linux-kernel - Re: PATCH? tracehook_report

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Message-Id: <20090601231939.223CEFC3C7@magilla.sf.frob.com>
Date:	Mon,  1 Jun 2009 16:19:39 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: PATCH? tracehook_report_clone: fix false positives

> I suspect you misread my previous question.

Apparently so.

> I didn't mean PTRACE_ATTACH should use ptrace_init_task). I just meant that
> perhaps it makes sense to move sigaddset() from tracehook_finish_clone()
> to tracehook_finish_clone()->ptrace_init_task().

You mean from tracehook_report_clone to ptrace_init_task.  Perhaps.
tracehook_finish_clone->ptrace_init_task is inside write_lock_irq,
so it should really be kept to the minimum of what has to be inside there.

But the real reason is just that tracehook_report_clone() is called at the
place in do_fork() where the ptrace SIGSTOP code was originally before the
introduction of tracehook.h.  

This is where the utrace attachment point has to be (i.e. outside all the
locking).  So I don't see any benefit to changing the ptrace status quo now
for its own sake.

Thanks,
Roland
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