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    Subject[PATCH 3.2 049/102] alarmtimer: Lock k_itimer during timer callback
    3.2.64-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Richard Larocque <rlarocque@google.com>

    commit 474e941bed9262f5fa2394f9a4a67e24499e5926 upstream.

    Locks the k_itimer's it_lock member when handling the alarm timer's
    expiry callback.

    The regular posix timers defined in posix-timers.c have this lock held
    during timout processing because their callbacks are routed through
    posix_timer_fn(). The alarm timers follow a different path, so they
    ought to grab the lock somewhere else.

    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Richard Cochran <richardcochran@gmail.com>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Cc: Sharvil Nanavati <sharvil@google.com>
    Signed-off-by: Richard Larocque <rlarocque@google.com>
    Signed-off-by: John Stultz <john.stultz@linaro.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    kernel/time/alarmtimer.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    --- a/kernel/time/alarmtimer.c
    +++ b/kernel/time/alarmtimer.c
    @@ -448,8 +448,12 @@ static enum alarmtimer_type clock2alarm(
    static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
    ktime_t now)
    {
    + unsigned long flags;
    struct k_itimer *ptr = container_of(alarm, struct k_itimer,
    it.alarm.alarmtimer);
    + enum alarmtimer_restart result = ALARMTIMER_NORESTART;
    +
    + spin_lock_irqsave(&ptr->it_lock, flags);
    if ((ptr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) {
    if (posix_timer_event(ptr, 0) != 0)
    ptr->it_overrun++;
    @@ -459,9 +463,11 @@ static enum alarmtimer_restart alarm_han
    if (ptr->it.alarm.interval.tv64) {
    ptr->it_overrun += alarm_forward(alarm, now,
    ptr->it.alarm.interval);
    - return ALARMTIMER_RESTART;
    + result = ALARMTIMER_RESTART;
    }
    - return ALARMTIMER_NORESTART;
    + spin_unlock_irqrestore(&ptr->it_lock, flags);
    +
    + return result;
    }

    /**


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