Date: Wed, 22 Oct 2014 16:02:07 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        Robert Richter <rric@kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Mike Galbraith <efault@gmx.de>, Paul Mackerras <paulus@samba.org>,
        Stephane Eranian <eranian@google.com>, Andi Kleen <ak@linux.intel.com>,
        kan.liang@intel.com, adrian.hunter@intel.com, acme@infradead.org
Subject: Re: [PATCH v5 07/20] perf: Add api for pmus to write to AUX area
Message-ID: <20141022140207.GN12706@worktop.programming.kicks-ass.net>
References: <1413207948-28202-1-git-send-email-alexander.shishkin@linux.intel.com>
 <1413207948-28202-8-git-send-email-alexander.shishkin@linux.intel.com>
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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.
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