linux-kernel - Re: [PATCH 1/7] perf_counter: fix dynamic irq

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Message-ID: <18969.57730.876306.394502@cargo.ozlabs.ibm.com>
Date:	Mon, 25 May 2009 10:08:34 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	John Kacur <jkacur@...hat.com>
Subject: Re: [PATCH 1/7] perf_counter: fix dynamic irq_period logging

Peter Zijlstra writes:

> We call perf_adjust_freq() from perf_counter_task_tick() which is is called
> under the rq->lock causing lock recursion.

What was the lock recursion?  I see perf_adjust_freq taking ctx->lock,
but we were careful not to take any rq->lock within a ctx->lock, at
least in the past.

Paul.
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