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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6761CC07E95 for ; Tue, 13 Jul 2021 16:13:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 505C9610C7 for ; Tue, 13 Jul 2021 16:13:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230296AbhGMQQD (ORCPT ); Tue, 13 Jul 2021 12:16:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230122AbhGMQQB (ORCPT ); Tue, 13 Jul 2021 12:16:01 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EB78C0613DD for ; Tue, 13 Jul 2021 09:13:11 -0700 (PDT) Message-Id: <20210713160745.984154587@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1626192789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=PpGuo07G9t6v+7usOIACbdlfiq93zM9BMMU3eJZRQkc=; b=NqiL/Gldmq7kiTCpAch0PMsqT14FuPnyinI7uIaQqTMftjM0zsfGFzgZ7A7x0kTR4Y09ka PBCh1Ntk3Wi0UyOEgyD3lWq3jT4NF0ZYgQeTdeG3/zJZBsZzJRFYQbyo20EbAgcAzysoJh JeREPXb9FS+aqXbd42quxH1b5o0inUCSMZAlhBy4uDJ5BwuObEXw2d8gN5lU6ColPrrTa/ u9FXojl5QcMH4WuawotMCFiWfqT4LrvnNS6sSiB5mZDpOg2Qtqx6a0y3jn5mZwyuFn2XrH YBbHTBKWs812S+CXQ/iZ4tZ8vROoWIr8dAj9TI69Jbx2LSgC/3QGIBHJAMehEg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1626192789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=PpGuo07G9t6v+7usOIACbdlfiq93zM9BMMU3eJZRQkc=; b=X+Bf83xA4s9AAwp8dCiCPejTiTTSXneuuD1iVx1FRBSWZhQbDE7hvVHPdpgkh6byGfWutE x7VC/fctmO99BvCA== Date: Tue, 13 Jul 2021 17:10:55 +0200 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Steven Rostedt , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , Sebastian Andrzej Siewior , Davidlohr Bueso Subject: [patch 01/50] sched: Split out the wakeup state check References: <20210713151054.700719949@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner RT kernels have a slightly more complicated handling of wakeups due to 'sleeping' spin/rwlocks. If a task is blocked on such a lock then the original state of the task is preserved over the blocking and any regular (non lock related) wakeup has to be targeted at the saved state to ensure that these wakeups are not lost. Once the task acquired the lock it restores the task state from the saved state. To avoid cluttering try_to_wake_up() with that logic, split the wake up state check out into an inline helper and use it at both places where task::state is checked against the state argument of try_to_wake_up(). No functional change. Signed-off-by: Thomas Gleixner --- kernel/sched/core.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) --- --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3564,6 +3564,22 @@ static void ttwu_queue(struct task_struc } /* + * Invoked from try_to_wake_up() to check whether the task can be woken up. + * + * The caller holds p::pi_lock if p != current or has preemption + * disabled when p == current. + */ +static __always_inline +bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) +{ + if (READ_ONCE(p->__state) & state) { + *success = 1; + return true; + } + return false; +} + +/* * Notes on Program-Order guarantees on SMP systems. * * MIGRATION @@ -3702,10 +3718,9 @@ try_to_wake_up(struct task_struct *p, un * - we're serialized against set_special_state() by virtue of * it disabling IRQs (this allows not taking ->pi_lock). */ - if (!(READ_ONCE(p->__state) & state)) + if (!ttwu_state_match(p, state, &success)) goto out; - success = 1; trace_sched_waking(p); WRITE_ONCE(p->__state, TASK_RUNNING); trace_sched_wakeup(p); @@ -3720,14 +3735,11 @@ try_to_wake_up(struct task_struct *p, un */ raw_spin_lock_irqsave(&p->pi_lock, flags); smp_mb__after_spinlock(); - if (!(READ_ONCE(p->__state) & state)) + if (!ttwu_state_match(p, state, &success)) goto unlock; trace_sched_waking(p); - /* We're going to change ->state: */ - success = 1; - /* * Ensure we load p->on_rq _after_ p->state, otherwise it would * be possible to, falsely, observe p->on_rq == 0 and get stuck