From f7d219dd1c95ba9de2349b4de9f8cb510ec001cb Mon Sep 17 00:00:00 2001 From: Alex Waterman Date: Thu, 21 Jan 2016 14:50:23 -0800 Subject: gpu: nvgpu: Fix semaphore race condition A race condition existed in gk20a_channel_semaphore_wait_fd(). In some instances the semaphore underlying the sync_fence being waited on would have already signaled. This would cause the subsequent sync_fence_wait_async() call to return 1 and do nothing. Normally, the sync_fence_wait_async() call would release the newly created semaphore but in the above case that would not happen and hang any channel waiting on that semaphore. To fix this problem if sync_fence_wait_async() returns 1 immediately release the newly created semaphore. Bug 1604892 Change-Id: I1f5e811695bb099f71b7762835aba4a7e27362ec Signed-off-by: Alex Waterman Reviewed-on: http://git-master/r/935910 Reviewed-by: Automatic_Commit_Validation_User Reviewed-by: Terje Bergstrom GVS: Gerrit_Virtual_Submit --- drivers/gpu/nvgpu/gk20a/sync_gk20a.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers/gpu/nvgpu/gk20a/sync_gk20a.c') diff --git a/drivers/gpu/nvgpu/gk20a/sync_gk20a.c b/drivers/gpu/nvgpu/gk20a/sync_gk20a.c index 8740f0e2..e01c0e9a 100644 --- a/drivers/gpu/nvgpu/gk20a/sync_gk20a.c +++ b/drivers/gpu/nvgpu/gk20a/sync_gk20a.c @@ -47,8 +47,9 @@ struct gk20a_sync_pt { ktime_t dep_timestamp; /* - * A spinlock is necessary since there are times when this lock - * will be acquired in interrupt context. + * Use a spin lock here since it will have better performance + * than a mutex - there should be very little contention on this + * lock. */ spinlock_t lock; }; -- cgit v1.2.2