From 8eb4704b124cbd44f189709959137d77063ecfa1 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sun, 3 Nov 2019 16:23:05 +0000 Subject: [PATCH] drm/i915: Protect request peeking with RCU Since the execlists_active() is no longer protected by the engine->active.lock, we need to protect the request pointer with RCU to prevent it being freed as we evaluate whether or not we need to preempt. Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock") Fixes: 13ed13a4dcbf ("drm/i915: Don't set queue_priority_hint if we don't kick the submission") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Tvrtko Ursulin Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20191104090158.2959-2-chris@chris-wilson.co.uk (cherry picked from commit 7d148635253328dda7cfe55d57e3c828e9564427) Signed-off-by: Joonas Lahtinen --- drivers/gpu/drm/i915/i915_scheduler.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c index d2edb52..010d67f 100644 --- a/drivers/gpu/drm/i915/i915_scheduler.c +++ b/drivers/gpu/drm/i915/i915_scheduler.c @@ -202,21 +202,26 @@ static void kick_submission(struct intel_engine_cs *engine, if (prio <= engine->execlists.queue_priority_hint) return; + rcu_read_lock(); + /* Nothing currently active? We're overdue for a submission! */ inflight = execlists_active(&engine->execlists); if (!inflight) - return; + goto unlock; /* * If we are already the currently executing context, don't * bother evaluating if we should preempt ourselves. */ if (inflight->hw_context == rq->hw_context) - return; + goto unlock; engine->execlists.queue_priority_hint = prio; if (need_preempt(prio, rq_prio(inflight))) tasklet_hi_schedule(&engine->execlists.tasklet); + +unlock: + rcu_read_unlock(); } static void __i915_schedule(struct i915_sched_node *node, -- 2.7.4