linux-kernel - Re: [tip:perfcounters/core] perf_counter: Use PID namespaces properly

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Message-Id: <1243960085.13761.190.camel@twins>
Date:	Tue, 02 Jun 2009 18:28:05 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-tip-commits@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...hat.com, paulus@...ba.org, hpa@...or.com, mingo@...hat.com,
	jkacur@...hat.com, efault@....de, ebiederm@...ssion.com,
	mtosatti@...hat.com, tglx@...utronix.de,
	cjashfor@...ux.vnet.ibm.com, mingo@...e.hu
Subject: Re: [tip:perfcounters/core] perf_counter: Use PID namespaces
 properly

On Tue, 2009-06-02 at 17:55 +0200, Oleg Nesterov wrote:
> On 06/02, tip-bot for Peter Zijlstra wrote:
> >
> > +static u32 perf_counter_pid(struct perf_counter *counter, struct task_struct *p)
> > +{
> > +	/*
> > +	 * only top level counters have the pid namespace they were created in
> > +	 */
> > +	if (counter->parent)
> > +		counter = counter->parent;
> > +
> > +	return task_tgid_nr_ns(p, counter->ns);
> > +}
> > +
> > +static u32 perf_counter_tid(struct perf_counter *counter, struct task_struct *p)
> > +{
> > +	/*
> > +	 * only top level counters have the pid namespace they were created in
> > +	 */
> > +	if (counter->parent)
> > +		counter = counter->parent;
> > +
> > +	return task_pid_nr_ns(p, counter->ns);
> 
> Perhaps this should be
> 
> 	return task_pid_nr_ns(p->group_leader);
> 
> ?

That seems to be exactly what task_tgid_nr_ns() does.

so  pid = task->group_leader->pids[PIDTYPE_PID].pid
and tid = task->pids[PIDTYPE_PID].pid

> > +		tid_entry.pid = perf_counter_pid(counter, current);
> > +		tid_entry.tid = perf_counter_tid(counter, current);
> 
> 
> Otherwise we seem to always report .pid == .tid

tgid vs pid, I don't think they end up being equal. Are they?

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