alarmtimer: Lock k_itimer during timer callback

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>

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index bb1d491..7eaf162 100644 (file)
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -448,8 +448,12 @@ static enum alarmtimer_type clock2alarm(clockid_t clockid)
 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_handle_timer(struct alarm *alarm,
        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;
 }
 
 /**