[ 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 chris@chris-wilson.co.uk Cc: Daniel Vetter daniel.vetter@ffwll.ch Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20170804082328.17173-1-chris@c... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/drm_fops.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c index c37b7b5f1dd31..921f7f690ae9b 100644 --- a/drivers/gpu/drm/drm_fops.c +++ b/drivers/gpu/drm/drm_fops.c @@ -515,6 +515,7 @@ ssize_t drm_read(struct file *filp, char __user *buffer, 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; }