[PATCH][RFC v7] timekeeping: Ignore the bogus sleep time if pm_trace is enabled

* [PATCH][RFC v7] timekeeping: Ignore the bogus sleep time if pm_trace is enabled
@ 2016-11-10  4:55 Chen Yu
  2016-11-10 16:32 ` Pavel Machek
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Chen Yu @ 2016-11-10  4:55 UTC (permalink / raw)
  To: linux-pm
  Cc: x86, linux-kernel, rtc-linux, Chen Yu, Rafael J. Wysocki,
	John Stultz, Xunlei Pang, Ingo Molnar, Len Brown, H. Peter Anvin,
	Pavel Machek, Thomas Gleixner

Previously we encountered some memory overflow issues due to
the bogus sleep time brought by inconsistent rtc, which is
triggered when pm_trace is enabled, and we have fixed it
in recent kernel. However it's improper in the first place
to call __timekeeping_inject_sleeptime() in case that pm_trace
is enabled simply because that "hash" time value will wreckage
the timekeeping subsystem.

This patch is originally written by Thomas, which would bypass
the bogus rtc interval when pm_trace is enabled.
Meanwhile, if system succeed to resume back with pm_trace set, the
users are warned to adjust the bogus rtc either by ntp-date or rdate,
by resetting pm_trace_rtc_abused to false, otherwise above tools might
not work as expected.

Originally-from: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Xunlei Pang <xlpang@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
 arch/x86/kernel/rtc.c       |  9 +++++++++
 drivers/base/power/trace.c  | 27 +++++++++++++++++++++++++++
 drivers/rtc/rtc-cmos.c      |  7 +++++++
 include/linux/mc146818rtc.h |  1 +
 include/linux/pm-trace.h    |  9 ++++++++-
 5 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 79c6311c..898383c 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec *now)
 	unsigned int status, year, mon, day, hour, min, sec, century = 0;
 	unsigned long flags;
 
+	/*
+	 * If pm trace abused the RTC as storage set the timespec to 0
+	 * which tells the caller that this RTC value is bogus.
+	 */
+	if (!pm_trace_rtc_valid()) {
+		now->tv_sec = now->tv_nsec = 0;
+		return;
+	}
+
 	spin_lock_irqsave(&rtc_lock, flags);
 
 	/*
diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index efec10b..209e214 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -10,6 +10,7 @@
 #include <linux/pm-trace.h>
 #include <linux/export.h>
 #include <linux/rtc.h>
+#include <linux/suspend.h>
 
 #include <linux/mc146818rtc.h>
 
@@ -74,6 +75,9 @@
 
 #define DEVSEED (7919)
 
+bool pm_trace_rtc_abused __read_mostly;
+EXPORT_SYMBOL(pm_trace_rtc_abused);
+
 static unsigned int dev_hash_value;
 
 static int set_magic_time(unsigned int user, unsigned int file, unsigned int device)
@@ -104,6 +108,7 @@ static int set_magic_time(unsigned int user, unsigned int file, unsigned int dev
 	time.tm_min = (n % 20) * 3;
 	n /= 20;
 	mc146818_set_time(&time);
+	pm_trace_rtc_abused = true;
 	return n ? -1 : 0;
 }
 
@@ -238,10 +243,32 @@ int show_trace_dev_match(char *buf, size_t size)
 	device_pm_unlock();
 	return ret;
 }
+static int pm_trace_notify(struct notifier_block *nb,
+				unsigned long mode, void *_unused)
+{
+	switch (mode) {
+	case PM_POST_HIBERNATION:
+	case PM_POST_SUSPEND:
+		if (pm_trace_rtc_abused) {
+			pm_trace_rtc_abused = false;
+			pr_warn("Possible incorrect RTC due to pm_trace,"
+				"please use ntp-date or rdate to reset.\n");
+		}
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+static struct notifier_block pm_trace_nb = {
+	.notifier_call = pm_trace_notify,
+};
 
 static int early_resume_init(void)
 {
 	hash_value_early_read = read_magic_time();
+	register_pm_notifier(&pm_trace_nb);
 	return 0;
 }
 
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index dd3d598..3d9aedc 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -191,6 +191,13 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
 
 static int cmos_read_time(struct device *dev, struct rtc_time *t)
 {
+	/*
+	 * If pmtrace abused the RTC for storage tell the caller that it is
+	 * unusable.
+	 */
+	if (!pm_trace_rtc_valid())
+		return -EIO;
+
 	/* REVISIT:  if the clock has a "century" register, use
 	 * that instead of the heuristic in mc146818_get_time().
 	 * That'll make Y3K compatility (year > 2070) easy!
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index a585b4b..0661af1 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -16,6 +16,7 @@
 #include <asm/mc146818rtc.h>		/* register access macros */
 #include <linux/bcd.h>
 #include <linux/delay.h>
+#include <linux/pm-trace.h>
 
 #ifdef __KERNEL__
 #include <linux/spinlock.h>		/* spinlock_t */
diff --git a/include/linux/pm-trace.h b/include/linux/pm-trace.h
index ecbde7a..7b78793 100644
--- a/include/linux/pm-trace.h
+++ b/include/linux/pm-trace.h
@@ -1,11 +1,17 @@
 #ifndef PM_TRACE_H
 #define PM_TRACE_H
 
+#include <linux/types.h>
 #ifdef CONFIG_PM_TRACE
 #include <asm/pm-trace.h>
-#include <linux/types.h>
 
 extern int pm_trace_enabled;
+extern bool pm_trace_rtc_abused;
+
+static inline bool pm_trace_rtc_valid(void)
+{
+	return !pm_trace_rtc_abused;
+}
 
 static inline int pm_trace_is_enabled(void)
 {
@@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *buf, size_t size);
 
 #else
 
+static inline bool pm_trace_rtc_valid(void) { return true; }
 static inline int pm_trace_is_enabled(void) { return 0; }
 
 #define TRACE_DEVICE(dev) do { } while (0)
-- 
2.7.4

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