time: Fix extra sleeptime injection when suspend fails

Currently, there exists a corner case assuming when there is
only one clocksource e.g RTC, and system failed to go to
suspend mode. While resume rtc_resume() injects the sleeptime
as timekeeping_rtc_skipresume() returned 'false' (default value
of sleeptime_injected) due to which we can see mismatch in
timestamps.

This issue can also come in a system where more than one
clocksource are present and very first suspend fails.

Success case:
------------
                                        {sleeptime_injected=false}
rtc_suspend() => timekeeping_suspend() => timekeeping_resume() =>

(sleeptime injected)
 rtc_resume()

Failure case:
------------
         {failure in sleep path} {sleeptime_injected=false}
rtc_suspend()     =>          rtc_resume()

{sleeptime injected again which was not required as the suspend failed}

Fix this by handling the boolean logic properly.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 7033ac1..19414b1 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1519,8 +1519,20 @@ void __weak read_boot_clock64(struct timespec64 *ts)
        ts->tv_nsec = 0;
 }
 
-/* Flag for if timekeeping_resume() has injected sleeptime */
-static bool sleeptime_injected;
+/*
+ * Flag reflecting whether timekeeping_resume() has injected sleeptime.
+ *
+ * The flag starts of false and is only set when a suspend reaches
+ * timekeeping_suspend(), timekeeping_resume() sets it to false when the
+ * timekeeper clocksource is not stopping across suspend and has been
+ * used to update sleep time. If the timekeeper clocksource has stopped
+ * then the flag stays true and is used by the RTC resume code to decide
+ * whether sleeptime must be injected and if so the flag gets false then.
+ *
+ * If a suspend fails before reaching timekeeping_resume() then the flag
+ * stays false and prevents erroneous sleeptime injection.
+ */
+static bool suspend_timing_needed;
 
 /* Flag for if there is a persistent clock on this platform */
 static bool persistent_clock_exists;
@@ -1619,7 +1631,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
  */
 bool timekeeping_rtc_skipresume(void)
 {
-       return sleeptime_injected;
+       return !suspend_timing_needed;
 }
 
 /**
@@ -1655,6 +1667,8 @@ void timekeeping_inject_sleeptime64(const struct timespec64 *delta)
        raw_spin_lock_irqsave(&timekeeper_lock, flags);
        write_seqcount_begin(&tk_core.seq);
 
+       suspend_timing_needed = false;
+
        timekeeping_forward_now(tk);
 
        __timekeeping_inject_sleeptime(tk, delta);
@@ -1679,8 +1693,8 @@ void timekeeping_resume(void)
        unsigned long flags;
        struct timespec64 ts_new, ts_delta;
        u64 cycle_now;
+       bool inject_sleeptime = false;
 
-       sleeptime_injected = false;
        read_persistent_clock64(&ts_new);
 
        clockevents_resume();
@@ -1710,14 +1724,16 @@ void timekeeping_resume(void)
                                              tk->tkr_mono.mask);
                nsec = mul_u64_u32_shr(cyc_delta, clock->mult, clock->shift);
                ts_delta = ns_to_timespec64(nsec);
-               sleeptime_injected = true;
+               inject_sleeptime = true;
        } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
                ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
-               sleeptime_injected = true;
+               inject_sleeptime = true;
        }
 
-       if (sleeptime_injected)
+       if (inject_sleeptime) {
+               suspend_timing_needed = false;
                __timekeeping_inject_sleeptime(tk, &ts_delta);
+       }
 
        /* Re-base the last cycle value */
        tk->tkr_mono.cycle_last = cycle_now;
@@ -1752,6 +1768,8 @@ int timekeeping_suspend(void)
        if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)
                persistent_clock_exists = true;
 
+       suspend_timing_needed = true;
+
        raw_spin_lock_irqsave(&timekeeper_lock, flags);
        write_seqcount_begin(&tk_core.seq);
        timekeeping_forward_now(tk);