Eric Lee / linux-smarc-t335x-v3.2

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Commit 1123d93963cbd2546449d4d9f0c568e323cb0ac6

Authored by Max Asbock
Committed by Thomas Gleixner
1 parent 2c53b436a3
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

timerfd: Fix wakeup of processes when timer is cancelled on clock change 

Currently processes waiting with poll on cancelable timerfd timers are
not woken up when the timers are canceled. 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@linux.vnet.ibm.com>
Cc: kay.sievers@vrfy.org
Cc: virtuoso@slind.org
Cc: johnstul <johnstul@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1307985512.4710.41.camel@w-amax.beaverton.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Showing 1 changed file with 4 additions and 1 deletions Side-by-side Diff

... ... @@ -61,7 +61,9 @@
61 61  
62 62 /*
63 63 * Called when the clock was set to cancel the timers in the cancel
64   - * list.
  64 + * list. This will wake up processes waiting on these timers. The
  65 + * wake-up requires ctx->ticks to be non zero, therefore we increment
  66 + * it before calling wake_up_locked().
65 67 */
66 68 void timerfd_clock_was_set(void)
67 69 {
... ... @@ -76,6 +78,7 @@
76 78 spin_lock_irqsave(&ctx->wqh.lock, flags);
77 79 if (ctx->moffs.tv64 != moffs.tv64) {
78 80 ctx->moffs.tv64 = KTIME_MAX;
  81 + ctx->ticks++;
79 82 wake_up_locked(&ctx->wqh);
80 83 }
81 84 spin_unlock_irqrestore(&ctx->wqh.lock, flags);