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    Subject[PATCH] timerfd: really wake up processes when timer is cancelled on clock change
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    Date
    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>
    ---

    --- linux-3.0-rc1/fs/timerfd.c
    +++ linux-3.0-rc1.timerfd/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);

    --
    Max Asböck


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