Messages in this thread | ![/](/images/icornerl.gif) | | Date | Fri, 23 Apr 2010 20:24:28 +1000 | Subject | Re: Locking question for DRM | From | Dave Airlie <> |
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On Fri, Apr 23, 2010 at 8:22 PM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > > Various bits of the DRM deal with minor->master: > > In the case of the open helper its protected by the struct mutex. > > In the release path it's protected on some paths, but not this one ... > > /* if the master has gone away we can't do anything with the lock */ > if (file_priv->minor->master) > drm_master_release(dev, filp); > > and I can't see what makes this safe if the drm_release for the master > and a client occur at the same time ?
lock_kernel in drm_release. We probably need to clean that up.
> > The setmaster/dropmaster ioctl seems similar - the various conditional > checks are not protected from parallel changes occuring during their > execution. > > Is this a bug or is something clever afoot ?
These ioctls are also under the BKL.
So yes its nasty, and we should probably grow a minor lock to protect that.
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