| Message ID | 20191203152631.3107653-2-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] drm/i915/execlists: Add a couple more validity checks to assert_pending() | expand |
Quoting Chris Wilson (2019-12-03 15:26:31) > Only along the submission path can we guarantee that the locked request > is indeed from a foreign engine, and so the nesting of engine/rq is > permissible. On the submission tasklet (process_csb()), we may find > ourselves competing with the normal nesting of rq/engine, invalidating > our nesting. As we only use the spinlock for debug purposes, skip the > debug if we cannot acquire the spinlock for safe validation - catching > 99% of the bugs is better than causing a hard lockup. > Fixes: c95d31c3df1b ("drm/i915/execlists: Lock the request while validating it during promotion") > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> -Chris
Quoting Chris Wilson (2019-12-03 15:26:31) > Only along the submission path can we guarantee that the locked request > is indeed from a foreign engine, and so the nesting of engine/rq is > permissible. On the submission tasklet (process_csb()), we may find > ourselves competing with the normal nesting of rq/engine, invalidating > our nesting. As we only use the spinlock for debug purposes, skip the > debug if we cannot acquire the spinlock for safe validation - catching > 99% of the bugs is better than causing a hard lockup. > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> -Chris
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 37ab9742abe7..82807918382d 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1315,8 +1315,8 @@ assert_pending_valid(const struct intel_engine_execlists *execlists, ce = rq->hw_context; /* Hold tightly onto the lock to prevent concurrent retires! */ - spin_lock_irqsave_nested(&rq->lock, flags, - SINGLE_DEPTH_NESTING); + if (!spin_trylock_irqsave(&rq->lock, flags)) + continue; if (i915_request_completed(rq)) goto unlock;
Only along the submission path can we guarantee that the locked request is indeed from a foreign engine, and so the nesting of engine/rq is permissible. On the submission tasklet (process_csb()), we may find ourselves competing with the normal nesting of rq/engine, invalidating our nesting. As we only use the spinlock for debug purposes, skip the debug if we cannot acquire the spinlock for safe validation - catching 99% of the bugs is better than causing a hard lockup. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> --- drivers/gpu/drm/i915/gt/intel_lrc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)