From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752666AbbKOShR (ORCPT ); Sun, 15 Nov 2015 13:37:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44521 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752633AbbKOShN (ORCPT ); Sun, 15 Nov 2015 13:37:13 -0500 Date: Sun, 15 Nov 2015 20:33:14 +0100 From: Oleg Nesterov To: Ingo Molnar , Peter Zijlstra Cc: Milos Vyletel , Prarit Bhargava , Tejun Heo , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH 2/8] stop_machine: don't disable preemption in stop_two_cpus() Message-ID: <20151115193314.GA8249@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151115193254.GA8225@redhat.com> 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 Now that stop_two_cpus() path does not check cpu_active() we can remove preempt_disable(), it was only needed to ensure that stop_machine() can not be called after we observe cpu_active() == T and before we queue the new work. Also, turn the pointless and confusing ->executed check into WARN_ON(). We know that both works must be executed, otherwise we have a bug. And in fact I think that done->executed should die, see the next changes. Signed-off-by: Oleg Nesterov --- kernel/stop_machine.c | 11 +++-------- 1 files changed, 3 insertions(+), 8 deletions(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 1a66a95..17f01a9 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -258,7 +258,6 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * struct cpu_stop_work work1, work2; struct multi_stop_data msdata; - preempt_disable(); msdata = (struct multi_stop_data){ .fn = fn, .data = arg, @@ -277,16 +276,12 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * if (cpu1 > cpu2) swap(cpu1, cpu2); - if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) { - preempt_enable(); + if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) return -ENOENT; - } - - preempt_enable(); wait_for_completion(&done.completion); - - return done.executed ? done.ret : -ENOENT; + WARN_ON(!done.executed); + return done.ret; } /** -- 1.5.5.1