drm/i915/execlists: Flush tasklet directly from reset-finish (9e4fa012) · Commits · 戴 / test

On finishing the reset, the intention is to restart the GPU before we relinquish the forcewake taken to handle the reset - the goal being the GPU reloads a context before it is allowed to sleep. For this purpose, we used tasklet_flush() which although it accomplished the goal of restarting the GPU, carried with it a sting in its tail: it cleared the TASKLET_STATE_SCHED bit. This meant that if another CPU queued a new request to this engine, we would clear the flag and later attempt to requeue the tasklet on the local CPU, breaking the per-cpu softirq lists. Remove the dangerous tasklet_kill() and just run the tasklet func directly as we know it is safe to do so (the tasklets are internally locked to allow mixed usage from direct submission). Signed-off-by:

Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Cc: Michel Thierry <michel.thierry@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Reviewed-by:

Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180828152702.27536-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.h

+0 −6

Original line number	Diff line number	Diff line
		@@ -82,12 +82,6 @@ static inline void __tasklet_disable_sync_once(struct tasklet_struct *t)
		tasklet_unlock_wait(t);
		}

		static inline void __tasklet_enable_sync_once(struct tasklet_struct *t)
		{
		if (atomic_dec_return(&t->count) == 0)
		tasklet_kill(t);
		}

		static inline bool __tasklet_is_enabled(const struct tasklet_struct *t)
		{
		return !atomic_read(&t->count);

drivers/gpu/drm/i915/intel_lrc.c

+6 −11

Original line number	Diff line number	Diff line
		@@ -1962,21 +1962,16 @@ static void execlists_reset_finish(struct intel_engine_cs *engine)
		{
		struct intel_engine_execlists * const execlists = &engine->execlists;

		/* After a GPU reset, we may have requests to replay */
		if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
		tasklet_schedule(&execlists->tasklet);

		/*
		* Flush the tasklet while we still have the forcewake to be sure
		* that it is not allowed to sleep before we restart and reload a
		* context.
		* After a GPU reset, we may have requests to replay. Do so now while
		* we still have the forcewake to be sure that the GPU is not allowed
		* to sleep before we restart and reload a context.
		*
		* As before (with execlists_reset_prepare) we rely on the caller
		* serialising multiple attempts to reset so that we know that we
		* are the only one manipulating tasklet state.
		*/
		__tasklet_enable_sync_once(&execlists->tasklet);
		if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
		execlists->tasklet.func(execlists->tasklet.data);

		tasklet_enable(&execlists->tasklet);
		GEM_TRACE("%s: depth->%d\n", engine->name,
		atomic_read(&execlists->tasklet.count));
		}

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