The patch titled
timerfd: really wake up processes when timer is cancelled on clock change
has been added to the -mm tree. Its filename is
timerfd-really-wake-up-processes-when-timer-is-cancelled-on-clock-change.patch
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------------------------------------------------------
Subject: timerfd: really wake up processes when timer is cancelled on clock change
From: Max Asbock <masbock@xxxxxxxxxxxxxxxxxx>
When the system time is set the clock_was_set() function calls
timerfd_clock_was_set() to cancel and wake up processes waiting on
potential cancelable timerfd timers. However the wake up currently has no
effect because in the case of timerfd_read it is dependent on ctx->ticks
not being 0. timerfd_poll also requires ctx->ticks being non zero. As a
consequence processes waiting on cancelable timers only get woken up when
the timers expire. This patch fixes this by incrementing ctx->ticks
before calling wake_up.
Signed-off-by: Max Asbock <masbock@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <>
---
fs/timerfd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff -puN fs/timerfd.c~timerfd-really-wake-up-processes-when-timer-is-cancelled-on-clock-change fs/timerfd.c
--- a/fs/timerfd.c~timerfd-really-wake-up-processes-when-timer-is-cancelled-on-clock-change
+++ a/fs/timerfd.c
@@ -61,7 +61,9 @@ static enum hrtimer_restart timerfd_tmrp
/*
* Called when the clock was set to cancel the timers in the cancel
- * list.
+ * list. This will wake up processes waiting on these timers. The
+ * wake-up requires ctx->ticks to be non zero, therefore we increment
+ * it before calling wake_up_locked().
*/
void timerfd_clock_was_set(void)
{
@@ -76,6 +78,7 @@ void timerfd_clock_was_set(void)
spin_lock_irqsave(&ctx->wqh.lock, flags);
if (ctx->moffs.tv64 != moffs.tv64) {
ctx->moffs.tv64 = KTIME_MAX;
+ ctx->ticks++;
wake_up_locked(&ctx->wqh);
}
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
_
Patches currently in -mm which might be from masbock@xxxxxxxxxxxxxxxxxx are
timerfd-really-wake-up-processes-when-timer-is-cancelled-on-clock-change.patch
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