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 e24165537312
("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: Gustavo Padovan <[email protected]>
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: Chris Wilson <[email protected]>
Cc: Sumit Semwal <[email protected]>
Cc: Sean Paul <[email protected]>
Cc: Gustavo Padovan <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v4.13-rc1+
Signed-off-by: Gustavo Padovan <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit db1fc97ca0c0d3fdeeadf314d99a26188438940a)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index d7e219d2669daf01c935bd18c0836cb88a34e075..66fb40d0ebdbbec521499cd58cf2e1d55c195878 100644 (file)
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -304,7 +304,7 @@ static int sync_file_release(struct inode *inode, struct file *file)
 {
        struct sync_file *sync_file = file->private_data;
 
-       if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
+       if (test_bit(POLL_ENABLED, &sync_file->flags))
                dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
        dma_fence_put(sync_file->fence);
        kfree(sync_file);
@@ -318,7 +318,8 @@ 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 (dma_fence_add_callback(sync_file->fence, &sync_file->cb,
                                           fence_check_cb_func) < 0)
                        wake_up_all(&sync_file->wq);

diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index 5726107963b2d9930d61c3cf5c486abfe244c18a..0ad87c434ae6a344984837e8dd053fe7705d21f1 100644 (file)
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -43,12 +43,13 @@ struct sync_file {
 #endif
 
        wait_queue_head_t       wq;
+       unsigned long           flags;
 
        struct dma_fence        *fence;
        struct dma_fence_cb cb;
 };
 
-#define POLL_ENABLED DMA_FENCE_FLAG_USER_BITS
+#define POLL_ENABLED 0
 
 struct sync_file *sync_file_create(struct dma_fence *fence);
 struct dma_fence *sync_file_get_fence(int fd);