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From: John Stultz <john.stultz@linaro.org>
To: lkml <linux-kernel@vger.kernel.org>
Cc: Erik Gilling <konkers@android.com>,
	Maarten Lankhorst <maarten.lankhorst@canonical.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Rob Clark <robclark@gmail.com>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	dri-devel@lists.freedesktop.org,
	Android Kernel Team <kernel-team@android.com>,
	John Stultz <john.stultz@linaro.org>
Subject: [PATCH 22/30] staging: sync: Protect unlocked access to fence status
Date: Thu, 28 Feb 2013 16:43:18 -0800	[thread overview]
Message-ID: <1362098606-26469-23-git-send-email-john.stultz@linaro.org> (raw)
In-Reply-To: <1362098606-26469-1-git-send-email-john.stultz@linaro.org>

From: Erik Gilling <konkers@android.com>

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 <maarten.lankhorst@canonical.com>
Cc: Erik Gilling <konkers@android.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rob Clark <robclark@gmail.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: dri-devel@lists.freedesktop.org
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Erik Gilling <konkers@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 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


  parent reply	other threads:[~2013-03-01  0:46 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-01  0:42 [RFC][PATCH 00/30] staging: Android sync driver John Stultz
2013-03-01  0:42 ` [PATCH 01/30] staging: sync: Add synchronization framework John Stultz
2013-03-01  0:42 ` [PATCH 02/30] staging: sw_sync: Add cpu based sync driver John Stultz
2013-03-01  0:42 ` [PATCH 03/30] staging: sync: Add timestamps to sync_pts John Stultz
2013-03-01  0:43 ` [PATCH 04/30] staging: sync: Add debugfs support John Stultz
2013-03-01  0:43 ` [PATCH 05/30] staging: sw_sync: Add debug support John Stultz
2013-03-01  0:43 ` [PATCH 06/30] staging: sync: Add ioctl to get fence data John Stultz
2013-03-01  0:43 ` [PATCH 07/30] staging: sw_sync: Add fill_driver_data support John Stultz
2013-03-01  0:43 ` [PATCH 08/30] staging: sync: Add poll support John Stultz
2013-03-01  0:43 ` [PATCH 09/30] staging: sync: Allow async waits to be canceled John Stultz
2013-03-01  0:43 ` [PATCH 10/30] staging: sync: Export sync API symbols John Stultz
2013-03-01  2:00   ` Greg KH
2013-03-01  3:59     ` John Stultz
2013-03-01  8:21       ` Erik Gilling
2013-03-01 13:55         ` Greg KH
2013-03-01 16:30           ` Erik Gilling
2013-03-01 22:47         ` Erik Gilling
2013-03-01  0:43 ` [PATCH 11/30] staging: sw_sync: Export sw_sync API John Stultz
2013-03-01  0:43 ` [PATCH 12/30] staging: sync: Reorder sync_fence_release John Stultz
2013-03-01  0:43 ` [PATCH 13/30] staging: sync: Optimize fence merges John Stultz
2013-03-01  0:43 ` [PATCH 14/30] staging: sync: Add internal refcounting to fences John Stultz
2013-03-01  0:43 ` [PATCH 15/30] staging: sync: Add reference counting to timelines John Stultz
2013-03-01  0:43 ` [PATCH 16/30] staging: sync: Fix error paths John Stultz
2013-03-01  0:43 ` [PATCH 17/30] staging: sw_sync: " John Stultz
2013-03-01  0:43 ` [PATCH 18/30] staging: sync: Change wait timeout to mirror poll semantics John Stultz
2013-03-01  0:43 ` [PATCH 19/30] staging: sync: Dump sync state to console on timeout John Stultz
2013-03-01  0:43 ` [PATCH 20/30] staging: sync: Improve timeout dump messages John Stultz
2013-03-01  0:43 ` [PATCH 21/30] staging: sync: Dump sync state on fence errors John Stultz
2013-03-01  0:43 ` John Stultz [this message]
2013-03-01  0:43 ` [PATCH 23/30] staging: sync: Update new fence status with sync_fence_signal_pt John Stultz
2013-03-01  0:43 ` [PATCH 24/30] staging: sync: Use proper barriers when waiting indefinitely John Stultz
2013-03-01  0:43 ` [PATCH 25/30] staging: sync: Refactor sync debug printing John Stultz
2013-03-01  0:43 ` [PATCH 26/30] staging: sw_sync: Convert to use new value_str debug ops John Stultz
2013-03-01  0:43 ` [PATCH 27/30] staging: sync: Add tracepoint support John Stultz
2013-03-01  0:43 ` [PATCH 28/30] staging: sync: Fix race condition between merge and signal John Stultz
2013-03-01  0:43 ` [PATCH 29/30] staging: sync: Don't log wait timeouts when timeout = 0 John Stultz
2013-03-01  0:43 ` [PATCH 30/30] staging: sync: Fix timeout = 0 wait behavior John Stultz
2013-03-01  1:59 ` [RFC][PATCH 00/30] staging: Android sync driver Greg KH
2013-03-01 16:20   ` Erik Gilling
2013-03-03 18:42 ` Daniel Vetter
2013-03-03 18:52   ` animelovin

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