linux-kernel - Re: [PATCH v2] Make PTRACE_SEIZE set ptrace options specified in 'data' parameter

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Date:	Tue, 13 Sep 2011 17:00:04 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>,
	linux-kernel@...r.kernel.org, dvlasenk@...hat.com
Subject: Re: [PATCH v2] Make PTRACE_SEIZE set ptrace options specified in
 'data' parameter

On Sun, Sep 11, 2011 at 08:14:42PM +0200, Oleg Nesterov wrote:
> We need to rework the locking, yes. But we need the lock which protects
> the parent's list_head (currently we rely on tasklist). Yes, a single
> lock can't help. We already use ->cred_guard_mutex though.
> 
> This needs more thinking, but imho child->siglock is pointless here.

But we can at least guarantee that if ->ptrace is set (or clear) while
tracee's siglock is held, its ->parent points to the tracer (or not).
At any rate, AFAICS, this currently doesn't really matter.  I
suggested it mainly because it would make the locking change easier.

Thanks.

-- 
tejun
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