From: Linus Torvalds <torvalds@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Rusty Russell <rusty@rustcorp.com.au>,
npiggin@suse.de, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@infradead.org>,
jens.axboe@oracle.com
Subject: Re: [PATCH -v2] use per cpu data for single cpu ipi calls
Date: Thu, 29 Jan 2009 10:08:23 -0800 (PST) [thread overview]
Message-ID: <alpine.LFD.2.00.0901290959540.3123@localhost.localdomain> (raw)
In-Reply-To: <alpine.DEB.1.10.0901291232570.27527@gandalf.stny.rr.com>
On Thu, 29 Jan 2009, Steven Rostedt wrote:
>
> Actually, we are locking against the destination CPU.
Oh.
THAT'S JUST INCOMPETENT.
What the *fuck* is the point of having per-CPU data, and then using it for
the wrong CPU?
Stop doing that idiocy. Put the per-cpu data on the senders side, and stop
the idiocy. You are going to get cross-CPU cacheline bouncing anyway,
there's no way to avoid it, but as long as you do it on the wrong CPU's
local data, you're missing the whole POINT of having per-cpu data in the
first place.
But yeah, that explains the locking. One stupid design mistake leads to
another.
And are you really sure it cannot be called from within interrupts? I'm
finding a lot of callers of smp_call_function_single(), and while I
couldn't find any that look like interrupts, I also couldn't find any
indication that it never happens.
Linus
next prev parent reply other threads:[~2009-01-29 18:09 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-28 16:38 Buggy IPI and MTRR code on low memory Steven Rostedt
2009-01-28 16:41 ` Steven Rostedt
2009-01-28 16:46 ` Peter Zijlstra
2009-01-28 16:56 ` Steven Rostedt
2009-01-28 17:00 ` Peter Zijlstra
2009-01-28 17:24 ` Steven Rostedt
2009-01-28 18:20 ` Peter Zijlstra
2009-01-28 18:52 ` Steven Rostedt
2009-01-28 18:22 ` Arjan van de Ven
2009-01-28 18:34 ` Steven Rostedt
2009-01-28 21:12 ` Andrew Morton
2009-01-28 21:13 ` Andrew Morton
2009-01-28 21:23 ` Steven Rostedt
2009-01-28 22:07 ` Andrew Morton
2009-01-28 22:47 ` Steven Rostedt
2009-01-28 23:20 ` Andrew Morton
2009-01-28 23:50 ` Steven Rostedt
2009-01-28 23:25 ` Rusty Russell
2009-01-28 23:41 ` Steven Rostedt
2009-01-29 0:52 ` [PATCH] use per cpu data for single cpu ipi calls Steven Rostedt
2009-01-29 1:30 ` Andrew Morton
2009-01-29 1:56 ` Steven Rostedt
2009-01-29 8:49 ` Peter Zijlstra
2009-01-29 11:13 ` Ingo Molnar
2009-01-29 11:41 ` Peter Zijlstra
2009-01-29 13:42 ` Ingo Molnar
2009-01-29 14:07 ` Steven Rostedt
2009-01-29 15:08 ` [PATCH -v2] " Steven Rostedt
2009-01-29 15:33 ` Peter Zijlstra
2009-01-29 16:17 ` Ingo Molnar
2009-01-29 17:21 ` Linus Torvalds
2009-01-29 17:44 ` Steven Rostedt
2009-01-29 17:50 ` Steven Rostedt
2009-01-29 18:08 ` Linus Torvalds [this message]
2009-01-29 18:11 ` Steven Rostedt
2009-01-29 18:23 ` Peter Zijlstra
2009-01-29 18:31 ` Steven Rostedt
2009-01-29 18:39 ` Linus Torvalds
2009-01-29 18:44 ` Peter Zijlstra
2009-01-30 11:23 ` Jens Axboe
2009-01-30 12:32 ` [PATCH -v3] " Peter Zijlstra
2009-01-30 12:38 ` Jens Axboe
2009-01-30 12:48 ` Peter Zijlstra
2009-01-30 12:55 ` Jens Axboe
2009-01-30 12:56 ` Jens Axboe
2009-01-30 13:00 ` Peter Zijlstra
2009-01-30 13:02 ` [PATCH -v4] " Peter Zijlstra
2009-01-30 14:51 ` Ingo Molnar
2009-01-30 16:04 ` [PATCH -v3] " Linus Torvalds
2009-01-30 16:16 ` Peter Zijlstra
2009-01-31 8:44 ` Jens Axboe
2009-01-29 18:49 ` [PATCH -v2] " Ingo Molnar
2009-01-30 1:55 ` Rusty Russell
2009-01-29 17:47 ` Peter Zijlstra
2009-01-29 17:55 ` Peter Zijlstra
2009-01-29 18:08 ` Steven Rostedt
2009-01-30 1:11 ` Rusty Russell
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