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staging: sync: Protect unlocked access to fence status

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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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Erik Gilling
2013-02-28 16:43:18 -08:00
committed by Greg Kroah-Hartman
parent 7560645406
commit c679212dbf
1 changed files with 17 additions and 1 deletions
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18
drivers/staging/android/sync.c
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@@ -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)