From patchwork Fri Mar 29 02:45:00 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Simon Horman X-Patchwork-Id: 2363891 Return-Path: X-Original-To: patchwork-ltsi-dev@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) by patchwork1.kernel.org (Postfix) with ESMTP id 93D2C3FD40 for ; Fri, 29 Mar 2013 02:59:38 +0000 (UTC) Received: from mail.linux-foundation.org (localhost [IPv6:::1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 5991B93A; Fri, 29 Mar 2013 02:48:12 +0000 (UTC) X-Original-To: ltsi-dev@lists.linuxfoundation.org Delivered-To: ltsi-dev@mail.linuxfoundation.org Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTP id 53353DD0 for ; Fri, 29 Mar 2013 02:48:00 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from kirsty.vergenet.net (kirsty.vergenet.net [202.4.237.240]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 1B45C20188 for ; Fri, 29 Mar 2013 02:47:55 +0000 (UTC) Received: from ayumi.akashicho.tokyo.vergenet.net (p8120-ipbfp1001kobeminato.hyogo.ocn.ne.jp [118.10.137.120]) by kirsty.vergenet.net (Postfix) with ESMTP id C95962C6A19; Fri, 29 Mar 2013 13:46:05 +1100 (EST) Received: by ayumi.akashicho.tokyo.vergenet.net (Postfix, from userid 7100) id 708C7EDEA2B; Fri, 29 Mar 2013 11:46:04 +0900 (JST) From: Simon Horman To: ltsi-dev@lists.linuxfoundation.org Date: Fri, 29 Mar 2013 11:45:00 +0900 Message-Id: <1364525119-31791-372-git-send-email-horms+renesas@verge.net.au> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1364525119-31791-1-git-send-email-horms+renesas@verge.net.au> References: <1364525119-31791-1-git-send-email-horms+renesas@verge.net.au> X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_LOW, RP_MATCHES_RCVD autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Magnus Damm Subject: [LTSI-dev] [PATCH/RFC 371/390] drm/rcar-du: Fix race condition between page flip request and handler X-BeenThere: ltsi-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: "A list to discuss patches, development, and other things related to the LTSI project" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: ltsi-dev-bounces@lists.linuxfoundation.org Errors-To: ltsi-dev-bounces@lists.linuxfoundation.org From: Laurent Pinchart The page flip handler stores the page flip event pointer and then calls drm_vblank_get() to enable the vblank interrupt. Due to the vblank off delay, the vblank interrupt can be enabled in the hardware at that point, even if the vblank reference count is equal to 0. If a vblank interrupt is triggered between storing the event pointer and calling drm_vblank_get(), the page flip completion handler will process the event and call drm_vblank_put() with a reference count equal to 0. This will result in a BUG_ON. Fix the race condition by calling drm_vblank_get() before storing the event pointer. Signed-off-by: Laurent Pinchart (cherry picked from commit 667ca8e2f58236b166aff4c1575ea38c5e3be91c) Signed-off-by: Simon Horman --- drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c index 99578a7..934e6a5 100644 --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c @@ -393,10 +393,10 @@ static int rcar_du_crtc_page_flip(struct drm_crtc *crtc, if (event) { event->pipe = 0; + drm_vblank_get(dev, 0); spin_lock_irqsave(&dev->event_lock, flags); rcrtc->event = event; spin_unlock_irqrestore(&dev->event_lock, flags); - drm_vblank_get(dev, 0); } return 0;