linux-kernel - Re: [PATCH] [RFC] fix missed SIGCONT cases

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Message-ID: <Pine.LNX.4.64.0802281633540.3391@jikos.suse.cz>
Date:	Thu, 28 Feb 2008 16:40:49 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Roland McGrath <roland@...hat.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC] fix missed SIGCONT cases

On Thu, 28 Feb 2008, Oleg Nesterov wrote:

> BTW, I think we have the same problem when handle_stop_signal() does 
> do_notify_parent_cldstop(p, CLD_STOPPED) above. The multithreaded app in 
> the middle of the group stop can resume without actually seeing SIGCONT, 
> no?

Yes, I think so, this would also need fixing.

> Currently I have the very vagues idea, please see the "patch" below (it 
> is not right of course, just for illustration).
> These unlock(->siglock)'s on the signal sending path are really nasty,
> it would be wonderfull to avoid them. Note also sig_needs_tasklist(),
> we take tasklist_lock() exactly because we will probably drop siglock.

Whould it be problematic to change do_notify_parent_cldstop() so that it 
doesn't acquire siglock, but asumes that is is called with siglock held 
instead? I can't immediately see any reason why this shouldn't be 
possible.

> What do you think about the approach at least?

So it basically does the same thing my patch did -- postpones signalling 
the parent until it is safe, right?

Thanks,

-- 
Jiri Kosina
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