Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756129Ab3G2RTa (ORCPT ); Mon, 29 Jul 2013 13:19:30 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:43394 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752813Ab3G2RT2 (ORCPT ); Mon, 29 Jul 2013 13:19:28 -0400 From: Abbas Raza To: linux-kernel@vger.kernel.org Cc: Abbas Raza , Peter Zijlstra , Ingo Molnar Subject: [PATCH] sched: don't wait in kthread_bind for presmp initcalls Date: Mon, 29 Jul 2013 22:19:08 +0500 Message-Id: <1375118348-25253-1-git-send-email-abbas_raza@mentor.com> X-Mailer: git-send-email 1.8.3.2 X-OriginalArrivalTime: 29 Jul 2013 17:19:23.0336 (UTC) FILETIME=[C4F3A480:01CE8C7F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1852 Lines: 60 From: Abbas Raza wait_task_inactive shouldn't be called in kthread_bind for presmp initcalls the same way it is done in !SMP case. more info here: http://permalink.gmane.org/gmane.linux.kernel.embedded/4046 This patch improves boot time for pre-smp initcalls as given below initcall spawn_ksoftirqd+0x0/0x54 returned 0 after 0 usecs initcall init_workqueues+0x0/0x358 returned 0 after 0 usecs initcall cpu_stop_init+0x0/0xcc returned 0 after 0 usecs boot time without this patch: initcall spawn_ksoftirqd+0x0/0x54 returned 0 after 9765 usecs initcall init_workqueues+0x0/0x358 returned 0 after 9765 usecs initcall cpu_stop_init+0x0/0xcc returned 0 after 19531 usecs Signed-off-by: Abbas Raza Cc: Peter Zijlstra Cc: Ingo Molnar --- kernel/kthread.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index b579af5..80f19b5 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -221,10 +221,15 @@ EXPORT_SYMBOL(kthread_create_on_node); */ void kthread_bind(struct task_struct *p, unsigned int cpu) { - /* Must have done schedule() in kthread() before we set_task_cpu */ - if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { - WARN_ON(1); - return; + if (!((num_online_cpus() == 1) && !cpu)) { + /* + * Must have done schedule() in kthread() before + * we set_task_cpu + */ + if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { + WARN_ON(1); + return; + } } /* It's safe because the task is inactive. */ -- 1.8.3.2 -- 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/