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From: Roland McGrath <roland@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
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Cc: Jan Kratochvil <jan.kratochvil@redhat.com>,
        Project Archer <archer@sourceware.org>
Subject: Re: ptrace improvement: PTRACE_O_INHERIT
In-Reply-To: Oleg Nesterov's message of  Saturday, 19 February 2011 21:29:21 +0100 <20110219202921.GA12280@redhat.com>
References: <20110214193052.3EC8D1814BA@magilla.sf.frob.com>
	<20110214193812.GA20765@redhat.com>
	<20110215003551.BC1EA1802A2@magilla.sf.frob.com>
	<20110215130805.GA30742@redhat.com>
	<20110215214333.GA18086@host1.dyn.jankratochvil.net>
	<20110215215634.2665A1806E0@magilla.sf.frob.com>
	<20110216193356.GB15576@redhat.com>
	<20110216194534.2D39018020E@magilla.sf.frob.com>
	<20110216200110.GA17601@redhat.com>
	<20110219194758.GA8994@host1.dyn.jankratochvil.net>
	<20110219202921.GA12280@redhat.com>
Message-Id: <20110221195405.D27B11801F8@magilla.sf.frob.com>
Date: Mon, 21 Feb 2011 19:54:00 -0000
X-SW-Source: 2011-q1/txt/msg00089.txt.bz2

> However. With or without PTRACE_O_TRACEEXIT, the thread can't go away
> until ptracer does do_wait(WEXITED). And until it does do_wait() tkill()
> succeeds even if the tracee is dead/zombie.

That is true except in the case of MT exec (de_thread).  The other threads
live in the process at the time when another does exec will be immediately
reaped without the chance for the debugger to see its death report.  I
think it's even a race to happen to see the death reports for these.  I'm
not managing to see how the immediate reaping happens in the source just
now, though I remember clearly that this is what happens.


Thanks,
Roland