From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 71C0DC98309 for ; Wed, 23 Sep 2026 11:15:21 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8B92910EF97; Wed, 23 Sep 2026 11:15:18 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=lankhorst.se header.i=@lankhorst.se header.b="eDcwCDai"; dkim-atps=neutral Received: from lankhorst.se (unknown [141.105.120.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 60AE910E87E for ; Wed, 23 Sep 2026 11:15:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lankhorst.se; s=default; t=1790162115; bh=xCWtunRcRhi49jxpjFiRYl9YRfVOHVETkfd5QFcr8qk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eDcwCDaiXtd/wNc9eqm05L8vVyYKR3XsXs59h4Oe4CT9wcv+swQsKq7HPwJtnMCcF MiKaE9R0z2s5eeiSIWloFk9akI8gy+/4ysxUesr9GBD3jX+x1jDCuRJm2uzqvylvmm kbZ8DQjhyi06m01BKSVbb/4lH3bVXKJk6NNUKYMXaHubzXjH6PKS4jsiofrjUuTWFk F79P/+BdxRT88NZ69A+IBes26Vql03H/Gwzhl2Jp2Ei4FAC7h65dRoM7zDQPKlcF6u NOUipEcyzWrMRVKsQ/fedW53hl44c9cbeqMmYD+EATJIiojgFiD+Upf6k/rRNOJg7c hXY5bTi5JhY0Q== From: Maarten Lankhorst To: Sebastian Andrzej Siewior , Joonas Lahtinen , Tvrtko Ursulin , intel-gfx@lists.freedesktop.org Cc: Clark Williams , Maarten Lankhorst , Maarten Lankhorst Subject: [PATCH v5 1/6] drm/i915/gt: Use spin_lock_irq() instead of local_irq_disable() + spin_lock() Date: Wed, 23 Sep 2026 13:15:20 +0200 Message-ID: <20260923111518.310430-9-dev@lankhorst.se> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923111518.310430-8-dev@lankhorst.se> References: <20260923111518.310430-8-dev@lankhorst.se> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" From: Sebastian Andrzej Siewior execlists_dequeue() is invoked from a function which uses local_irq_disable() to disable interrupts so the spin_lock() behaves like spin_lock_irq(). This breaks PREEMPT_RT because local_irq_disable() + spin_lock() is not the same as spin_lock_irq(). execlists_dequeue_irq() and execlists_dequeue() has each one caller only. If intel_engine_cs::active::lock is acquired and released with the _irq suffix then it behaves almost as if execlists_dequeue() would be invoked with disabled interrupts. The difference is the last part of the function which is then invoked with enabled interrupts. I can't tell if this makes a difference. From looking at it, it might work to move the last unlock at the end of the function as I didn't find anything that would acquire the lock again. Reported-by: Clark Williams Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Maarten Lankhorst Signed-off-by: Maarten Lankhorst --- .../drm/i915/gt/intel_execlists_submission.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c index e693b0c9d2a3e..841f719326756 100644 --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c @@ -1300,7 +1300,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * and context switches) submission. */ - spin_lock(&sched_engine->lock); + spin_lock_irq(&sched_engine->lock); /* * If the queue is higher priority than the last @@ -1400,7 +1400,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * Even if ELSP[1] is occupied and not worthy * of timeslices, our queue might be. */ - spin_unlock(&sched_engine->lock); + spin_unlock_irq(&sched_engine->lock); return; } } @@ -1426,7 +1426,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) if (last && !can_merge_rq(last, rq)) { spin_unlock(&ve->base.sched_engine->lock); - spin_unlock(&engine->sched_engine->lock); + spin_unlock_irq(&engine->sched_engine->lock); return; /* leave this for another sibling */ } @@ -1588,7 +1588,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) */ sched_engine->queue_priority_hint = queue_prio(sched_engine); i915_sched_engine_reset_on_empty(sched_engine); - spin_unlock(&sched_engine->lock); + spin_unlock_irq(&sched_engine->lock); /* * We can skip poking the HW if we ended up with exactly the same set @@ -1614,13 +1614,6 @@ static void execlists_dequeue(struct intel_engine_cs *engine) } } -static void execlists_dequeue_irq(struct intel_engine_cs *engine) -{ - local_irq_disable(); /* Suspend interrupts across request submission */ - execlists_dequeue(engine); - local_irq_enable(); /* flush irq_work (e.g. breadcrumb enabling) */ -} - static void clear_ports(struct i915_request **ports, int count) { memset_p((void **)ports, NULL, count); @@ -2475,7 +2468,7 @@ static void execlists_submission_tasklet(struct tasklet_struct *t) } if (!engine->execlists.pending[0]) { - execlists_dequeue_irq(engine); + execlists_dequeue(engine); start_timeslice(engine); } -- 2.55.0