linux-kernel - Re: waitpid(WNOHANG) should report SIGCHLD-notified signals [Re: [PATCH 09/11] job control: reorganize wait_task

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Date:	Mon, 16 May 2011 14:11:16 +0200
From:	Jan Kratochvil <jan.kratochvil@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Oleg Nesterov <oleg@...hat.com>, vda.linux@...glemail.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu
Subject: Re: waitpid(WNOHANG) should report SIGCHLD-notified signals  [Re:
 [PATCH 09/11] job control: reorganize wait_task_stopped()]

Hi Tejun,

On Mon, 16 May 2011 11:13:18 +0200, Tejun Heo wrote:
> On Sun, May 15, 2011 at 07:47:22PM +0200, Jan Kratochvil wrote:
> > If the debugger wants to be single-threaded ("poll() model", not "threads
> > model") and it wants to communicate with user and examine debuggee symbols and
> > memory data it cannot use sleeping wait.  GDB is single-threaded and it
> > supports `set target-async 1': info '(gdb)Background Execution'
> 
> I don't think target-async is necessarily related.  It doesn't really
> matter whether the execution per-se is async or not.  The ptracer can
> be a separate thread

It cannot as various GDB-supported platforms do not support threads properly.
And you want to have a common codebase to get it will supported.

Besides that it is a matter of coding style, I perfer "poll() model" even on
threads-supporting GNU/Linux.


> Anyways, I would recommend using sleeping wait(2)'s for ptrace event
> tracking.

You cannot as I described above.


Thanks,
Jan
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