linux-kernel - Re: [linux-next][regression] [PATCH] percpu: add preemption checks to __this

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Message-ID: <alpine.DEB.2.10.1403200905070.4107@nuc>
Date:	Thu, 20 Mar 2014 09:06:34 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Grygorii Strashko <grygorii.strashko@...com>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [linux-next][regression] [PATCH] percpu: add preemption checks
 to __this_cpu ops

On Tue, 18 Mar 2014, Andrew Morton wrote:

> > snprintf can cause hangs.
>
> This is weird.  How the heck can snprintf() fail if called too early?
> All it does is shuffle chars around in memory.  The only external
> dependency I'm seeing is a WARN_ON() which presumably didn't trigger
> anyway.
>
> I'm suspecting a misdiagnosis here.  Otherwise, we seriously need to
> fix snprintf(), not work around it!
>
> Also, what does "before checking error conditions" refer to?  Does this
> mean you know why snprintf() failed??

No I dont. I only know that this fixes Grygorii's issues. There could be
numerous arch specific per cpu setup issues going on that may impact on
snprintf.

If I move it behind the checks then I can avoid using snprintf.
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