From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Peter Zijlstra <peterz@infradead.org>,
Milton Miller <miltonm@bga.com>,
akpm@linux-foundation.org, Anton Blanchard <anton@samba.org>,
xiaoguangrong@cn.fujitsu.com, mingo@elte.hu, jaxboe@fusionio.com,
npiggin@gmail.com, rusty@rustcorp.com.au,
linux-kernel@vger.kernel.org
Subject: Re: call_function_many: fix list delete vs add race
Date: Mon, 31 Jan 2011 20:45:17 -0800 [thread overview]
Message-ID: <20110201044517.GC2158@linux.vnet.ibm.com> (raw)
In-Reply-To: <AANLkTimb7bpTa0fO2VU4pSxO-a3-eQNA6zA_ikAReXsQ@mail.gmail.com>
On Tue, Feb 01, 2011 at 12:43:56PM +1000, Linus Torvalds wrote:
> On Tue, Feb 1, 2011 at 12:18 PM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
> >
> > Documentation/memory-barriers.txt specifies this.
>
> Good, so it really is documented, with both cases explicitly mentioned.
>
> That said, I do think that if your memory ordering is much weaker than
> x86, you are going to see bugs that most testers don't see, and it
> simply might not be worth it.
IBM's CPUs do split the difference, with s390 having somewhat stronger
ordering than x86, and with powerpc being rather weaker (along with arm,
ia64, and some flavors of mips, but stronger than alpha). But yes, this
does mean that there are bugs that don't show up on x86 and s390, but
that do on powerpc, arm, ia64, and some mips, to say nothing of alpha.
Similarly, there are bugs that show up on x86 due to unsynchronized
timestamp counters that powerpc and s390 avoid due to the guaranteed
synchronization on those platforms.
Whether the weaker ordering provides worthwhile benefits is an interesting
debate that I do not believe we will be able to resolve here. ;-)
Thanx, Paul
next prev parent reply other threads:[~2011-02-01 4:45 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-12 4:07 [PATCH] smp_call_function_many SMP race Anton Blanchard
2011-01-17 18:17 ` Peter Zijlstra
2011-01-18 21:05 ` Milton Miller
2011-01-18 21:06 ` [PATCH 2/2] consolidate writes in smp_call_funtion_interrupt Milton Miller
2011-01-27 16:22 ` Peter Zijlstra
2011-01-27 21:59 ` Milton Miller
2011-01-29 0:20 ` call_function_many: fix list delete vs add race Milton Miller
2011-01-31 7:21 ` Mike Galbraith
2011-01-31 20:26 ` [PATCH] smp_call_function_many: handle concurrent clearing of mask Milton Miller
2011-02-01 3:15 ` Mike Galbraith
2011-01-31 10:27 ` call_function_many: fix list delete vs add race Peter Zijlstra
2011-01-31 20:26 ` Milton Miller
2011-01-31 20:39 ` Peter Zijlstra
2011-01-31 21:17 ` Peter Zijlstra
2011-01-31 21:36 ` Milton Miller
2011-02-01 0:22 ` Benjamin Herrenschmidt
2011-02-01 1:39 ` Linus Torvalds
2011-02-01 2:18 ` Paul E. McKenney
2011-02-01 2:43 ` Linus Torvalds
2011-02-01 4:45 ` Paul E. McKenney [this message]
2011-02-01 5:46 ` Linus Torvalds
2011-02-01 6:18 ` Benjamin Herrenschmidt
2011-02-01 14:13 ` Paul E. McKenney
2011-02-01 6:16 ` Benjamin Herrenschmidt
[not found] ` <ipi-list-reply@mdm.bga.com>
2011-02-01 7:12 ` [PATCH 1/3 v2] " Milton Miller
2011-02-01 22:00 ` Paul E. McKenney
2011-02-01 22:00 ` Milton Miller
2011-02-02 4:17 ` Paul E. McKenney
2011-02-06 23:51 ` Paul E. McKenney
2011-03-15 19:27 ` [PATCH 0/4 v3] smp_call_function_many issues from review Milton Miller
2011-03-15 20:22 ` Luck, Tony
2011-03-15 20:32 ` Dimitri Sivanich
2011-03-15 20:39 ` Peter Zijlstra
2011-03-16 17:55 ` Linus Torvalds
2011-03-16 18:13 ` Peter Zijlstra
2011-03-17 3:15 ` Mike Galbraith
2011-02-07 8:12 ` [PATCH 1/3 v2] call_function_many: fix list delete vs add race Mike Galbraith
2011-02-08 19:36 ` Paul E. McKenney
2011-08-21 6:17 ` Mike Galbraith
2011-02-02 6:22 ` Mike Galbraith
2011-02-01 7:12 ` [PATCH 2/3 v2] smp_call_function_many: handle concurrent clearing of mask Milton Miller
2011-03-15 19:27 ` [PATCH 2/4 v3] call_function_many: add missing ordering Milton Miller
2011-03-16 12:06 ` Paul E. McKenney
2011-03-15 19:27 ` [PATCH 1/4 v3] call_function_many: fix list delete vs add race Milton Miller
2011-03-15 19:27 ` [PATCH 4/4 v3] smp_call_function_interrupt: use typedef and %pf Milton Miller
2011-03-15 19:27 ` [PATCH 3/4 v3] smp_call_function_many: handle concurrent clearing of mask Milton Miller
2011-03-15 22:32 ` Catalin Marinas
2011-03-16 7:52 ` Jan Beulich
2011-01-18 21:07 ` [PATCH 1/2] smp_call_function_many SMP race Milton Miller
2011-01-20 0:41 ` Andrew Morton
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