Date: Fri, 3 Feb 2012 08:25:19 -0800
From: Tejun Heo <tj@kernel.org>
To: Andrew Vagin <avagin@openvz.org>
Cc: linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
        Roland McGrath <roland@redhat.com>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Pavel Emelyanov <xemul@parallels.com>
Subject: Re: [PATCH] ptrace: add ability to get clear_tid_address
Message-ID: <20120203162519.GB805@google.com>
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On Fri, Feb 03, 2012 at 02:11:23PM +0300, Andrew Vagin wrote:
> Zero is written at clear_tid_address, when the process exits.
> This functionality is used by pthread_join().
> 
> sys_set_tid_address() changes this address for current task.
> 
> Before this patch clear_tid_address could not be got from user space.
> I want to dump a full state of a task, so I need this address.
> Also I think it may be useful for debugging a multithreading program.
> 
> I am not sure that ptrace is suitable place. It may be added in prctl,
> but I think it's a bit useless and strange. I can't image a real
> situation (avoid checkpointing) when a thread will want to get own
> clear_tid_address from itself, this address is used by parent ussually.
> 
> Signed-off-by: Andrew Vagin <avagin@openvz.org>

Ummm... this really doesn't fit in ptrace.  Cyrill, why not put it
together with other params you're exporting?

Thanks.

-- 
tejun
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