From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>,
"Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
Yinghai Lu <yinghai@kernel.org>, Nick Piggin <npiggin@suse.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Jens Axboe <jens.axboe@oracle.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: Q: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many())
Date: Wed, 18 Feb 2009 18:05:17 +0100 [thread overview]
Message-ID: <20090218170517.GA9769@elte.hu> (raw)
In-Reply-To: <20090218165808.GA9120@elte.hu>
an off-list comment pointed out this piece of information as
well:
http://www.sandpile.org/ia32/coherent.htm
A WRMSR to one of the x2APIC MSRs (0000_0800h...0000_0BFFh) is
not guaranteed to be serializing.
So i suspect we should just enclose it in smp_mb() pairs to make
sure it's a full barrier in both directions?
Although since it's an explicitly async mechanism with no
ordering expectations whatsoever, just doing an smp_mb() before
it should be enough, to make sure the IPI can never arrive to
another CPU/core faster than the event-horizon/visibility of
preceding operations.
Ingo
next prev parent reply other threads:[~2009-02-18 17:05 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-16 16:38 [PATCH 0/4] generic smp helpers vs kmalloc Peter Zijlstra
2009-02-16 16:38 ` [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many() Peter Zijlstra
2009-02-16 19:10 ` Oleg Nesterov
2009-02-16 19:41 ` Peter Zijlstra
2009-02-16 20:30 ` Oleg Nesterov
2009-02-16 20:55 ` Peter Zijlstra
2009-02-16 21:22 ` Oleg Nesterov
2009-02-17 12:25 ` Oleg Nesterov
2009-02-16 20:49 ` Q: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many()) Oleg Nesterov
2009-02-16 21:03 ` Peter Zijlstra
2009-02-16 21:32 ` Oleg Nesterov
2009-02-16 21:45 ` Peter Zijlstra
2009-02-16 22:02 ` Oleg Nesterov
2009-02-16 22:24 ` Peter Zijlstra
2009-02-16 23:19 ` Oleg Nesterov
2009-02-17 9:29 ` Peter Zijlstra
2009-02-17 10:11 ` Nick Piggin
2009-02-17 10:27 ` Peter Zijlstra
2009-02-17 10:39 ` Nick Piggin
2009-02-17 11:26 ` Nick Piggin
2009-02-17 11:48 ` Peter Zijlstra
2009-02-17 15:51 ` Paul E. McKenney
2009-02-18 2:15 ` Suresh Siddha
2009-02-18 2:40 ` Paul E. McKenney
2009-02-17 19:28 ` Q: " Oleg Nesterov
2009-02-17 21:32 ` Paul E. McKenney
2009-02-17 21:45 ` Oleg Nesterov
2009-02-17 22:39 ` Paul E. McKenney
2009-02-18 13:52 ` Nick Piggin
2009-02-18 16:09 ` Linus Torvalds
2009-02-18 16:21 ` Ingo Molnar
2009-02-18 16:21 ` Ingo Molnar
2009-02-18 16:21 ` Ingo Molnar
2009-02-18 16:33 ` Linus Torvalds
2009-02-18 16:58 ` Ingo Molnar
2009-02-18 17:05 ` Ingo Molnar [this message]
2009-02-18 17:10 ` Ingo Molnar
2009-02-18 17:17 ` Linus Torvalds
2009-02-18 17:23 ` Ingo Molnar
2009-02-18 17:14 ` Linus Torvalds
2009-02-18 17:47 ` Ingo Molnar
2009-02-18 18:33 ` Suresh Siddha
2009-02-18 16:37 ` Gleb Natapov
2009-02-19 0:12 ` Nick Piggin
2009-02-19 6:47 ` Benjamin Herrenschmidt
2009-02-19 13:11 ` Nick Piggin
2009-02-19 15:06 ` Ingo Molnar
2009-02-19 21:49 ` Benjamin Herrenschmidt
2009-02-18 2:21 ` Suresh Siddha
2009-02-18 13:59 ` Nick Piggin
2009-02-18 16:19 ` Linus Torvalds
2009-02-18 16:23 ` Ingo Molnar
2009-02-18 18:43 ` Suresh Siddha
2009-02-18 19:17 ` Ingo Molnar
2009-02-18 23:55 ` Suresh Siddha
2009-02-19 12:20 ` Ingo Molnar
2009-02-19 12:29 ` Nick Piggin
2009-02-19 12:45 ` Ingo Molnar
2009-02-19 22:00 ` Suresh Siddha
2009-02-20 10:56 ` Ingo Molnar
2009-02-20 18:56 ` Suresh Siddha
2009-02-20 19:40 ` Ingo Molnar
2009-02-20 23:28 ` Jack Steiner
2009-02-25 3:32 ` Nick Piggin
2009-02-25 12:47 ` Ingo Molnar
2009-02-25 18:25 ` Luck, Tony
2009-03-17 18:16 ` Suresh Siddha
2009-03-18 8:51 ` [tip:x86/x2apic] x86: add x2apic_wrmsr_fence() to x2apic flush tlb paths Suresh Siddha
2009-02-17 12:40 ` Q: smp.c && barriers (Was: [PATCH 1/4] generic-smp: remove single ipi fallback for smp_call_function_many()) Peter Zijlstra
2009-02-17 15:43 ` Paul E. McKenney
2009-02-17 15:40 ` [PATCH] generic-smp: remove kmalloc() Peter Zijlstra
2009-02-17 17:21 ` Oleg Nesterov
2009-02-17 17:40 ` Peter Zijlstra
2009-02-17 17:46 ` Peter Zijlstra
2009-02-17 18:30 ` Oleg Nesterov
2009-02-17 19:29 ` [PATCH -v4] generic-ipi: " Peter Zijlstra
2009-02-17 20:02 ` Oleg Nesterov
2009-02-17 20:11 ` Peter Zijlstra
2009-02-17 20:16 ` Peter Zijlstra
2009-02-17 20:44 ` Oleg Nesterov
2009-02-17 20:49 ` Peter Zijlstra
2009-02-17 22:09 ` Oleg Nesterov
2009-02-17 22:15 ` Peter Zijlstra
2009-02-17 21:30 ` Paul E. McKenney
2009-02-17 21:38 ` Peter Zijlstra
2009-02-16 16:38 ` [PATCH 2/4] generic-smp: remove kmalloc usage Peter Zijlstra
2009-02-17 0:40 ` Linus Torvalds
2009-02-17 8:24 ` Peter Zijlstra
2009-02-17 9:43 ` Ingo Molnar
2009-02-17 9:49 ` Peter Zijlstra
2009-02-17 10:56 ` Ingo Molnar
2009-02-18 4:50 ` Rusty Russell
2009-02-18 16:05 ` Ingo Molnar
2009-02-19 0:00 ` Jeremy Fitzhardinge
2009-02-19 12:21 ` Ingo Molnar
2009-02-19 4:31 ` Rusty Russell
2009-02-19 9:10 ` Peter Zijlstra
2009-02-19 11:04 ` Jens Axboe
2009-02-19 16:52 ` Linus Torvalds
2009-02-17 15:44 ` Linus Torvalds
2009-02-16 16:38 ` [PATCH 3/4] generic-smp: properly allocate the cpumasks Peter Zijlstra
2009-02-16 23:17 ` Rusty Russell
2009-02-16 16:38 ` [PATCH 4/4] generic-smp: clean up some of the csd->flags fiddling Peter Zijlstra
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