[Devel] Re: [PATCH] Wake up mandatory locks waiter on chmod (v2)

[J. Bruce Fields]

On Tue, Sep 18, 2007 at 10:33:26AM +0400, Pavel Emelyanov wrote:
> Trond Myklebust wrote:
> > IOW: the process that is waiting in locks_mandatory_area() will be
> > released as soon as the advisory lock is dropped. If that theory is
> > broken in practice, then that is the bug that we need to fix. We neither
> > want to add a load of locking crap to notify_change(), nor should we
> > need to.
> 
> We have this for inotify already. Adding wakeup for mandatory lock
> is not that bad.
> 
> Anyway - I noticed, that the system state can become not consistent
> and proposed the way to fix it. If this inconsistency is not a big
> deal, and nobody cares, than I'm fine with forgetting this patch, 
> since I have no other arguments to protect it, but "this is just not
> very nice without this patch".

Maybe this should be documented, e.g. in fcntl(2).  I'm not sure exactly
what we'd say--we probably don't want to commit to the current behavior.
Maybe something like "behavior is undefined when setting or clearing
mandatory locking on a file while it is locked".

--b.