drm/i915: Take request reference before arming the watchdog timer

Reference needs to be taken before arming the timer. Luckily, given the
default timer period of 20s, the potential to hit the race is extremely
unlikely.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 9b4d0598ee94 ("drm/i915: Request watchdog infrastructure")
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210326105759.2387104-1-tvrtko.ursulin@linux.intel.com

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 9165971c3c47a9b6d2c9501cc2b7d7449dd207b6..bec9c3652188b47dd5ee0c7969ee87c49f29965c 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -350,6 +350,8 @@ static void __rq_arm_watchdog(struct i915_request *rq)
        if (!ce->watchdog.timeout_us)
                return;
 
+       i915_request_get(rq);
+
        hrtimer_init(&wdg->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        wdg->timer.function = __rq_watchdog_expired;
        hrtimer_start_range_ns(&wdg->timer,
@@ -357,7 +359,6 @@ static void __rq_arm_watchdog(struct i915_request *rq)
                                           NSEC_PER_USEC),
                               NSEC_PER_MSEC,
                               HRTIMER_MODE_REL);
-       i915_request_get(rq);
 }
 
 static void __rq_cancel_watchdog(struct i915_request *rq)