linux-kernel - Re: [PATCH v6 3/4] bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter

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Message-ID: <20150805101506.GY18673@twins.programming.kicks-ass.net>
Date:	Wed, 5 Aug 2015 12:15:06 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Kaixu Xia <xiakaixu@...wei.com>
Cc:	ast@...mgrid.com, davem@...emloft.net, acme@...nel.org,
	mingo@...hat.com, masami.hiramatsu.pt@...achi.com,
	jolsa@...nel.org, daniel@...earbox.net, wangnan0@...wei.com,
	linux-kernel@...r.kernel.org, pi3orama@....com, hekuang@...wei.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH v6 3/4] bpf: Implement function bpf_perf_event_read()
 that get the selected hardware PMU conuter

On Wed, Aug 05, 2015 at 12:04:25PM +0200, Peter Zijlstra wrote:
> On Tue, Aug 04, 2015 at 08:58:15AM +0000, Kaixu Xia wrote:

> > +	    event->ctx->task != current)

Strictly speaking we should hold rcu_read_lock around dereferencing
event->ctx (or have IRQs disabled -- although I know Paul doesn't like
us relying on that).


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