Re: [PATCH 5/7] Fix double call to pthread_mutex_unlock in _treefs_s_dir_lookup.

[Neal H. Walfield]

At Mon, 17 Dec 2012 01:31:32 +0100,
Samuel Thibault wrote:
> 
> Cyril Roelandt, le Mon 17 Dec 2012 00:51:28 +0100, a écrit :
> > * libtreefs/dir-lookup.c (_treefs_s_dir_lookup): remove a redundant call to
> > pthread_mutex_unlock.
> > 
> > Signed-off-by: Cyril Roelandt <tipecaml@gmail.com>
> > ---
> >  libtreefs/dir-lookup.c |    1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/libtreefs/dir-lookup.c b/libtreefs/dir-lookup.c
> > index ce2acaf..41c34ea 100644
> > --- a/libtreefs/dir-lookup.c
> > +++ b/libtreefs/dir-lookup.c
> > @@ -199,7 +199,6 @@ _treefs_s_dir_lookup (struct treefs_handle *h,
> >          in the right order. */
> >       if (strcmp (path, "..") != 0)
> >         {
> > -         pthread_mutex_unlock (&node->lock);
> >           pthread_mutex_lock (&dir->lock);
> >           pthread_mutex_lock (&node->lock);
> 
> At quick sight I don't think this one is spurious, see the comment: this
> code seems to be used when one wants to lock dir->lock, which we can
> not do when we already have node->lock, that's why we have to release
> node->lock before taking dir->lock again.

I would change this to do a trylock on dir->lock.  If that fails, then
unlock node->lock and relock dir->lock and node->lock.

Neal