Op 11-07-16 om 22:27 schreef Gustavo Padovan: > 2016-07-10 Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>: > >> Op 08-07-16 om 17:44 schreef Gustavo Padovan: >>> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx> >>> >>> Signalling doesn't need to be enabled at sync_file creation, it is only >>> required if userspace waiting the fence to signal through poll(). >>> >>> Thus we delay fence_add_callback() until poll is called. It only adds the >>> callback the first time poll() is called. This avoid re-adding the same >>> callback multiple times. >>> >>> v2: rebase and update to work with new fence support for sync_file >>> >>> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx> >>> --- >>> This patch applies on top of my latest sync_file changes to support >>> fence_array: https://lkml.org/lkml/2016/7/4/534 >>> >>> drivers/dma-buf/sync_file.c | 23 ++++++++++++++--------- >>> include/linux/sync_file.h | 2 ++ >>> 2 files changed, 16 insertions(+), 9 deletions(-) >>> >>> diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c >>> index 61a687c..1db4a64 100644 >>> --- a/drivers/dma-buf/sync_file.c >>> +++ b/drivers/dma-buf/sync_file.c >>> @@ -86,8 +86,6 @@ struct sync_file *sync_file_create(struct fence *fence) >>> fence->ops->get_timeline_name(fence), fence->context, >>> fence->seqno); >>> >>> - fence_add_callback(fence, &sync_file->cb, fence_check_cb_func); >>> - >>> return sync_file; >>> } >>> EXPORT_SYMBOL(sync_file_create); >>> @@ -269,9 +267,6 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a, >>> goto err; >>> } >>> >>> - fence_add_callback(sync_file->fence, &sync_file->cb, >>> - fence_check_cb_func); >>> - >>> strlcpy(sync_file->name, name, sizeof(sync_file->name)); >>> return sync_file; >>> >>> @@ -286,7 +281,6 @@ static void sync_file_free(struct kref *kref) >>> struct sync_file *sync_file = container_of(kref, struct sync_file, >>> kref); >>> >>> - fence_remove_callback(sync_file->fence, &sync_file->cb); >>> fence_put(sync_file->fence); >>> kfree(sync_file); >>> } >>> @@ -306,13 +300,24 @@ static unsigned int sync_file_poll(struct file *file, poll_table *wait) >>> >>> poll_wait(file, &sync_file->wq, wait); >>> >>> + if (!sync_file->enabled) { >>> + fence_add_callback(sync_file->fence, &sync_file->cb, >>> + fence_check_cb_func); >>> + sync_file->enabled = true; >>> + } >> Won't this blow up completely with 2 threads polling at the same time? > Indeed, using atomic operations on enabled should fix this. No, it still would blow up without locking around fence_remove/add_callback too.. Personally I would just add the callback once, then remove it in destructor. Something like: poll: if (!atomic_xchg(&sync_file->enabled, 1)) { if (fence_add_callback(...) < 0) wake up sync_file->wq, fence is signaled } sync_file_free: if (atomic_read(&sync_file->enabled)) fence_remove_callback(...); fence_put() It's not like fence can disable hw signaling when all callbacks are removed anyway, it's harmless to keep it on the list. ~Maarten _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
