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SubjectRe: [PATCH] ib-release-locks-in-the-proper-order

----- "Steven Rostedt" <rostedt@goodmis.org> wrote:

> On Mon, 2009-09-21 at 21:35 +0200, John Kacur wrote:
> > Please consider the following patch - originally from Steven
> Rostedt.
> > It solves a problem for rt which is very sensitive to the lock
> ordering.
> > It should have a no impact on non-rt.
> >
> > The patch applies to current tip/master - but it is fine with me if
> it
> > would be more appropriate for one of the infiniband people to take
> it.
> >
> > Thanks
> >
> > >From e533f2b9ee9b0bd95aaa4c3369e79b350c9895d3 Mon Sep 17 00:00:00
> 2001
> > From: Steven Rostedt <srostedt@redhat.com>
> > Date: Mon, 21 Sep 2009 21:23:46 +0200
> > Subject: [PATCH] ib: release locks in the proper order
> >
> > RT is very sensitive to the order locks are taken and released
> > wrt read write locks. We must do
> >
> > lock(a);
> > lock(b);
> > lock(c);
> >
> > [...]
> >
> > unlock(c);
> > unlock(b);
> > unlock(a);
> >
> > otherwise bad things can happen.
> >
> > Signed-off-by: Ken Cox <jkc@redhat.com>
> > Signed-off-by: Clark Williams <williams@redhat.com>
> > Signed-off-by: John Kacur <jkacur@redhat.com>
>
> The -rt patch doesn't use the multi rwlock code anymore (the reason
> for
> the first patch), and the last revision of that code was able to
> handle
> that too.
>
> Linus totally ripped into this idea. A lock must be able to handle
> any
> order of unlocking. There should be no technical reason a lock must
> be
> unlocked in reverse order they were locked.
>
> What exactly is sensitive about this?
>

Thanks Steve!
I hereby withdraw this patch!!!!


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