linux-kernel - Re: [PATCH] copy_process: remove the unneeded clear_tsk_thread_flag(TIF

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Message-Id: <20090428023919.E2311FC3C6@magilla.sf.frob.com>
Date:	Mon, 27 Apr 2009 19:39:19 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] copy_process: remove the unneeded
	clear_tsk_thread_flag(TIF_SIGPENDING)

Acked-by: Roland McGrath <roland@...hat.com>

> The forked child can have TIF_SIGPENDING if it was copied from parent's
> ti->flags. But this is harmless and actually almost never happens, because
> copy_process() can't succeed if signal_pending() == T.

When it does happen, it's actually improper to clear it.  In a CLONE_THREAD
case, the pending signals might include shared_pending signals that the
child too should take.  (Arguably there is no way to notice, since the
parent thread will be racing to dequeue the same signals.)


Thanks,
Roland
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