From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752732Ab1HPRxH (ORCPT ); Tue, 16 Aug 2011 13:53:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31936 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752409Ab1HPRxE (ORCPT ); Tue, 16 Aug 2011 13:53:04 -0400 Date: Tue, 16 Aug 2011 18:49:28 +0200 From: Oleg Nesterov To: Matt Fleming Cc: linux-kernel@vger.kernel.org, Jonas Bonn , Arnd Bergmann Subject: Re: [PATCH 18/41] OpenRISC: Don't reimplement force_sigsegv() Message-ID: <20110816164928.GA29190@redhat.com> References: <1313071035-12047-1-git-send-email-matt@console-pimps.org> <1313071035-12047-19-git-send-email-matt@console-pimps.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1313071035-12047-19-git-send-email-matt@console-pimps.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/11, Matt Fleming wrote: > > Instead of open coding the sequence from force_sigsegv() just call > it. This also fixes a race because sa_handler was being modified > without holding ->sighand->siglock. > > --- a/arch/openrisc/kernel/signal.c > +++ b/arch/openrisc/kernel/signal.c > @@ -257,9 +257,7 @@ static void setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info, > return; > > give_sigsegv: > - if (sig == SIGSEGV) > - ka->sa.sa_handler = SIG_DFL; > - force_sig(SIGSEGV, current); > + force_sigsegv(sig, current); > } Agreed, but... I don't really understand the changelog, which race this patch fix? Yes, we shouldn't change sa_handler lockless, this "breaks the rules" but I do not see any immediate problem. And since force_sigsegv() drops the lock after setting SIG_DFL we can "race" with the sub-thread anyway. Hmm. Looking more, I think that this patch is not the cleanup, but the bugfix. The current code is simply wrong, it plays with ka, and it points to the _copy_ of sighand->action[], so this code is simply pointless. Unless I missed something, could you fix the changelog and resend? Oleg.