linux-kernel - Re: [GIT PULL rcu/next] RCU commits for 3.1

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Date:	Tue, 8 Nov 2011 14:10:16 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Li Zefan <lizf@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	eric.dumazet@...il.com, shaohua.li@...el.com, ak@...ux.intel.com,
	mhocko@...e.cz, alex.shi@...el.com, efault@....de,
	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>
Subject: Re: [GIT PULL rcu/next] RCU commits for 3.1

hardcoding 1 (true) assumes we will always call perf_cgroup_set_timestamp()
on current task. That's true today but we should make sure we don't
miss an error
if we ever change that in the future.


On Mon, Nov 7, 2011 at 6:55 PM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Mon, Nov 07, 2011 at 06:09:49PM +0100, Peter Zijlstra wrote:
>> On Mon, 2011-11-07 at 08:56 -0800, Paul E. McKenney wrote:
>> >
>> > If this really is a false positive, what should be used to get rid of
>> > the splats?
>>
>>
>> Probably something slightly less horrid than the below.. ;-)
>
> Hmmm...  Could the "1" below be replaced by the task's reference count?
> Probabilistic, but should eventually catch it.
>
>                                                        Thanx, Paul
>
>> ---
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index d1a1bee..8f05201 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -229,7 +229,7 @@ static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
>>  static inline struct perf_cgroup *
>>  perf_cgroup_from_task(struct task_struct *task)
>>  {
>> -     return container_of(task_subsys_state(task, perf_subsys_id),
>> +     return container_of(task_subsys_state_check(task, perf_subsys_id, 1),
>>                       struct perf_cgroup, css);
>>  }
>>
>>
>
>
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