Messages in this thread | | | Date | Mon, 21 Sep 2009 17:48:36 -0400 (EDT) | From | John Kacur <> | Subject | Re: [PATCH] ib-release-locks-in-the-proper-order |
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----- "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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