linux-kernel - [PATCH] dma_buf/sync_file: Enable signaling for fences when querying status

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Message-Id: <20250708-syncfile-enable-signaling-v1-1-9f6e6cd9fcda@nvidia.com>
Date: Tue, 08 Jul 2025 21:03:49 +0900
From: Mikko Perttunen <cyndis@...si.fi>
To: Sumit Semwal <sumit.semwal@...aro.org>, 
 Gustavo Padovan <gustavo@...ovan.org>, 
 Christian König <christian.koenig@....com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org, 
 Mikko Perttunen <mperttunen@...dia.com>
Subject: [PATCH] dma_buf/sync_file: Enable signaling for fences when
 querying status

From: Mikko Perttunen <mperttunen@...dia.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.

Signed-off-by: Mikko Perttunen <mperttunen@...dia.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