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Date: Wed, 27 Jan 2016 09:44:43 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Sasha Levin <sasha.levin@oracle.com>, linux-kernel@vger.kernel.org,
        mingo@kernel.org
Subject: Re: [PATCH] signals: work around random wakeups in sigsuspend()
Message-ID: <20160127084443.GL6357@twins.programming.kicks-ass.net>
References: <1453735306-13519-1-git-send-email-sasha.levin@oracle.com>
 <20160125133205.36542c86ada93761d8a9ff06@linux-foundation.org>
 <20160126211009.GA4695@redhat.com>
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On Tue, Jan 26, 2016 at 10:10:09PM +0100, Oleg Nesterov wrote:

> And, ironically, there is another more serious "reverse" problem ;) sigsuspend()
> orany other user of -ERESTARTNOHAND can "miss" the signal, in a sense that the
> kernel can wrongly restart this syscall after return from signal handler. This
> is not trivial to fix..

So I'm not entirely sure I get what you mean there. But it did get me to
look at the patch again:

+       while (!signal_pending(current)) {
+               __set_current_state(TASK_INTERRUPTIBLE);
+               schedule();
+       }

That should very much be:

	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (signal_pending(current))
			break;
		schedule();
	}
	__set_current_state(TASK_RUNNING);