From patchwork Wed Jan 22 18:42:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11346241 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 2E7E61580 for ; Wed, 22 Jan 2020 18:43:07 +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 1778621734 for ; Wed, 22 Jan 2020 18:43:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1778621734 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk 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 8CF466F645; Wed, 22 Jan 2020 18:43:04 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id E0FBE6F646 for ; Wed, 22 Jan 2020 18:43:01 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 19974737-1500050 for multiple; Wed, 22 Jan 2020 18:42:50 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Wed, 22 Jan 2020 18:42:47 +0000 Message-Id: <20200122184249.551268-2-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200122184249.551268-1-chris@chris-wilson.co.uk> References: <20200122184249.551268-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 2/4] drm/i915: Tighten atomicity of i915_active_acquire vs i915_active_release 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" As we use a mutex to serialise the first acquire (as it may be a lengthy operation), but only an atomic decrement for the release, we have to be careful in case a second thread races and completes both acquire/release as the first finishes its acquire. Fixes: c9ad602feabe ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree") Signed-off-by: Chris Wilson --- drivers/gpu/drm/i915/i915_active.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c index 204564944dde..044be2315cbd 100644 --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -416,13 +416,15 @@ int i915_active_acquire(struct i915_active *ref) if (err) return err; - if (!atomic_read(&ref->count) && ref->active) - err = ref->active(ref); - if (!err) { - spin_lock_irq(&ref->tree_lock); /* vs __active_retire() */ - debug_active_activate(ref); - atomic_inc(&ref->count); - spin_unlock_irq(&ref->tree_lock); + if (likely(!i915_active_acquire_if_busy(ref))) { + if (ref->active) + err = ref->active(ref); + if (!err) { + spin_lock_irq(&ref->tree_lock); /* __active_retire() */ + debug_active_activate(ref); + atomic_inc(&ref->count); + spin_unlock_irq(&ref->tree_lock); + } } mutex_unlock(&ref->mutex);