Re: lockdep splat from ioctl and mmap fops sharing lock

[Stefan Richter]

Johannes Weiner wrote:
> Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx> writes:
>
> > Johannes Weiner wrote:
> > > raw1394_ioctl() doing usercopy under fi->state_mutex
> > > raw1394_mmap() taking fi->state_mutex under mmap_sem
...
> > was the usage of mmap_sem changed after 2.6.27 or were my tests
> > insufficient?
>
> In linux-next/-mm, copy_to/from_user have lockdep annotations telling
> that they might fault and therefor acquire the mmap_sem in #PF.
>
> But since faults on ioctl parameters are so rare, without these
> annotations you would probably never see a warning.

Thanks for the report and explanation.  I logged this as 
http://bugzilla.kernel.org/show_bug.cgi?id=11823 (dv1394, won't fix) and 
http://bugzilla.kernel.org/show_bug.cgi?id=11824 (raw1394, to be fixed 
in the 2.6.28-rc timeframe since it is a post 2.6.27 regression).
--
Stefan Richter
-=====-==--- =-=- ==--=
http://arcgraph.de/sr/
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