Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

[Vasiliy Kulikov]

On Thu, Feb 16, 2012 at 22:34 +0400, Cyrill Gorcunov wrote:
> On Thu, Feb 16, 2012 at 10:21:06PM +0400, Vasiliy Kulikov wrote:
> > On Thu, Feb 16, 2012 at 20:49 +0400, Cyrill Gorcunov wrote:
> > > +	err = mutex_lock_killable(m1);
> > > +	if (!err && likely(m1 != m2)) {
> > > +		err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);
> > 
> > Doesn't it lead to a deadlock?
> > 
> > mutex_lock_killable(task1)
> > |					mutex_lock_killable(task2)
> > mutex_lock_killable_nested(task2)	|
> > (locked)				|
> > 					mutex_lock_killable_nested(task1)
> > 					(locked)
> > 
> > I suppose you should use some global lock (kcmp_lock) before both locks.
> 
> but here is if (m1 > m2) and swap() do take place.

Ah, ok.  Then this deadlock scenario is impossible, sorry.

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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