From: Andi Kleen <andi@firstfloor.org>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
"Mallick, Asit K" <asit.k.mallick@intel.com>
Subject: Re: [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask after switching mm
Date: Thu, 3 Feb 2011 03:15:10 +0100 [thread overview]
Message-ID: <20110203021510.GM15569@one.firstfloor.org> (raw)
In-Reply-To: <1296698151.4418.464.camel@sbsiddha-MOBL3.sc.intel.com>
> I thought "asm volatile" is going to take care of that.
asm volatile just prevents deletion:
>>
The `volatile' keyword indicates that the instruction has important
side-effects. GCC will not delete a volatile `asm' if it is reachable.
(The instruction can still be deleted if GCC can prove that
control-flow will never reach the location of the instruction.) Note
that even a volatile `asm' instruction can be moved relative to other
code, including across jump instructions.
<<
> If not, then we have issues even today. no?
Well yes. It depends on the compiler if it actually moves something.
So most likely nothing was reordered yet, but it's safer to prevent
it.
I normally go by the rule that if correctness requires a specific
order without explicit side effects I add memory barriers.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2011-02-03 2:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-02 20:07 [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask after switching mm Suresh Siddha
2011-02-03 1:23 ` Andi Kleen
2011-02-03 1:55 ` Suresh Siddha
2011-02-03 2:15 ` Andi Kleen [this message]
2011-02-03 4:12 ` Linus Torvalds
2011-02-03 4:22 ` H. Peter Anvin
2011-02-03 1:55 ` Linus Torvalds
2011-02-03 4:03 ` Linus Torvalds
2011-02-03 18:27 ` Suresh Siddha
2011-02-03 19:13 ` Linus Torvalds
2011-02-03 19:34 ` Suresh Siddha
2011-02-03 19:48 ` Linus Torvalds
2011-02-03 20:20 ` Suresh Siddha
2011-02-03 21:06 ` Ingo Molnar
2011-02-03 21:33 ` Linus Torvalds
2011-02-03 21:39 ` Ingo Molnar
[not found] <BLU157-w495F35A445E063E33DC9E8DAAC0@phx.gbl>
[not found] ` <BLU157-w41A610FD3413183801060CDAAC0@phx.gbl>
[not found] ` <BLU157-w548B9D2F8EDD8CA9DB6CD3DAAC0@phx.gbl>
2011-04-15 11:58 ` MaoXiaoyun
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