linux-kernel - Re: [PATCH 7/7] pid: get pid_t ppid of task in init_pid

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Message-ID: <20140220190114.GC23993@redhat.com>
Date:	Thu, 20 Feb 2014 20:01:22 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	eparis@...hat.com, sgrubb@...hat.com, akpm@...ux-foundation.org,
	peterz@...radead.org, stable@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 7/7] pid: get pid_t ppid of task in init_pid_ns

On 01/23, Richard Guy Briggs wrote:
>
> Added the functions task_ppid_nr_ns() and task_ppid_nr() to abstract the lookup
> of the PPID (real_parent's pid_t) of a process, including rcu locking, in the
> arbitrary and init_pid_ns.
> This provides an alternative to sys_getppid(), which is relative to the child
> process' pid namespace.

I agree, this makes sense.


imho it would be better to send this patch along with sys_getppid()
conversions, but I won't argue.

> +static int pid_alive(const struct task_struct *p);
> +static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)
> +{
> +	pid_t pid = 0;
> +
> +	rcu_read_lock();
> +	if (pid_alive(tsk))
> +		pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns);
> +	rcu_read_unlock();
> +
> +	return pid;
> +}

Perhaps it should be named task_ptgid_nr_ns() or even parent_tgid_nr_ns().
Since it returns tgid, not pid (== tid).

But this is cosmetic, I won't insist.

Oleg.

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