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    Subject[PATCH 4.19 76/96] timers/sched_clock: Prevent generic sched_clock wrap caused by tick_freeze()
    Date
    From: Chang-An Chen <chang-an.chen@mediatek.com>

    commit 3f2552f7e9c5abef2775c53f7af66532f8bf65bc upstream.

    tick_freeze() introduced by suspend-to-idle in commit 124cf9117c5f ("PM /
    sleep: Make it possible to quiesce timers during suspend-to-idle") uses
    timekeeping_suspend() instead of syscore_suspend() during
    suspend-to-idle. As a consequence generic sched_clock will keep going
    because sched_clock_suspend() and sched_clock_resume() are not invoked
    during suspend-to-idle which can result in a generic sched_clock wrap.

    On a ARM system with suspend-to-idle enabled, sched_clock is registered
    as "56 bits at 13MHz, resolution 76ns, wraps every 4398046511101ns", which
    means the real wrapping duration is 8796093022202ns.

    [ 134.551779] suspend-to-idle suspend (timekeeping_suspend())
    [ 1204.912239] suspend-to-idle resume (timekeeping_resume())
    ......
    [ 1206.912239] suspend-to-idle suspend (timekeeping_suspend())
    [ 5880.502807] suspend-to-idle resume (timekeeping_resume())
    ......
    [ 6000.403724] suspend-to-idle suspend (timekeeping_suspend())
    [ 8035.753167] suspend-to-idle resume (timekeeping_resume())
    ......
    [ 8795.786684] (2)[321:charger_thread]......
    [ 8795.788387] (2)[321:charger_thread]......
    [ 0.057226] (0)[0:swapper/0]......
    [ 0.061447] (2)[0:swapper/2]......

    sched_clock was not stopped during suspend-to-idle, and sched_clock_poll
    hrtimer was not expired because timekeeping_suspend() was invoked during
    suspend-to-idle. It makes sched_clock wrap at kernel time 8796s.

    To prevent this, invoke sched_clock_suspend() and sched_clock_resume() in
    tick_freeze() together with timekeeping_suspend() and timekeeping_resume().

    Fixes: 124cf9117c5f (PM / sleep: Make it possible to quiesce timers during suspend-to-idle)
    Signed-off-by: Chang-An Chen <chang-an.chen@mediatek.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Matthias Brugger <matthias.bgg@gmail.com>
    Cc: John Stultz <john.stultz@linaro.org>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Corey Minyard <cminyard@mvista.com>
    Cc: <linux-mediatek@lists.infradead.org>
    Cc: <linux-arm-kernel@lists.infradead.org>
    Cc: Stanley Chu <stanley.chu@mediatek.com>
    Cc: <kuohong.wang@mediatek.com>
    Cc: <freddy.hsin@mediatek.com>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/1553828349-8914-1-git-send-email-chang-an.chen@mediatek.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/time/sched_clock.c | 4 ++--
    kernel/time/tick-common.c | 2 ++
    kernel/time/timekeeping.h | 7 +++++++
    3 files changed, 11 insertions(+), 2 deletions(-)

    --- a/kernel/time/sched_clock.c
    +++ b/kernel/time/sched_clock.c
    @@ -275,7 +275,7 @@ static u64 notrace suspended_sched_clock
    return cd.read_data[seq & 1].epoch_cyc;
    }

    -static int sched_clock_suspend(void)
    +int sched_clock_suspend(void)
    {
    struct clock_read_data *rd = &cd.read_data[0];

    @@ -286,7 +286,7 @@ static int sched_clock_suspend(void)
    return 0;
    }

    -static void sched_clock_resume(void)
    +void sched_clock_resume(void)
    {
    struct clock_read_data *rd = &cd.read_data[0];

    --- a/kernel/time/tick-common.c
    +++ b/kernel/time/tick-common.c
    @@ -491,6 +491,7 @@ void tick_freeze(void)
    trace_suspend_resume(TPS("timekeeping_freeze"),
    smp_processor_id(), true);
    system_state = SYSTEM_SUSPEND;
    + sched_clock_suspend();
    timekeeping_suspend();
    } else {
    tick_suspend_local();
    @@ -514,6 +515,7 @@ void tick_unfreeze(void)

    if (tick_freeze_depth == num_online_cpus()) {
    timekeeping_resume();
    + sched_clock_resume();
    system_state = SYSTEM_RUNNING;
    trace_suspend_resume(TPS("timekeeping_freeze"),
    smp_processor_id(), false);
    --- a/kernel/time/timekeeping.h
    +++ b/kernel/time/timekeeping.h
    @@ -14,6 +14,13 @@ extern u64 timekeeping_max_deferment(voi
    extern void timekeeping_warp_clock(void);
    extern int timekeeping_suspend(void);
    extern void timekeeping_resume(void);
    +#ifdef CONFIG_GENERIC_SCHED_CLOCK
    +extern int sched_clock_suspend(void);
    +extern void sched_clock_resume(void);
    +#else
    +static inline int sched_clock_suspend(void) { return 0; }
    +static inline void sched_clock_resume(void) { }
    +#endif

    extern void do_timer(unsigned long ticks);
    extern void update_wall_time(void);

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