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drm/nouveau/pm/fan: drop the fan lock in fan_update() before rescheduling

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This should fix a deadlock that has been reported to us where fan_update()
would hold the fan lock and try to grab the alarm_program_lock to reschedule
an update. On an other CPU, the alarm_program_lock would have been taken
before calling fan_update(), leading to a deadlock.

We should Cc: <stable@vger.kernel.org> # 3.9+

Reported-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Tested-by: Timothée Ravier <tim@siosm.fr>
Tested-by: Boris Fersing (IRC nick fersingb, no public email address)
Signed-off-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Martin Peres 2014-03-14 00:26:52 +01:00 committed by Ben Skeggs
parent 6c3252bc83
commit 61679fe153
1 changed files with 13 additions and 6 deletions
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19
drivers/gpu/drm/nouveau/core/subdev/therm/fan.c
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@ -54,8 +54,10 @@ nouveau_fan_update(struct nouveau_fan *fan, bool immediate, int target)
/* check that we're not already at the target duty cycle */
duty = fan->get(therm);
if (duty == target)
goto done;
if (duty == target) {
spin_unlock_irqrestore(&fan->lock, flags);
return 0;
}
/* smooth out the fanspeed increase/decrease */
if (!immediate && duty >= 0) {
@ -73,8 +75,15 @@ nouveau_fan_update(struct nouveau_fan *fan, bool immediate, int target)
nv_debug(therm, "FAN update: %d\n", duty);
ret = fan->set(therm, duty);
if (ret)
goto done;
if (ret) {
spin_unlock_irqrestore(&fan->lock, flags);
return ret;
}
/* fan speed updated, drop the fan lock before grabbing the
* alarm-scheduling lock and risking a deadlock
*/
spin_unlock_irqrestore(&fan->lock, flags);
/* schedule next fan update, if not at target speed already */
if (list_empty(&fan->alarm.head) && target != duty) {
@ -92,8 +101,6 @@ nouveau_fan_update(struct nouveau_fan *fan, bool immediate, int target)
ptimer->alarm(ptimer, delay * 1000 * 1000, &fan->alarm);
}
done:
spin_unlock_irqrestore(&fan->lock, flags);
return ret;
}