, struct swaiter *w)
+{
+ unsigned long flags;
+
+ __set_current_state(TASK_RUNNING);
+ if (w->task) {
+ raw_spin_lock_irqsave(&head->lock, flags);
+ __swait_dequeue(w);
+ raw_spin_unlock_irqrestore(&head->lock, flags);
+ }
+}
+EXPORT_SYMBOL_GPL(swait_finish);
+
+unsigned int
+__swait_wake_locked(struct swait_head *head, unsigned int state, unsigned int num)
+{
+ struct swaiter *curr, *next;
+ int woken = 0;
+
+ list_for_each_entry_safe(curr, next, &head->list, node) {
+ if (wake_up_state(curr->task, state)) {
+ __swait_dequeue(curr);
+ /*
+ * The waiting task can free the waiter as
+ * soon as curr->task = NULL is written,
+ * without taking any locks. A memory barrier
+ * is required here to prevent the following
+ * store to curr->task from getting ahead of
+ * the dequeue operation.
+ */
+ smp_wmb();
+ curr->task = NULL;
+ if (++woken == num)
+ break;
+ }
+ }
+ return woken;
+}
+
+unsigned int
+__swait_wake(struct swait_head *head, unsigned int state, unsigned int num)
+{
+ unsigned long flags;
+ int woken;
+
+ if (!swait_head_has_waiters(head))
+ return 0;
+
+ raw_spin_lock_irqsave(&head->lock, flags);
+ woken = __swait_wake_locked(head, state, num);
+ raw_spin_unlock_irqrestore(&head->lock, flags);
+ return woken;
+}
+EXPORT_SYMBOL_GPL(__swait_wake);
--
1.7.9.5
^ permalink raw reply related [flat|nested] 4+ messages in thread