On 2016/08/18 at 18:43, Chen Yu wrote:
> 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 <r...@rjwysocki.net>
> Cc: John Stultz <john.stu...@linaro.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Xunlei Pang <xlp...@redhat.com>
> Cc: Zhang Rui <rui.zh...@intel.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux...@vger.kernel.org
> Suggested-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> Reported-by: Janek Kozicki <cosu...@gmail.com>
> Signed-off-by: Chen Yu <yu.c.c...@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;
> +}
> +
I suddenly think of a way to avoid adding this ugly __weak auxiliary function.
Add a special treatment for read_persistent_clock() in arch/x86/kernel/rtc.c as
follows,
void read_persistent_clock(struct timespec *ts)
{
x86_platform.get_wallclock(ts);
/* Make rtc-based persistent clock unusable if pm_trace is enabled. */
if (pm_trace_is_enabled() &&
x86_platform.get_wallclock == mach_get_cmos_time) {
ts->tv_sec = 0;
ts->tv_nsec = 0;
}
}
In this way, we can avoid the touch of timekeeping core, after all ptrace is
currently x86-specific.
What do you think?
Regards,
Xunlei
> /* 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)
