From: Thomas Gleixner <tglx@linutronix.de>
To: Christoph Lameter <cl@gentwo.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Christoph Lameter <cl@linux.com>, Tejun Heo <htejun@gmail.com>
Subject: Re: [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu_read()
Date: Tue, 20 Sep 2011 17:27:22 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.02.1109201703560.2723@ionos> (raw)
In-Reply-To: <alpine.DEB.2.00.1109200947100.8056@router.home>
On Tue, 20 Sep 2011, Christoph Lameter wrote:
> On Tue, 20 Sep 2011, Thomas Gleixner wrote:
> > This allows us to do proper analysis of this_cpu usage and makes the
> > code understandable.
>
> Not sure what you want to check in this_cpu_xx operations. Why could
> there be issues with this_cpu_xx operations?
I want to get rid of them alltogether. They are crap by design and
prone to be used wrong without a sensible way to detect that.
> I see that __this_cpu_xx operations may not work as intended in
> preemptable contexts and there we could have more changes.
>
> this_cpu ops are single instructions that do not guarantee any consistency
> with other this_cpu_ops. If you want consistency (same per cpu area data)
> then preemption needs to be disabled.
Right, and that's the main problem. We have no fricking way to debug
this, so they should have never been there in the first place. And you
simply CANNOT prevent people from getting this wrong w/o proper
debugging and annotation. Even YOU and Tejun made bogus conversion w/o
noticing, but you expect that others get it right?
So stop defending that trainwreck and help out with fixing the mess
you created in a proper and debugable way!
Thanks,
tglx
next prev parent reply other threads:[~2011-09-20 15:27 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 21:20 [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 1/5] x86: Remove const_udelay() caring about which cpu var it uses Steven Rostedt
2011-09-19 21:51 ` Christoph Lameter
2011-09-19 23:31 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu_read() Steven Rostedt
2011-09-19 22:02 ` Christoph Lameter
2011-09-19 23:48 ` Steven Rostedt
2011-09-20 14:46 ` Christoph Lameter
2011-09-20 15:16 ` Steven Rostedt
2011-09-20 15:54 ` Christoph Lameter
2011-09-20 16:07 ` Steven Rostedt
2011-09-20 22:19 ` Valdis.Kletnieks
2011-09-20 13:49 ` Thomas Gleixner
2011-09-20 14:01 ` Steven Rostedt
2011-09-20 14:51 ` Christoph Lameter
2011-09-20 15:11 ` Steven Rostedt
2011-09-20 15:59 ` Christoph Lameter
2011-09-20 16:03 ` Steven Rostedt
2011-09-20 16:07 ` Christoph Lameter
2011-09-20 15:27 ` Thomas Gleixner [this message]
2011-09-20 16:02 ` Christoph Lameter
2011-09-20 16:51 ` Thomas Gleixner
2011-09-20 17:08 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 3/5] memcg: Disable preemption in memcg_check_events() Steven Rostedt
2011-09-20 14:20 ` Johannes Weiner
2011-09-20 14:24 ` Johannes Weiner
2011-09-20 14:33 ` Steven Rostedt
2011-09-24 0:46 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 4/5] printk: Have wake_up_klogd() use __this_cpu_write() Steven Rostedt
2011-09-19 21:54 ` Christoph Lameter
2011-09-19 23:33 ` Steven Rostedt
2011-09-20 14:54 ` Christoph Lameter
2011-09-20 14:55 ` Peter Zijlstra
2011-09-19 21:20 ` [RFC][PATCH 5/5] percpu: Add preempt checks back into this_cpu_read/write() Steven Rostedt
2011-09-19 21:49 ` [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Christoph Lameter
2011-09-20 3:06 ` Steven Rostedt
2011-09-20 12:44 ` Valdis.Kletnieks
2011-09-20 13:51 ` Thomas Gleixner
2011-09-20 14:58 ` Christoph Lameter
2011-09-20 15:17 ` Steven Rostedt
2011-09-20 14:57 ` Christoph Lameter
2011-09-20 15:19 ` Steven Rostedt
2011-09-20 16:08 ` Christoph Lameter
2011-09-20 16:31 ` Steven Rostedt
2011-09-20 16:56 ` Steven Rostedt
2011-09-20 17:09 ` Peter Zijlstra
2011-09-20 17:15 ` Steven Rostedt
2011-09-20 17:25 ` Mathieu Desnoyers
2011-09-20 18:03 ` Steven Rostedt
2011-09-20 18:12 ` Mathieu Desnoyers
2011-09-20 18:27 ` Steven Rostedt
2011-09-20 18:34 ` Mathieu Desnoyers
2011-09-20 22:32 ` Valdis.Kletnieks
2011-09-20 22:17 ` Valdis.Kletnieks
2011-09-21 1:33 ` Steven Rostedt
2011-09-20 15:46 ` Mathieu Desnoyers
2011-09-20 16:00 ` Steven Rostedt
2011-09-20 16:10 ` Christoph Lameter
2011-09-20 16:50 ` Peter Zijlstra
2011-09-20 18:54 ` Steven Rostedt
2011-09-21 15:16 ` Christoph Lameter
2011-09-21 15:31 ` Steven Rostedt
2011-09-21 15:59 ` Christoph Lameter
2011-09-21 16:12 ` Steven Rostedt
2011-09-21 16:32 ` Thomas Gleixner
2011-09-20 2:20 ` Andi Kleen
2011-09-20 3:12 ` Steven Rostedt
2011-09-20 3:17 ` Steven Rostedt
2011-09-20 8:32 ` Thomas Gleixner
2011-09-20 12:10 ` Steven Rostedt
2011-09-20 15:03 ` Christoph Lameter
2011-09-20 15:07 ` Peter Zijlstra
2011-09-20 16:05 ` Christoph Lameter
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