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

From: Chen Yu
Date: Thu Aug 18 2016 - 06:36:52 EST


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@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Xunlei Pang <xlpang@xxxxxxxxxx>
Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Reported-by: Janek Kozicki <cosurgi@xxxxxxxxx>
Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
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