From: "David S. Miller" <davem@davemloft.net>
To: akpm@osdl.org
Cc: paulmck@us.ibm.com, oleg@tv-sign.ru, vatsa@in.ibm.com,
linux-kernel@vger.kernel.org, dipankar@in.ibm.com
Subject: Re: [PATCH] Fix RCU race in access of nohz_cpu_mask
Date: Sun, 11 Dec 2005 20:38:09 -0800 (PST) [thread overview]
Message-ID: <20051211.203809.127057416.davem@davemloft.net> (raw)
In-Reply-To: <20051211203226.4deafd59.akpm@osdl.org>
From: Andrew Morton <akpm@osdl.org>
Date: Sun, 11 Dec 2005 20:32:26 -0800
> So foo_mb() in preemptible code is potentially buggy.
>
> I guess we assume that a context switch accidentally did enough of the
> right types of barriers for things to work OK.
A trap ought to flush all memory operations.
There are some incredibly difficult memory error handling cases if the
cpu does not synchronize all pending memory operations when a trap
occurs.
Failing that, yes, to be absolutely safe we'd need to have some
explicit memory barrier in the context switch.
next prev parent reply other threads:[~2005-12-12 4:38 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-08 19:31 Oleg Nesterov
2005-12-09 2:46 ` Srivatsa Vaddagiri
2005-12-09 19:17 ` Oleg Nesterov
2005-12-10 15:19 ` Srivatsa Vaddagiri
2005-12-10 18:55 ` Oleg Nesterov
2005-12-11 17:41 ` Semantics of smp_mb() [was : Re: [PATCH] Fix RCU race in access of nohz_cpu_mask ] Srivatsa Vaddagiri
2005-12-11 21:21 ` Andrew James Wade
2005-12-11 23:45 ` Rusty Russell
2005-12-12 0:49 ` Keith Owens
2005-12-12 8:41 ` Srivatsa Vaddagiri
2005-12-12 19:33 ` Oleg Nesterov
2005-12-13 5:20 ` Paul E. McKenney
2005-12-13 5:07 ` Andrew James Wade
2005-12-13 5:43 ` Paul E. McKenney
2005-12-13 11:20 ` Andi Kleen
2005-12-13 16:20 ` Paul E. McKenney
2005-12-13 22:27 ` Keith Owens
2005-12-13 22:50 ` Paul E. McKenney
2005-12-14 1:12 ` Andi Kleen
2005-12-14 1:46 ` Paul E. McKenney
2005-12-15 21:15 ` Semantics of smp_mb() Roland Dreier
2005-12-16 7:46 ` Semantics of smp_mb() [was : Re: [PATCH] Fix RCU race in access of nohz_cpu_mask ] Jeremy Higdon
2006-03-13 18:39 ` Paul E. McKenney
2006-03-31 4:56 ` Jeremy Higdon
2006-03-31 6:18 ` Paul E. McKenney
2006-03-31 23:38 ` Jesse Barnes
2005-12-12 3:10 ` [PATCH] Fix RCU race in access of nohz_cpu_mask Paul E. McKenney
2005-12-12 4:32 ` Andrew Morton
2005-12-12 4:38 ` David S. Miller [this message]
2005-12-12 4:47 ` Nick Piggin
2005-12-12 4:49 ` Paul Mackerras
2005-12-12 6:27 ` Keith Owens
2005-12-09 2:56 ` Srivatsa Vaddagiri
-- strict thread matches above, loose matches on Subject: below --
2005-12-05 11:02 Srivatsa Vaddagiri
2005-12-08 0:37 ` Andrew Morton
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