linux-kernel - Re: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was Vpid:)

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Message-ID: <20110615184625.GA15573@redhat.com>
Date:	Wed, 15 Jun 2011 20:46:25 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Greg Kurz <gkurz@...ibm.com>
Cc:	akpm@...ux-foundation.org, containers@...ts.osdl.org,
	linux-kernel@...r.kernel.org, serge@...lyn.com,
	daniel.lezcano@...e.fr, ebiederm@...ssion.com, xemul@...nvz.org
Subject: Re: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was
	Vpid:)

On 06/15, Greg Kurz wrote:
>
> @@ -176,6 +177,17 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
>  		if (tracer)
>  			tpid = task_pid_nr_ns(tracer, ns);
>  	}
> +	actpid = 0;
> +	sighand = rcu_dereference(p->sighand);
> +	if (sighand) {
> +		struct pid_namespace *pid_ns;
> +		unsigned long flags;
> +		spin_lock_irqsave(&sighand->siglock, flags);

Well. This is not exactly right. We have lock_task_sighand() for this.

But. Why do you need ->siglock? Why rcu_read_lock() is not enough?

Hmm. You don't even need pid_ns afaics, you could simply look at
pid->numbers[pid->level].

Oleg.

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