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Date: Sat, 17 Oct 2015 12:00:54 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, ak@linux.intel.com,
        edumazet@google.com, acme@redhat.com
Subject: Re: [PATCH] perf/core: fix RCU issues with cgroup monitoring mode
Message-ID: <20151017100054.GF3816@twins.programming.kicks-ass.net>
References: <20151017012811.GA18581@thinkpad>
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On Sat, Oct 17, 2015 at 03:28:11AM +0200, Stephane Eranian wrote:
>  static int __perf_cgroup_move(void *info)
>  {
>  	struct task_struct *task = info;
> +	rcu_read_lock();
>  	perf_cgroup_switch(task, PERF_CGROUP_SWOUT | PERF_CGROUP_SWIN);
> +	rcu_read_unlock();
>  	return 0;
>  }

On second thought, how can this be right? Surely the cgroup system has
cgroups stabilized over calling ->attach() ?