From patchwork Thu Oct 17 16:13:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 11196369 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EA16F14E5 for ; Thu, 17 Oct 2019 16:13:59 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id D1C9E21835 for ; Thu, 17 Oct 2019 16:13:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1C9E21835 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id BD84C89F55; Thu, 17 Oct 2019 16:13:58 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by gabe.freedesktop.org (Postfix) with ESMTPS id A0C7089F55; Thu, 17 Oct 2019 16:13:57 +0000 (UTC) Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iL8PQ-0002v2-7O; Thu, 17 Oct 2019 18:13:52 +0200 Date: Thu, 17 Oct 2019 18:13:52 +0200 From: Sebastian Andrzej Siewior To: Chris Wilson Message-ID: <20191017161352.e5z3ugse7gxl5ari@linutronix.de> References: <20191017084001.w24h3lifh7ixdxe6@linutronix.de> <157130177143.4427.332333033423727237@skylake-alporthouse-com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <157130177143.4427.332333033423727237@skylake-alporthouse-com> Subject: [Intel-gfx] [PATCH v3] drm/i915: Don't disable interrupts independently of the lock X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Thomas Gleixner Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" The locks (active.lock and rq->lock) need to be taken with disabled interrupts. This is done in i915_request_retire() by disabling the interrupts independently of the locks itself. While local_irq_disable()+spin_lock() equals spin_lock_irq() on vanilla it does not on PREEMPT_RT. Chris Wilson confirmed that local_irq_disable() was just introduced as an optimisation to avoid enabling/disabling interrupts during lock/unlock combo. Enable/disable interrupts as part of the locking instruction. Cc: Chris Wilson Reviewed-by: Chris Wilson Signed-off-by: Sebastian Andrzej Siewior --- v2…v3: Rebase on top of drm-intel-next-queued v1…v2: Rebase to v5.4-rc3 drivers/gpu/drm/i915/i915_request.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index f1cadad4e81ca..4575f368455d5 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -206,14 +206,14 @@ static void remove_from_engine(struct i915_request *rq) * check that the rq still belongs to the newly locked engine. */ locked = READ_ONCE(rq->engine); - spin_lock(&locked->active.lock); + spin_lock_irq(&locked->active.lock); while (unlikely(locked != (engine = READ_ONCE(rq->engine)))) { spin_unlock(&locked->active.lock); spin_lock(&engine->active.lock); locked = engine; } list_del(&rq->sched.link); - spin_unlock(&locked->active.lock); + spin_unlock_irq(&locked->active.lock); } bool i915_request_retire(struct i915_request *rq) @@ -242,8 +242,6 @@ bool i915_request_retire(struct i915_request *rq) &i915_request_timeline(rq)->requests)); rq->ring->head = rq->postfix; - local_irq_disable(); - /* * We only loosely track inflight requests across preemption, * and so we may find ourselves attempting to retire a _completed_ @@ -252,7 +250,7 @@ bool i915_request_retire(struct i915_request *rq) */ remove_from_engine(rq); - spin_lock(&rq->lock); + spin_lock_irq(&rq->lock); i915_request_mark_complete(rq); if (!i915_request_signaled(rq)) dma_fence_signal_locked(&rq->fence); @@ -267,9 +265,7 @@ bool i915_request_retire(struct i915_request *rq) __notify_execute_cb(rq); } GEM_BUG_ON(!list_empty(&rq->execute_cb)); - spin_unlock(&rq->lock); - - local_irq_enable(); + spin_unlock_irq(&rq->lock); remove_from_client(rq); list_del(&rq->link);