linux-kernel - Re: [PATCH 1/1] exec: do not sleep in TASK_TRACED under ->cred_guard

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Message-Id: <20090903200924.E46DF47C94@magilla.sf.frob.com>
Date:	Thu,  3 Sep 2009 13:09:24 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	James Morris <jmorris@...ei.org>,
	Tom Horsley <tom.horsley@....net>,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH 1/1] exec: do not sleep in TASK_TRACED under
	->cred_guard_mutex

I certainly think it's right to hold the mutex only as long as necessary.
Clearly holding it when we stop is wrong.

I'm a bit concerned about holding it for arbitrary periods while we block
in the filesystem code.  e.g., consider the scenario with a hangs-forever
NFS server or suchlike.  But I'm not sure there is a reasonable way around
that one.

The paired calls that leave the mutex locked in between should have some
clear comments calling attention to their pairing.  Aside from that making
sure that subtlety is clear, I don't see any problems in the patch off hand.
But I haven't scoured the code path lately to have full confidence.
I'd like to hear David's reactions.

Thanks,
Roland
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