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Message-ID: <20120214182427.GA25119@redhat.com>
Date: Tue, 14 Feb 2012 19:24:27 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: David Howells <dhowells@...hat.com>
Cc: Matt Fleming <matt@...sole-pimps.org>, linux-arch@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Matt Fleming <matt.fleming@...el.com>,
Koichi Yasutake <yasutake.koichi@...panasonic.com>,
Al Viro <viro@...iv.linux.org.uk>, linux-am33-list@...hat.com
Subject: Re: [PATCH 20/40] mn10300: Use set_current_blocked() and
block_sigmask()
On 02/14, David Howells wrote:
>
> Oleg Nesterov <oleg@...hat.com> wrote:
>
> > No, only current can change ->blocked. This is even documented in
> > sigprocmask(). And more, the only correct way to change ->blocked
> > is set_current_blocked(). OK, with a couple of "I know what I am
> > doing" exceptions in kernel/signal.c.
>
> I was looking at force_sig_info() and derivatives. Is that what you refer to?
Ah, sorry, forgot to mention...
force_sig_info() (and its callers) need the cleanups and fixes. It
is almost always wrong if t != current.
For example, please look at
[PATCH 1/4] signal: give SEND_SIG_FORCED more power to beat SIGNAL_UNKILLABLE
http://marc.info/?l=linux-kernel&m=132890442717122
Hopefully we can fix all ab-users soon.
Just in case... if we race with force_sig_info() the task will be
killed anyway. But I agree, this is not nice and should be fixed.
And in any case, there are other places which assume it is safe
to read current->blocked lockless.
> If so, is it worth providing a force_sig_info_current(),
> force_sigsegv_current() and force_sig_current() to make things clearer to grep
> for, I wonder?
Yes, I think the "task_struct *t" argument should die.
Oleg.
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