From: Dominik Behr dbehr@chromium.org

To avoid hanging userspace components that might have been waiting on the active fences of the destroyed timeline we need to signal with error all remaining fences on such timeline.

This restore the default behaviour of the Android sw_sync framework, which Android still relies on. It was broken on the dma fence conversion a few years ago and never fixed.

v2: Do not bother with cleanup do the list (Chris Wilson)

Signed-off-by: Dominik Behr dbehr@chromium.org Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.com --- drivers/dma-buf/sw_sync.c | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index 38cc7389a6c1..f183eef074fd 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -321,9 +321,19 @@ static int sw_sync_debugfs_open(struct inode *inode, struct file *file) static int sw_sync_debugfs_release(struct inode *inode, struct file *file) { struct sync_timeline *obj = file->private_data; + struct sync_pt *pt, *next;

smp_wmb();

+ spin_lock_irq(&obj->lock); + + list_for_each_entry_safe(pt, next, &obj->pt_list, link) { + dma_fence_set_error(&pt->base, -ENOENT); + dma_fence_signal_locked(&pt->base); + } + + spin_unlock_irq(&obj->lock); + sync_timeline_put(obj); return 0; }

Quoting Gustavo Padovan (2017-09-07 20:02:45)

From: Emilio López emilio.lopez@collabora.co.uk

If a sw_sync_timeline is destroyed the fences associated to it need to be signalled. This test checks that.

Cc: Shuah Khan shuah@kernel.org Cc: linux-kselftest@vger.kernel.org Signed-off-by: Emilio López emilio.lopez@collabora.co.uk Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.com

---

tools/testing/selftests/sync/sync_test.c | 1 + tools/testing/selftests/sync/sync_wait.c | 58 ++++++++++++++++++++++++++++++++ tools/testing/selftests/sync/synctest.h | 1 + 3 files changed, 60 insertions(+)

diff --git a/tools/testing/selftests/sync/sync_test.c b/tools/testing/selftests/sync/sync_test.c index 62fa666e501a..5d93c9dcc290 100644 --- a/tools/testing/selftests/sync/sync_test.c +++ b/tools/testing/selftests/sync/sync_test.c @@ -79,6 +79,7 @@ int main(void) err += RUN_TEST(test_fence_one_timeline_merge); err += RUN_TEST(test_fence_merge_same_fence); err += RUN_TEST(test_fence_multi_timeline_wait);

•   err += RUN_TEST(test_fence_wait_on_destroyed_timeline);
    err += RUN_TEST(test_stress_two_threads_shared_timeline);
    err += RUN_TEST(test_consumer_stress_multi_producer_single_consumer);
    err += RUN_TEST(test_merge_stress_random_merge);
  

diff --git a/tools/testing/selftests/sync/sync_wait.c b/tools/testing/selftests/sync/sync_wait.c index d69b752f6550..82ad9f519959 100644 --- a/tools/testing/selftests/sync/sync_wait.c +++ b/tools/testing/selftests/sync/sync_wait.c @@ -25,6 +25,7 @@

• OTHER DEALINGS IN THE SOFTWARE.

*/

+#include <pthread.h> #include "sync.h" #include "sw_sync.h" #include "synctest.h" @@ -89,3 +90,60 @@ int test_fence_multi_timeline_wait(void)

    return 0;

}

+struct fds_test {

•   int timeline;
  

•   int fencesig, fencekill;
  

•   int result;
  

+};

+static int test_fence_wait_on_destroyed_timeline_thread(void *d)

A horrible cast later just because you didn't want to use s/int/void */

+{

•   struct fds_test *data = d;
  

•   int ret;
  

•   /* in case of errors */
  

•   data->result = 1;
  

•   ret = sw_sync_timeline_inc(data->timeline, 100);
  

•   ASSERT(ret == 0, "Failure advancing timeline\n");
  

Just return the error, e.g. return "err string"; Only allow explosions from the main thread.

•   ret = sync_wait(data->fencekill, -1);
  

•   ASSERT(ret == 1, "Failure waiting on fence\n");
  

•   /* no errors occurred */
  

•   data->result = 0;
  

•   return 0;
  

+}

+int test_fence_wait_on_destroyed_timeline(void) +{

•   struct fds_test data;
  

•   pthread_t thread;
  

•   int valid;
  

•   data.timeline = sw_sync_timeline_create();
  

•   valid = sw_sync_timeline_is_valid(data.timeline);
  

•   ASSERT(valid, "Failure allocating timeline\n");
  

•   data.fencesig = sw_sync_fence_create(data.timeline, "allocFence", 100);
  

•   data.fencekill = sw_sync_fence_create(data.timeline, "allocFence", 200);
  

•   /* Spawn a thread to wait on a fence when the timeline is killed */
  

•   pthread_create(&thread, NULL, (void *(*)(void *))
  

•                  test_fence_wait_on_destroyed_timeline_thread, &data);
  

•   /* Wait for the thread to spool up */
  

•   sync_wait(data.fencesig, -1);
  

•   /* Kill the timeline */
  

•   sw_sync_timeline_destroy(data.timeline);
  

•   /* wait for the thread to clean up */
  

•   pthread_join(thread, NULL);
  

So in case of bug, we block forever. That suggests that you want to use a timeout, 10s? -Chris