From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: linuxppc-dev@ozlabs.org, akpm@linux-foundation.org,
torvalds@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] synchronize_irq needs a barrier
Date: Fri, 19 Oct 2007 07:35:05 +1000 [thread overview]
Message-ID: <1192743305.7367.11.camel@pasglop> (raw)
In-Reply-To: <E1IiWTY-0000jx-00@gondolin.me.apana.org.au>
On Thu, 2007-10-18 at 22:35 +0800, Herbert Xu wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >
> > Note that some kind of read barrier or compiler barrier should be needed
> > regardless, or we are just not sync'ing with anything at all (we may
> > have loaded the value ages ago and thus operate on a totally stale
> > value). I prefer a full barrier to also ensure all previous stores are
> > pushed out.
>
> We already have a compiler barrier there in the form of cpu_relax.
Isn't it too late ? The barrier should be before the test_bit, to
prevent it from moving up.
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] synchronize_irq needs a barrier
Date: Fri, 19 Oct 2007 07:35:05 +1000 [thread overview]
Message-ID: <1192743305.7367.11.camel@pasglop> (raw)
In-Reply-To: <E1IiWTY-0000jx-00@gondolin.me.apana.org.au>
On Thu, 2007-10-18 at 22:35 +0800, Herbert Xu wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >
> > Note that some kind of read barrier or compiler barrier should be needed
> > regardless, or we are just not sync'ing with anything at all (we may
> > have loaded the value ages ago and thus operate on a totally stale
> > value). I prefer a full barrier to also ensure all previous stores are
> > pushed out.
>
> We already have a compiler barrier there in the form of cpu_relax.
Isn't it too late ? The barrier should be before the test_bit, to
prevent it from moving up.
Ben.
next prev parent reply other threads:[~2007-10-18 21:35 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-18 1:25 [PATCH] synchronize_irq needs a barrier Benjamin Herrenschmidt
2007-10-18 1:25 ` Benjamin Herrenschmidt
2007-10-18 1:45 ` Andrew Morton
2007-10-18 1:45 ` Andrew Morton
2007-10-18 1:55 ` Benjamin Herrenschmidt
2007-10-18 1:55 ` Benjamin Herrenschmidt
2007-10-18 2:12 ` Linus Torvalds
2007-10-18 2:12 ` Linus Torvalds
2007-10-18 2:40 ` Benjamin Herrenschmidt
2007-10-18 2:40 ` Benjamin Herrenschmidt
2007-10-18 2:57 ` Benjamin Herrenschmidt
2007-10-18 2:57 ` Benjamin Herrenschmidt
2007-10-18 14:56 ` Herbert Xu
2007-10-18 14:56 ` Herbert Xu
2007-10-18 22:05 ` Benjamin Herrenschmidt
2007-10-18 22:05 ` Benjamin Herrenschmidt
2007-10-18 22:52 ` Linus Torvalds
2007-10-18 22:52 ` Linus Torvalds
2007-10-18 23:17 ` Benjamin Herrenschmidt
2007-10-18 23:17 ` Benjamin Herrenschmidt
2007-10-18 23:39 ` Linus Torvalds
2007-10-18 23:39 ` Linus Torvalds
2007-10-18 23:52 ` Benjamin Herrenschmidt
2007-10-18 23:52 ` Benjamin Herrenschmidt
2007-10-19 2:32 ` Herbert Xu
2007-10-19 2:32 ` Herbert Xu
2007-10-19 2:52 ` Nick Piggin
2007-10-19 2:52 ` Nick Piggin
2007-10-19 3:28 ` Herbert Xu
2007-10-19 3:28 ` Herbert Xu
2007-10-19 4:49 ` Nick Piggin
2007-10-19 4:49 ` Nick Piggin
2007-10-19 2:55 ` Linus Torvalds
2007-10-19 2:55 ` Linus Torvalds
2007-10-19 3:26 ` Linus Torvalds
2007-10-19 3:26 ` Linus Torvalds
2007-10-19 4:11 ` Benjamin Herrenschmidt
2007-10-19 4:11 ` Benjamin Herrenschmidt
2007-10-19 4:26 ` Benjamin Herrenschmidt
2007-10-19 4:26 ` Benjamin Herrenschmidt
2007-10-19 5:53 ` Herbert Xu
2007-10-19 5:53 ` Herbert Xu
2007-10-19 4:20 ` Herbert Xu
2007-10-19 4:20 ` Herbert Xu
2007-10-19 4:29 ` Benjamin Herrenschmidt
2007-10-19 4:29 ` Benjamin Herrenschmidt
2007-10-19 4:35 ` Benjamin Herrenschmidt
2007-10-19 4:35 ` Benjamin Herrenschmidt
2007-10-19 4:48 ` Herbert Xu
2007-10-19 4:48 ` Herbert Xu
2007-10-19 4:58 ` Benjamin Herrenschmidt
2007-10-19 4:58 ` Benjamin Herrenschmidt
2007-10-21 21:10 ` Benjamin Herrenschmidt
2007-10-21 21:10 ` Benjamin Herrenschmidt
2007-10-23 3:26 ` [IRQ]: Fix synchronize_irq races with IRQ handler Herbert Xu
2007-10-23 3:26 ` Herbert Xu
2007-10-19 5:36 ` [NET]: Fix possible dev_deactivate race condition Herbert Xu
2007-10-19 5:36 ` Herbert Xu
2007-10-19 5:38 ` David Miller
2007-10-19 5:38 ` David Miller
2007-10-19 7:35 ` Peter Zijlstra
2007-10-19 7:35 ` Peter Zijlstra
2007-10-19 9:29 ` Herbert Xu
2007-10-19 9:29 ` Herbert Xu
2007-10-18 14:35 ` [PATCH] synchronize_irq needs a barrier Herbert Xu
2007-10-18 14:35 ` Herbert Xu
2007-10-18 21:35 ` Benjamin Herrenschmidt [this message]
2007-10-18 21:35 ` Benjamin Herrenschmidt
2007-10-20 2:02 ` Maxim Levitsky
2007-10-20 2:02 ` Maxim Levitsky
2007-10-20 2:25 ` Linus Torvalds
2007-10-20 2:25 ` Linus Torvalds
2007-10-20 3:10 ` Maxim Levitsky
2007-10-20 3:10 ` Maxim Levitsky
2007-10-20 4:06 ` Benjamin Herrenschmidt
2007-10-20 4:06 ` Benjamin Herrenschmidt
2007-10-20 4:04 ` Benjamin Herrenschmidt
2007-10-20 4:04 ` Benjamin Herrenschmidt
2007-10-20 4:09 ` Benjamin Herrenschmidt
2007-10-20 4:09 ` Benjamin Herrenschmidt
2007-10-20 3:37 ` Herbert Xu
2007-10-20 3:37 ` Herbert Xu
2007-10-20 3:56 ` Benjamin Herrenschmidt
2007-10-20 3:56 ` Benjamin Herrenschmidt
2007-10-20 4:24 ` Maxim Levitsky
2007-10-20 4:24 ` Maxim Levitsky
2007-10-20 5:04 ` Benjamin Herrenschmidt
2007-10-20 5:04 ` Benjamin Herrenschmidt
2007-10-20 5:36 ` Maxim Levitsky
2007-10-20 5:36 ` Maxim Levitsky
2007-10-20 5:46 ` Benjamin Herrenschmidt
2007-10-20 5:46 ` Benjamin Herrenschmidt
2007-10-20 6:06 ` Maxim Levitsky
2007-10-20 6:06 ` Maxim Levitsky
2007-10-20 6:13 ` Benjamin Herrenschmidt
2007-10-20 6:13 ` Benjamin Herrenschmidt
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