On Sunday 14 November 2010 23:48:51 Hans Verkuil wrote: > On Sunday, November 14, 2010 22:53:29 Arnd Bergmann wrote: > > On Sunday 14 November 2010, Hans Verkuil wrote: > > > This patch series converts 24 v4l drivers to unlocked_ioctl. These are low > > > hanging fruit but you have to start somewhere :-) > > > > > > The first patch replaces mutex_lock in the V4L2 core by mutex_lock_interruptible > > > for most fops. > > > > The patches all look good as far as I can tell, but I suppose the title is > > obsolete now that the BKL has been replaced with a v4l-wide mutex, which > > is what you are removing in the series. > > I guess I have to rename it, even though strictly speaking the branch I'm > working in doesn't have your patch merged yet. > > BTW, replacing the BKL with a static mutex is rather scary: the BKL gives up > the lock whenever you sleep, the mutex doesn't. Since sleeping is very common > in V4L (calling VIDIOC_DQBUF will typically sleep while waiting for a new frame > to arrive), this will make it impossible for another process to access any > v4l2 device node while the ioctl is sleeping. > > I am not sure whether that is what you intended. Or am I missing something? I was aware that something like this could happen, but I apparently misjudged how big the impact is. The general pattern for ioctls is that those that get called frequently do not sleep, so it can almost always be called with a mutex held. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
