linux-kernel - RE: [PATCH V2] smp: Give WARN()ing when calling smp_call_function

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Date:	Wed, 20 Feb 2013 01:22:09 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	"Wu, Fengguang" <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"jbeulich@...e.com" <jbeulich@...e.com>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"mina86@...a86.org" <mina86@...a86.org>,
	"srivatsa.bhat@...ux.vnet.ibm.com" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Zhang, Jun" <jun.zhang@...el.com>
Subject: RE: [PATCH V2] smp: Give WARN()ing when calling
 smp_call_function_many()/single() in serving irq



> -----Original Message-----
> From: Wu, Fengguang
> Sent: Wednesday, February 20, 2013 9:07 AM
> To: Andrew Morton
> Cc: Liu, Chuansheng; mingo@...nel.org; peterz@...radead.org;
> jbeulich@...e.com; paulmck@...ux.vnet.ibm.com; mina86@...a86.org;
> srivatsa.bhat@...ux.vnet.ibm.com; linux-kernel@...r.kernel.org; Zhang, Jun
> Subject: Re: [PATCH V2] smp: Give WARN()ing when calling
> smp_call_function_many()/single() in serving irq
> 
> On Tue, Feb 19, 2013 at 03:01:23PM -0800, Andrew Morton wrote:
> > On Mon, 18 Feb 2013 09:38:52 +0800
> > Fengguang Wu <fengguang.wu@...el.com> wrote:
> >
> > > Chuansheng,
> > >
> > > It works fine on tip/next. Thanks for the fix!
> > >
> > > Tested-by: Fengguang Wu <fengguang.wu@...el.com>
> >
> > How did you test this?  What did you do?
> 
> I used the same kconfig to build a kernel from tip/next HEAD *plus*
> the v2 patch. The result is, no smp_call_function_single/many warnings
> are observed.
> 
> > afacit the patch adds additional warnings, so you must have had some
> > buggy code and with the patch, runtime warnings are generated which
> > inform you of that bug?
> 
> Andrew, the background is: Ingo has *reverted* the original patch that
> triggered the smp_call_function_single warning from his tip tree, so
> the test result means this patch's warning messages won't trigger in
> my test boots.
I also locally tested the below several cases, thanks.
1/ local_bh_disable(), then called smp_call_function_single(), no WARNING;
2/ In timer callback, then called smp_call_function_single(), WARNING;

> 
> Thanks,
> Fengguang
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