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Commit 74fa0af4 authored by Chris Wilson's avatar Chris Wilson Committed by Alistair Strachan
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BACKPORT: dma-buf/sync_file: Allow multiple sync_files to wrap a single dma-fence 



Up until recently sync_file were create to export a single dma-fence to
userspace, and so we could canabalise a bit insie dma-fence to mark
whether or not we had enable polling for the sync_file itself. However,
with the advent of syncobj, we do allow userspace to create multiple
sync_files for a single dma-fence. (Similarly, that the sw-sync
validation framework also started returning multiple sync-files wrapping
a single dma-fence for a syncpt also triggering the problem.)

This patch reverts my suggestion in commit e2416553
("dma-buf/sync_file: only enable fence signalling on poll()") to use a
single bit in the shared dma-fence and restores the sync_file->flags for
tracking the bits individually.

Reported-by: default avatarGustavo Padovan <gustavo.padovan@collabora.com>
Fixes: f1e8c67123cf ("dma-buf/sw-sync: Use an rbtree to sort fences in the timeline")
Fixes: e9083420bbac ("drm: introduce sync objects (v4)")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarGustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170728212951.7818-1-chris@chris-wilson.co.uk


[astrachan: rediffed against changed context lines in 4.9]
Bug: 79383895
Change-Id: If98fa920693045fdab21886960657bbe8ef550c0
Signed-off-by: default avatarAlistair Strachan <astrachan@google.com>
parent c2f9bce9

drivers/dma-buf/sync_file.c

+3 −2
Original line number Diff line number Diff line
@@ -279,7 +279,7 @@ static void sync_file_free(struct kref *kref) 
	struct sync_file *sync_file = container_of(kref, struct sync_file,

						     kref);



	if (test_bit(POLL_ENABLED, &sync_file->fence->flags))

	if (test_bit(POLL_ENABLED, &sync_file->flags))

		fence_remove_callback(sync_file->fence, &sync_file->cb);

	fence_put(sync_file->fence);

	kfree(sync_file);
@@ -299,7 +299,8 @@ static unsigned int sync_file_poll(struct file *file, poll_table *wait) 


	poll_wait(file, &sync_file->wq, wait);



	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {

	if (list_empty(&sync_file->cb.node) &&

	    !test_and_set_bit(POLL_ENABLED, &sync_file->flags)) {

		if (fence_add_callback(sync_file->fence, &sync_file->cb,

					   fence_check_cb_func) < 0)

			wake_up_all(&sync_file->wq);

include/linux/sync_file.h

+2 −1
Original line number Diff line number Diff line
@@ -40,12 +40,13 @@ struct sync_file { 
#endif



	wait_queue_head_t	wq;

	unsigned long		flags;



	struct fence		*fence;

	struct fence_cb cb;

};



#define POLL_ENABLED FENCE_FLAG_USER_BITS

#define POLL_ENABLED 0



struct sync_file *sync_file_create(struct fence *fence);

struct fence *sync_file_get_fence(int fd);