Re: [PATCH] drm: Honour O_NONBLOCK on the device for reading events

On Wed, 8 Jun 2011 20:14:01 +0100 Chris Wilson chris@chris-wilson.co.uk wrote:

Otherwise drmHandleEvent will block if accidentally read too often...

Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Phillip Haddad phillip.haddad@gmail.com

---

drivers/gpu/drm/drm_fops.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c index 2ec7d48..279aa95 100644 --- a/drivers/gpu/drm/drm_fops.c +++ b/drivers/gpu/drm/drm_fops.c @@ -617,6 +617,9 @@ ssize_t drm_read(struct file *filp, char __user *buffer, size_t total; ssize_t ret;

• if (filp->f_flags & O_NONBLOCK && list_empty(&file_priv->event_list))

• return -EAGAIN;
  

• ret = wait_event_interruptible(file_priv->event_wait, !list_empty(&file_priv->event_list)); if (ret < 0)

What happens if someone else empties the list between the test and the wait_event_interruptible ?