From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 933B1C34022 for ; Mon, 17 Feb 2020 15:40:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72B8E24654 for ; Mon, 17 Feb 2020 15:40:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729288AbgBQPky (ORCPT ); Mon, 17 Feb 2020 10:40:54 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:60067 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729163AbgBQPkx (ORCPT ); Mon, 17 Feb 2020 10:40:53 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j3iVt-0000DK-Al; Mon, 17 Feb 2020 16:40:49 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id ED0B31C20B0; Mon, 17 Feb 2020 16:40:48 +0100 (CET) Date: Mon, 17 Feb 2020 15:40:48 -0000 From: "tip-bot2 for Alexander Popov" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: timers/core] timer: Improve the comment describing schedule_timeout() Cc: Alexander Popov , Thomas Gleixner , x86 , LKML In-Reply-To: <20200117225900.16340-1-alex.popov@linux.com> References: <20200117225900.16340-1-alex.popov@linux.com> MIME-Version: 1.0 Message-ID: <158195404873.13786.15386976838867455888.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the timers/core branch of tip: Commit-ID: 1b8020618b8922b9128b3015224221d0f869b471 Gitweb: https://git.kernel.org/tip/1b8020618b8922b9128b3015224221d0f869b471 Author: Alexander Popov AuthorDate: Sat, 18 Jan 2020 01:59:00 +03:00 Committer: Thomas Gleixner CommitterDate: Mon, 17 Feb 2020 16:36:05 +01:00 timer: Improve the comment describing schedule_timeout() When working commit 6dcd5d7a7a29c1e, a mistake was noticed by Linus: schedule_timeout() was called without setting the task state to anything particular. It calls the scheduler, but doesn't delay anything, because the task stays runnable. That happens because sched_submit_work() does nothing for tasks in TASK_RUNNING state. That turned out to be the intended behavior. Adding a WARN() is not useful as the task could be woken up right after setting the state and before reaching schedule_timeout(). Improve the comment about schedule_timeout() and describe that more explicitly. Signed-off-by: Alexander Popov Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200117225900.16340-1-alex.popov@linux.com --- kernel/time/timer.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4820823..cb34fac 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1828,21 +1828,23 @@ static void process_timeout(struct timer_list *t) * schedule_timeout - sleep until timeout * @timeout: timeout value in jiffies * - * Make the current task sleep until @timeout jiffies have - * elapsed. The routine will return immediately unless - * the current task state has been set (see set_current_state()). + * Make the current task sleep until @timeout jiffies have elapsed. + * The function behavior depends on the current task state + * (see also set_current_state() description): * - * You can set the task state as follows - + * %TASK_RUNNING - the scheduler is called, but the task does not sleep + * at all. That happens because sched_submit_work() does nothing for + * tasks in %TASK_RUNNING state. * * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to * pass before the routine returns unless the current task is explicitly - * woken up, (e.g. by wake_up_process())". + * woken up, (e.g. by wake_up_process()). * * %TASK_INTERRUPTIBLE - the routine may return early if a signal is * delivered to the current task or the current task is explicitly woken * up. * - * The current task state is guaranteed to be TASK_RUNNING when this + * The current task state is guaranteed to be %TASK_RUNNING when this * routine returns. * * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule @@ -1850,7 +1852,7 @@ static void process_timeout(struct timer_list *t) * value will be %MAX_SCHEDULE_TIMEOUT. * * Returns 0 when the timer has expired otherwise the remaining time in - * jiffies will be returned. In all cases the return value is guaranteed + * jiffies will be returned. In all cases the return value is guaranteed * to be non-negative. */ signed long __sched schedule_timeout(signed long timeout)