Messages in this thread | | | Date | Mon, 29 Jun 2009 11:24:07 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH] net: fix race in the receive/select |
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On Mon, Jun 29, 2009 at 11:12:33AM +0200, Andi Kleen wrote: > Jiri Olsa <jolsa@redhat.com> writes: > > > Adding memory barrier to the __pollwait function paired with > > receive callbacks. The smp_mb__after_lock define is added, > > since {read|write|spin}_lock() on x86 are full memory barriers. > > I was wondering did you see that race actually happening in practice? > If yes on which system? > > At least on x86 I can't see how it happens. mb() is only a compile > time barrier and the compiler doesn't optimize over indirect callbacks > like __pollwait() anyways. > > It might be still needed on some weaker ordered architectures, but did you > actually see it there? > > -Andi
yes, we have a customer that has been able to reproduce this problem on x86_64 CPU model Xeon E5345*2, but they didn't reproduce on XEON MV, for example.
they were able to capture a backtrace when the race happened: https://bugzilla.redhat.com/show_bug.cgi?id=494404#c1
jirka
> > -- > ak@linux.intel.com -- Speaking for myself only.
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