linux-kernel - Re: [PATCHSET RFC] ptrace,signal: clean transition between STOPPED and TRACED

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Date:	Tue,  1 Feb 2011 21:39:31 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	oleg@...hat.com, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCHSET RFC] ptrace,signal: clean transition between STOPPED
 and TRACED

> Also, the first test of xcheck seems to enter infinite loop.

It's a test for race-condition bugs, where the original test was to run the
infinite loop until it crashed.  As now written, it runs the loop until
$TESTTIME seconds have passed, defaulting to 10.  With various buggy
kernels in various configurations and on various machines, the time it
takes to get to a crash has varied widely.

> I see.  Yeah, if there are users which expect /proc/pid/status to be
> certain value, we can either emulate it or delay TRACED transition to
> the next PTRACE call *after* ATTACH/wait(2) sequence, but I think both
> are quite ugly and would like to avoid if at all possible.

I agree.  We just need to be more clearly sure about userland requirements
before we make changes.  I hope the answer is that nothing other than these
synthetic test cases actually relies on which one /proc/pid/status reports.
(That is, if they do check it, they only notice the "T".)

Thanks,
Roland
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