From: Chris Wilson Date: Tue, 3 Dec 2019 15:26:31 +0000 (+0000) Subject: drm/i915/execlists: Skip nested spinlock for validating pending X-Git-Tag: v5.6-rc1~114^2~17^2~215 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=49e74c8f9ae635a1c87fab06966da4c713cf9d63;p=thirdparty%2Fkernel%2Flinux.git drm/i915/execlists: Skip nested spinlock for validating pending 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 Cc: Tvrtko Ursulin Fixes: c95d31c3df1b ("drm/i915/execlists: Lock the request while validating it during promotion") Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20191203152631.3107653-2-chris@chris-wilson.co.uk --- diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 37ab9742abe71..82807918382d4 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;