From patchwork Thu Oct 17 08:40:01 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: 11195155 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 751BD14DB for ; Thu, 17 Oct 2019 08:40:10 +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 5B9EA20869 for ; Thu, 17 Oct 2019 08:40:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B9EA20869 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 1B8D66EA04; Thu, 17 Oct 2019 08:40:09 +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 A3A256EA04; Thu, 17 Oct 2019 08:40:07 +0000 (UTC) Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iL1KD-0003mm-Sy; Thu, 17 Oct 2019 10:40:01 +0200 Date: Thu, 17 Oct 2019 10:40:01 +0200 From: Sebastian Andrzej Siewior To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Message-ID: <20191017084001.w24h3lifh7ixdxe6@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline Subject: [Intel-gfx] [PATCH v2] 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 , 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 Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Chris Wilson --- 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 1c5506822dc72..cf10246fb01ad 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -205,14 +205,14 @@ 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); } static bool i915_request_retire(struct i915_request *rq) @@ -272,8 +272,6 @@ static bool i915_request_retire(struct i915_request *rq) active->retire(active, rq); } - local_irq_disable(); - /* * We only loosely track inflight requests across preemption, * and so we may find ourselves attempting to retire a _completed_ @@ -282,7 +280,7 @@ static 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); @@ -297,9 +295,7 @@ static 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);