From: Chris Wilson Date: Fri, 4 Aug 2017 08:23:28 +0000 (+0100) Subject: drm: Wake up next in drm_read() chain if we are forced to putback the event X-Git-Tag: v4.19.47~5 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=00734a9e7329acc48e575f697ee4118998c1dac0;p=platform%2Fkernel%2Flinux-rpi3.git drm: Wake up next in drm_read() chain if we are forced to putback the event [ Upstream commit 60b801999c48b6c1dd04e653a38e2e613664264e ] After an event is sent, we try to copy it into the user buffer of the first waiter in drm_read() and if the user buffer doesn't have enough room we put it back onto the list. However, we didn't wake up any subsequent waiter, so that event may sit on the list until either a new vblank event is sent or a new waiter appears. Rare, but in the worst case may lead to a stuck process. Testcase: igt/drm_read/short-buffer-wakeup Signed-off-by: Chris Wilson Cc: Daniel Vetter Reviewed-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20170804082328.17173-1-chris@chris-wilson.co.uk Signed-off-by: Sasha Levin --- diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index e4ccb52..334adda 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -567,6 +567,7 @@ put_back_event: file_priv->event_space -= length; list_add(&e->link, &file_priv->event_list); spin_unlock_irq(&dev->event_lock); + wake_up_interruptible(&file_priv->event_wait); break; }