linux-kernel - Re: [PATCH v4 2/2] soc: qcom: add l2 cache perf events driver

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Message-ID: <20160902100624.GB9261@leverpostej>
Date:   Fri, 2 Sep 2016 11:06:24 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Neil Leeder <nleeder@...eaurora.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Mark Langsdorf <mlangsdo@...hat.com>,
        Mark Salter <msalter@...hat.com>, Jon Masters <jcm@...hat.com>,
        Timur Tabi <timur@...eaurora.org>, cov@...eaurora.org
Subject: Re: [PATCH v4 2/2] soc: qcom: add l2 cache perf events driver

On Thu, Sep 01, 2016 at 05:30:52PM +0100, Mark Rutland wrote:
> On Tue, Aug 30, 2016 at 01:01:33PM -0400, Neil Leeder wrote:
> > +static DEFINE_MUTEX(l2cache_pmu_mutex);
> 
> A mutex (which can sleep) is not safe for the hotplug state machine
> stuff. See recent patches to the arm_pmu code.
> 
> That's further subsumed by the multi-instance stuff, so this (and the
> list) will not be necessary shortly.

This has *just* landed in tip. See the smp/hotplug branch [1]. The
arm_pmu change [2] should serve as an example of what to do.

Thanks,
Mark.

[1] https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/log/?h=smp/hotplug
[2] https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=smp/hotplug&id=cc727977acb0fe05b7aa1f00cccb893530820895