linux-kernel - Re: [PATCH] ptrace: add ability to get clear_tid

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Date:	Wed, 8 Feb 2012 00:56:39 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Pedro Alves <palves@...hat.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	Tejun Heo <tj@...nel.org>, Andrew Vagin <avagin@...nvz.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ptrace: add ability to get clear_tid_address

On Tue, Feb 07, 2012 at 08:07:38PM +0000, Pedro Alves wrote:
> On 02/03/2012 04:51 PM, Oleg Nesterov wrote:
> > On 02/03, Pavel Emelyanov wrote:
> 
> >> Because there's no need for current to get this value of himself, but can
> >> be useful for e.g. gdb.
> > 
> > OK, perhaps this makes sense, I do not know.
> > 
> > Jan, Pedro, do you think gdb can use PTRACE_GET_TID_ADDRESS (returns
> > tracee->clear_child_tid) ?
> 
> Off hand, I'm not picturing a use.  But that may well just mean I'm lacking
> imagination.  Andrew, Pavel, did you have a particular idea in mind when you
> said it may be useful for debugging a multithreading program / gdb?
> 

Might not we set up hw watchpoint on this address and get interrupt
before pthread-join will find it? (To be fair I'm not sure if such
trick will work, didn't test ;)

	Cyrill
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