Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261194AbVAaNX4 (ORCPT ); Mon, 31 Jan 2005 08:23:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261195AbVAaNXz (ORCPT ); Mon, 31 Jan 2005 08:23:55 -0500 Received: from 213-239-205-147.clients.your-server.de ([213.239.205.147]:54940 "EHLO debian.tglx.de") by vger.kernel.org with ESMTP id S261194AbVAaNXw (ORCPT ); Mon, 31 Jan 2005 08:23:52 -0500 Subject: Re: [PATCH] rc2-mm2: unneeded cli/sti in fix-preemption-race patch From: Thomas Gleixner Reply-To: tglx@linutronix.de To: Oleg Nesterov Cc: LKML , Ingo Molnar , Andrew Morton In-Reply-To: <41FE319E.E265C599@tv-sign.ru> References: <41FE319E.E265C599@tv-sign.ru> Content-Type: text/plain Date: Mon, 31 Jan 2005 14:22:25 +0100 Message-Id: <1107177745.21196.333.camel@tglx.tec.linutronix.de> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 (2.0.3-2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2041 Lines: 70 On Mon, 2005-01-31 at 16:24 +0300, Oleg Nesterov wrote: > Hello. > > Thomas Gleixner wrote: > > > > The patch prevents this by leaving interrupts disabled and calling > > a seperate function preempt_schedule_irq(). > > sched-fix-preemption-race-core-i386.patch: > > > > +++ 25-akpm/arch/i386/kernel/entry.S > > @@ -189,6 +189,7 @@ ENTRY(resume_userspace) > > > > #ifdef CONFIG_PREEMPT > > ENTRY(resume_kernel) > > + cli > > I think this 'cli' is unneeded. resume_kernel: is used on > return path from do_IRQ() which leaves interrupts disabled. > irq_desc->handler->end() should not enable interrupts, yes? > > And we have preempt_stop==cli in ret_from_exception: case, > before ret_from_intr. Right. I missed the preempt_stop == cli. > > +++ 25-akpm/kernel/sched.c > > @@ -2872,6 +2872,48 @@ need_resched: > > ... > > +asmlinkage void __sched preempt_schedule_irq(void) > > +{ > > ... > > + local_irq_enable(); > > + schedule(); > > It is ok to enter schedule() with interrupts disabled, so this > 'sti' seems to be unneeded too. Makes sense. tglx > Signed-off-by: Oleg Nesterov > > --- 2.6.11-rc2-mm2/arch/i386/kernel/entry.S~ Mon Jan 31 14:09:37 2005 > +++ 2.6.11-rc2-mm2/arch/i386/kernel/entry.S Mon Jan 31 14:55:25 2005 > @@ -189,7 +189,6 @@ ENTRY(resume_userspace) > > #ifdef CONFIG_PREEMPT > ENTRY(resume_kernel) > - cli > cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ? > jnz restore_all > need_resched: > --- 2.6.11-rc2-mm2/kernel/sched.c~ Mon Jan 31 14:09:54 2005 > +++ 2.6.11-rc2-mm2/kernel/sched.c Mon Jan 31 14:57:44 2005 > @@ -2971,7 +2971,6 @@ need_resched: > saved_lock_depth = task->lock_depth; > task->lock_depth = -1; > #endif > - local_irq_enable(); > schedule(); > local_irq_disable(); > #ifdef CONFIG_PREEMPT_BKL - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/