On 08.07.25 14:03, Mikko Perttunen wrote:

From: Mikko Perttunen mperttunen@nvidia.com

dma_fence_get_status is not guaranteed to return valid information on if the fence has been signaled or not if SW signaling has not been enabled for the fence. To ensure valid information is reported, enable SW signaling for fences before getting their status.

I don't know how often I had to rejected that patch now, we really need to improve the documentation :(

The fence info query exists to query the status *without* enabling signaling, that is the whole purpose of the function!

If you want to enable signaling *and* query the status then just poll on the sync file file descriptor with a zero timeout.

If the signaling timestamp or error code is needed then that can be retrieved after signaling through the info IOCTL.

Regards, Christian.

Signed-off-by: Mikko Perttunen mperttunen@nvidia.com

drivers/dma-buf/sync_file.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c index 747e377fb95417ddd506b528618a4288bea9d459..a6fd1d14dde155561b9fd2c07e6aa20dc9863a8d 100644 --- a/drivers/dma-buf/sync_file.c +++ b/drivers/dma-buf/sync_file.c @@ -271,6 +271,8 @@ static int sync_fill_fence_info(struct dma_fence *fence, const char __rcu *timeline; const char __rcu *driver;

• dma_fence_enable_sw_signaling(fence);
• rcu_read_lock();

driver = dma_fence_driver_name(fence); @@ -320,6 +322,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file, * info->num_fences. */ if (!info.num_fences) {

• dma_fence_enable_sw_signaling(sync_file->fence);
  

  info.status = dma_fence_get_status(sync_file->fence); goto no_fences; } else {

---

base-commit: 58ba80c4740212c29a1cf9b48f588e60a7612209 change-id: 20250708-syncfile-enable-signaling-a993acff1860