From: Joe Buehler <aspam@cox.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: kernel panic in fib_rules_lookup [2.6.27.7 vendor-patched]
Date: Tue, 26 Oct 2010 09:29:48 -0400 [thread overview]
Message-ID: <4CC6D7CC.5040608@cox.net> (raw)
In-Reply-To: <1287851745.2658.364.camel@edumazet-laptop>
Eric Dumazet wrote:
> With a normal workload, on a dual cpu machine, a missing memory barrier
> can stay un-noticed for quite a long time. The race window is so small
> that probability for the bug might be 0.0000001 % or something like
> that :(
I'm looking at the LINUX source at the moment and not liking what I see
in include/asm-mips/barrier.h:
#define smp_mb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#ifdef CONFIG_CPU_CAVIUM_OCTEON
#define smp_rmb() barrier()
#define smp_wmb() barrier()
#else
#define smp_rmb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#define smp_wmb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#endif
The Octeon documentation explicitly says that neither loads nor stores
need execute in program order, so the definitions for smp_rmb and
smp_wmb appear to be wrong wrong wrong.
It appears that smp_wmb should be making use of SYNCW and smp_rmb should
be making use of SYNC.
Should I pursue this question on the main LINUX kernel list?
Joe Buehler
next prev parent reply other threads:[~2010-10-26 13:29 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-12 17:14 kernel panic in fib_rules_lookup [2.6.27.7 vendor-patched] Joe Buehler
2010-10-12 17:40 ` Eric Dumazet
2010-10-13 11:18 ` Joe Buehler
2010-10-20 17:43 ` Joe Buehler
2010-10-20 22:05 ` Eric Dumazet
2010-10-22 20:30 ` Joe Buehler
2010-10-23 3:44 ` Eric Dumazet
2010-10-23 15:11 ` Eric Dumazet
2010-10-23 15:24 ` Eric Dumazet
2010-10-23 15:40 ` Joe Buehler
2010-10-23 16:07 ` Eric Dumazet
2010-10-23 15:33 ` Joe Buehler
2010-10-23 16:35 ` Eric Dumazet
2010-10-23 17:37 ` "Oleg A. Arkhangelsky"
2010-10-23 19:44 ` Eric Dumazet
2010-10-26 18:43 ` David Miller
2010-10-26 13:29 ` Joe Buehler [this message]
2010-10-26 13:36 ` Eric Dumazet
2010-10-26 13:53 ` Joe Buehler
2010-10-26 13:58 ` Eric Dumazet
2010-10-26 14:33 ` Eric Dumazet
2010-10-26 14:41 ` Joe Buehler
2010-10-27 21:01 ` Joe Buehler
2010-10-27 21:05 ` Eric Dumazet
2010-12-02 13:36 ` Joe Buehler
2010-12-02 14:04 ` Eric Dumazet
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