From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756439Ab3CAAq6 (ORCPT ); Thu, 28 Feb 2013 19:46:58 -0500 Received: from mail-pb0-f41.google.com ([209.85.160.41]:50980 "EHLO mail-pb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756273Ab3CAAoP (ORCPT ); Thu, 28 Feb 2013 19:44:15 -0500 From: John Stultz To: lkml Cc: Erik Gilling , Maarten Lankhorst , Daniel Vetter , Rob Clark , Sumit Semwal , Greg KH , dri-devel@lists.freedesktop.org, Android Kernel Team , John Stultz Subject: [PATCH 22/30] staging: sync: Protect unlocked access to fence status Date: Thu, 28 Feb 2013 16:43:18 -0800 Message-Id: <1362098606-26469-23-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1362098606-26469-1-git-send-email-john.stultz@linaro.org> References: <1362098606-26469-1-git-send-email-john.stultz@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Erik Gilling Fence status is checked outside of locks in both sync_fence_wait and sync_fence_poll. This patch adds propper barrier protection in these cases to avoid seeing stale status. Cc: Maarten Lankhorst Cc: Erik Gilling Cc: Daniel Vetter Cc: Rob Clark Cc: Sumit Semwal Cc: Greg KH Cc: dri-devel@lists.freedesktop.org Cc: Android Kernel Team Signed-off-by: Erik Gilling Signed-off-by: John Stultz --- drivers/staging/android/sync.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/staging/android/sync.c b/drivers/staging/android/sync.c index 36ffa20..2394189 100644 --- a/drivers/staging/android/sync.c +++ b/drivers/staging/android/sync.c @@ -556,6 +556,16 @@ int sync_fence_cancel_async(struct sync_fence *fence, } EXPORT_SYMBOL(sync_fence_cancel_async); +static bool sync_fence_check(struct sync_fence *fence) +{ + /* + * Make sure that reads to fence->status are ordered with the + * wait queue event triggering + */ + smp_rmb(); + return fence->status != 0; +} + int sync_fence_wait(struct sync_fence *fence, long timeout) { int err = 0; @@ -563,7 +573,7 @@ int sync_fence_wait(struct sync_fence *fence, long timeout) if (timeout > 0) { timeout = msecs_to_jiffies(timeout); err = wait_event_interruptible_timeout(fence->wq, - fence->status != 0, + sync_fence_check(fence), timeout); } else if (timeout < 0) { err = wait_event_interruptible(fence->wq, fence->status != 0); @@ -630,6 +640,12 @@ static unsigned int sync_fence_poll(struct file *file, poll_table *wait) poll_wait(file, &fence->wq, wait); + /* + * Make sure that reads to fence->status are ordered with the + * wait queue event triggering + */ + smp_rmb(); + if (fence->status == 1) return POLLIN; else if (fence->status < 0) -- 1.7.10.4