When we merge several fences, if all of them are signaled already, we
still keep one of them. So instead of using add_fence(), which will not
increase the refcount of signaled fences, we should explicitly call
fence_get() for the fence we are keeping.
This patch fixes a kernel panic that can be triggered by creating a fence that
is expired (or increasing the timeline until it expires), then creating a
merged fence out of it, and deleting the merged fence. This will make the
original expired fence's refcount go to zero.
Testcase: igt/sw_sync/sync_expired_merge
Signed-off-by: Rafael Antognolli <rafael.antognolli@xxxxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
---
drivers/dma-buf/sync_file.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index abb5fda..0fe7ec2 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -253,10 +253,8 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
for (; i_b < b_num_fences; i_b++)
add_fence(fences, &i, b_fences[i_b]);
- if (i == 0) {
- add_fence(fences, &i, a_fences[0]);
- i++;
- }
+ if (i == 0)
+ fences[i++] = fence_get(a_fences[0]);
if (num_fences > i) {
nfences = krealloc(fences, i * sizeof(*fences),
--
2.7.4
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