sync: protect unlocked access to fence status
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.
Change-Id: I9d8b6ce6accb415e797df58068a1ccd54e6be445
Signed-off-by: Erik Gilling <konkers@android.com>
diff --git a/drivers/base/sync.c b/drivers/base/sync.c
index 326e184..4c5689b 100644
--- a/drivers/base/sync.c
+++ b/drivers/base/sync.c
@@ -556,6 +556,16 @@
}
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 @@
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);
@@ -627,6 +637,12 @@
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)