linux-kernel - Re: [PATCH v1 1/6] perf: Disable PMU around address filter adjustment

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Message-ID: <20180612201127.GW12217@hirez.programming.kicks-ass.net>
Date:   Tue, 12 Jun 2018 22:11:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        linux-kernel@...r.kernel.org, jolsa@...hat.com
Subject: Re: [PATCH v1 1/6] perf: Disable PMU around address filter adjustment

On Tue, Jun 12, 2018 at 10:51:12AM +0300, Alexander Shishkin wrote:
> If the PMU is used for AUX data sampling, the hardware event that triggers
> it may come in during a critical section of address filters adjustment (if
> it's delivered as NMI) and in turn call the address filter sync code,
> causing a spinlock recursion.

Can you detail that a little more? How can sampling _ever_ get down that
path?