[PATCH][RFC v4] timekeeping: ignore the bogus sleep time if pm_trace is enabled

[Chen Yu <yu.c.chen@intel.com>]

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, please refer to:
https://patchwork.kernel.org/patch/9286365/
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.

So this patch ignores the sleep time if pm_trace is enabled in
the following situation:
1. rtc is used as persist clock to compensate for sleep time,
   (because system does not have a nonstop clocksource) or
2. rtc is used to calculate the sleep time in rtc_resume.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xunlei Pang <xlpang@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reported-by: Janek Kozicki <cosurgi@gmail.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
 arch/x86/kernel/rtc.c     |  7 +++++++
 kernel/time/timekeeping.c | 14 +++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 79c6311c..6039138 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -8,6 +8,7 @@
 #include <linux/export.h>
 #include <linux/pnp.h>
 #include <linux/of.h>
+#include <linux/pm-trace.h>
 
 #include <asm/vsyscall.h>
 #include <asm/x86_init.h>
@@ -146,6 +147,12 @@ void read_persistent_clock(struct timespec *ts)
 	x86_platform.get_wallclock(ts);
 }
 
+bool persistent_clock_is_usable(void)
+{
+	/* Unusable if pm_trace is enabled. */
+	return !((x86_platform.get_wallclock == mach_get_cmos_time) &&
+		 pm_trace_is_enabled());
+}
 
 static struct resource rtc_resources[] = {
 	[0] = {
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 3b65746..3122bd2b 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -23,6 +23,7 @@
 #include <linux/stop_machine.h>
 #include <linux/pvclock_gtod.h>
 #include <linux/compiler.h>
+#include <linux/pm-trace.h>
 
 #include "tick-internal.h"
 #include "ntp_internal.h"
@@ -1450,6 +1451,11 @@ void __weak read_boot_clock64(struct timespec64 *ts)
 	ts->tv_nsec = 0;
 }
 
+bool __weak persistent_clock_is_usable(void)
+{
+	return true;
+}
+
 /* Flag for if timekeeping_resume() has injected sleeptime */
 static bool sleeptime_injected;
 
@@ -1551,7 +1557,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
  */
 bool timekeeping_rtc_skipresume(void)
 {
-	return sleeptime_injected;
+	return sleeptime_injected || pm_trace_is_enabled();
 }
 
 /**
@@ -1662,6 +1668,12 @@ void timekeeping_resume(void)
 	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
 		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
 		sleeptime_injected = true;
+		/*
+		 * If rtc is used as persist clock thus it
+		 * would be bogus when pm_trace is enabled.
+		 */
+		if (!persistent_clock_is_usable())
+			sleeptime_injected = false;
 	}
 
 	if (sleeptime_injected)
-- 
2.7.4