From: Peter Zijlstra <peterz@infradead•org>
To: "Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
Cc: Michael Neuling <mikey@neuling•org>,
Mathieu Desnoyers <mathieu.desnoyers@polymtl•ca>,
Oleg Nesterov <oleg@redhat•com>,
LKML <linux-kernel@vger•kernel.org>,
Linux PPC dev <linuxppc-dev@ozlabs•org>,
Anton Blanchard <anton@samba•org>,
Frederic Weisbecker <fweisbec@gmail•com>,
Victor Kaplansky <VICTORK@il•ibm.com>
Subject: Re: perf events ring buffer memory barrier on powerpc
Date: Fri, 1 Nov 2013 17:18:19 +0100 [thread overview]
Message-ID: <20131101161819.GV16117@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <20131031064015.GV4126@linux.vnet.ibm.com>
On Wed, Oct 30, 2013 at 11:40:15PM -0700, Paul E. McKenney wrote:
> The dependency you are talking about is via the "if" statement?
> Even C/C++11 is not required to respect control dependencies.
>
> This one is a bit annoying. The x86 TSO means that you really only
> need barrier(), ARM (recent ARM, anyway) and Power could use a weaker
> barrier, and so on -- but smp_mb() emits a full barrier.
>
> Perhaps a new smp_tmb() for TSO semantics, where reads are ordered
> before reads, writes before writes, and reads before writes, but not
> writes before reads? Another approach would be to define a per-arch
> barrier for this particular case.
Supposing a sane language where we can rely on control flow; would that
change the story?
I'm afraid I'm now terminally confused between actual proper memory
model issues and fucked compilers.
next prev parent reply other threads:[~2013-11-01 16:18 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-22 23:54 perf events ring buffer memory barrier on powerpc Michael Neuling
2013-10-23 7:39 ` Victor Kaplansky
2013-10-23 14:19 ` Frederic Weisbecker
2013-10-23 14:25 ` Frederic Weisbecker
2013-10-25 17:37 ` Peter Zijlstra
2013-10-25 20:31 ` Michael Neuling
2013-10-27 9:00 ` Victor Kaplansky
2013-10-28 9:22 ` Peter Zijlstra
2013-10-28 10:02 ` Frederic Weisbecker
2013-10-28 12:38 ` Victor Kaplansky
2013-10-28 13:26 ` Peter Zijlstra
2013-10-28 16:34 ` Paul E. McKenney
2013-10-28 20:17 ` Oleg Nesterov
2013-10-28 20:58 ` Victor Kaplansky
2013-10-29 10:21 ` Peter Zijlstra
2013-10-29 10:30 ` Peter Zijlstra
2013-10-29 10:35 ` Peter Zijlstra
2013-10-29 20:15 ` Oleg Nesterov
2013-10-29 19:27 ` Vince Weaver
2013-10-30 10:42 ` Peter Zijlstra
2013-10-30 11:48 ` James Hogan
2013-10-30 12:48 ` Peter Zijlstra
2013-10-29 21:23 ` Michael Neuling
2013-10-30 9:27 ` Paul E. McKenney
2013-10-30 11:25 ` Peter Zijlstra
2013-10-30 14:52 ` Victor Kaplansky
2013-10-30 15:39 ` Peter Zijlstra
2013-10-30 17:14 ` Victor Kaplansky
2013-10-30 17:44 ` Peter Zijlstra
2013-10-31 6:16 ` Paul E. McKenney
2013-11-01 13:12 ` Victor Kaplansky
2013-11-02 16:36 ` Paul E. McKenney
2013-11-02 17:26 ` Paul E. McKenney
2013-10-31 6:40 ` Paul E. McKenney
2013-11-01 14:25 ` Victor Kaplansky
2013-11-02 17:28 ` Paul E. McKenney
2013-11-01 14:56 ` Peter Zijlstra
2013-11-02 17:32 ` Paul E. McKenney
2013-11-03 14:40 ` Paul E. McKenney
2013-11-03 15:17 ` [RFC] arch: Introduce new TSO memory barrier smp_tmb() Peter Zijlstra
2013-11-03 18:08 ` Linus Torvalds
2013-11-03 20:01 ` Peter Zijlstra
2013-11-03 22:42 ` Paul E. McKenney
2013-11-03 23:34 ` Linus Torvalds
2013-11-04 10:51 ` Paul E. McKenney
2013-11-04 11:22 ` Peter Zijlstra
2013-11-04 16:27 ` Paul E. McKenney
2013-11-04 16:48 ` Peter Zijlstra
2013-11-04 19:11 ` Peter Zijlstra
2013-11-04 19:18 ` Peter Zijlstra
2013-11-04 20:54 ` Paul E. McKenney
2013-11-04 20:53 ` Paul E. McKenney
2013-11-05 14:05 ` Will Deacon
2013-11-05 14:49 ` Paul E. McKenney
2013-11-05 18:49 ` Peter Zijlstra
2013-11-06 11:00 ` Will Deacon
2013-11-06 12:39 ` Peter Zijlstra
2013-11-06 12:51 ` Geert Uytterhoeven
2013-11-06 13:57 ` Peter Zijlstra
2013-11-06 18:48 ` Paul E. McKenney
2013-11-06 19:42 ` Peter Zijlstra
2013-11-07 11:17 ` Will Deacon
2013-11-07 13:36 ` Peter Zijlstra
2013-11-07 23:50 ` Mathieu Desnoyers
2013-11-04 11:05 ` Will Deacon
2013-11-04 16:34 ` Paul E. McKenney
2013-11-03 20:59 ` Benjamin Herrenschmidt
2013-11-03 22:43 ` Paul E. McKenney
2013-11-01 16:11 ` perf events ring buffer memory barrier on powerpc Peter Zijlstra
2013-11-02 17:46 ` Paul E. McKenney
2013-11-01 16:18 ` Peter Zijlstra [this message]
2013-11-02 17:49 ` Paul E. McKenney
2013-10-30 13:28 ` Victor Kaplansky
2013-10-30 15:51 ` Peter Zijlstra
2013-10-30 18:29 ` Peter Zijlstra
2013-10-30 19:11 ` Peter Zijlstra
2013-10-31 4:33 ` Paul E. McKenney
2013-10-31 4:32 ` Paul E. McKenney
2013-10-31 9:04 ` Peter Zijlstra
2013-10-31 15:07 ` Paul E. McKenney
2013-10-31 15:19 ` Peter Zijlstra
2013-11-01 9:28 ` Paul E. McKenney
2013-11-01 10:30 ` Peter Zijlstra
2013-11-02 15:20 ` Paul E. McKenney
2013-11-04 9:07 ` Peter Zijlstra
2013-11-04 10:00 ` Paul E. McKenney
2013-10-31 9:59 ` Victor Kaplansky
2013-10-31 12:28 ` David Laight
2013-10-31 12:55 ` Victor Kaplansky
2013-10-31 15:25 ` Paul E. McKenney
2013-11-01 16:06 ` Victor Kaplansky
2013-11-01 16:25 ` David Laight
2013-11-01 16:30 ` Victor Kaplansky
2013-11-03 20:57 ` Benjamin Herrenschmidt
2013-11-02 15:46 ` Paul E. McKenney
2013-10-28 19:09 ` Oleg Nesterov
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