linux-kernel - Re: [PATCH v5 07/20] perf: Add api for pmus to write to AUX area

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Message-ID: <87iojcdweq.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Wed, 22 Oct 2014 17:14:05 +0300
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Robert Richter <rric@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
	adrian.hunter@...el.com, acme@...radead.org
Subject: Re: [PATCH v5 07/20] perf: Add api for pmus to write to AUX area

Peter Zijlstra <peterz@...radead.org> writes:

> On Mon, Oct 13, 2014 at 04:45:35PM +0300, Alexander Shishkin wrote:
>> +	/*
>> +	 * Nesting is not supported for AUX area, make sure nested
>> +	 * writers are caught early
>> +	 */
>> +	if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))
>> +		goto err_put;
>
> Note that printk() from NMI is prone to making your machine die, not
> that I have a better option though.

Indeed, but if your driver is really attempting nested
perf_aux_output_begin()s, then you had it coming to you anyway.

Regards,
--
Alex
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