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Date: Thu, 7 Jul 2011 21:03:01 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>
Cc: vda.linux@googlemail.com, jan.kratochvil@redhat.com,
        pedro@codesourcery.com, indan@nul.nu, bdonlan@gmail.com,
        linux-kernel@vger.kernel.org
Subject: [PATCH 0/1] ptrace: fix ptrace_signal() && STOP_DEQUEUED
	interaction
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Another very annoying and ancient problem which needs the fix,
and any fix obviously adds the subtle user-visible changes.

In short, in general it is simply impossible to know whether
PTRACE_CONT(SIGSTOP) will stop the tracee or not.

ee77f075 "signal: Turn SIGNAL_STOP_DEQUEUED into GROUP_STOP_DEQUEUED"
makes the things better, at least STOP_DEQUEUED can't be set/cleared
by another thread, but still without this patch the behavior is not
clearly defined.

Oleg.