alarmtimer: Lock k_itimer during timer callback

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: stable@vger.kernel.org
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>

1 files changed, 8 insertions, 2 deletions

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 41a925396830..a7077d3ae52f 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -464,8 +464,12 @@ 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++;
@@ -475,9 +479,11 @@ 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;
 }
 
 /**