On 08.07.25 14:03, Mikko Perttunen wrote:
> From: Mikko Perttunen <mperttu...@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 <mperttu...@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
>
