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 0B22DC4338F for ; Sun, 15 Aug 2021 21:28:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E48B261378 for ; Sun, 15 Aug 2021 21:28:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230512AbhHOV30 (ORCPT ); Sun, 15 Aug 2021 17:29:26 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:47824 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231362AbhHOV2T (ORCPT ); Sun, 15 Aug 2021 17:28:19 -0400 Message-ID: <20210815211302.372319055@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1629062868; 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=SZqMfIhfNpT8/bCIRlDGg8ulBul554WecW173Sc7lKg=; b=pQ2fAW94nK7sHM8csKVM6778XDqoFxlgWYi8IAr0fNv84M8RgJv1+SpS27eAm+g2jC1beo Iz/rzypBUMhkQ0nOwAaD3P3deX3Za+gwUbkn5LnAN98k7ZAlZRjpbF63I9vMaqxsK601u2 5sXSFfEMK3GYzOFYMWedAizSzcNppii5O5jvAogFh4kFHgjNuBnSkrYK+dcR+aFDjAZwv6 YkXNsqKttl9Q2VHS8YBB3YBknf34HyVQQwqwujGvih6sdZvAzz8AuMLaQFTLFR35MA4QYa 0sOe02BTG06adR75BxotZ2TMfD/2JPU1DVBUcY6fOtHyA+HEhkb5gigSCaZbNg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1629062868; 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=SZqMfIhfNpT8/bCIRlDGg8ulBul554WecW173Sc7lKg=; b=cLE8uymWNMTbIF5aqbH2XuV463OYofAqLnnaV+hsAxCXH5nCKT3r29GhEd4qagXknla/fF 5zD6Pmo4k/t5o4CQ== 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 , Mike Galbraith Subject: [patch V5 08/72] sched: Provide schedule point for RT locks References: <20210815203225.710392609@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Date: Sun, 15 Aug 2021 23:27:48 +0200 (CEST) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner RT enabled kernels substitute spin/rwlocks with 'sleeping' variants based on rtmutex. Blocking on such a lock is similar to preemption versus: - I/O scheduling and worker handling because these functions might block on another substituted lock or come from a lock contention within these functions. - RCU considers this like a preemption because the task might be in a read side critical section. Add a separate scheduling point for this and hand a new scheduling mode argument to __schedule() which allows along with separate mode masks to handle this gracefully from within the scheduler without proliferating that to other subsystems like RCU. Signed-off-by: Thomas Gleixner --- V2: Adopt to the simplified mask logic --- include/linux/sched.h | 3 +++ kernel/sched/core.c | 20 +++++++++++++++++++- 2 files changed, 22 insertions(+), 1 deletion(-) --- --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -288,6 +288,9 @@ extern long schedule_timeout_idle(long t asmlinkage void schedule(void); extern void schedule_preempt_disabled(void); asmlinkage void preempt_schedule_irq(void); +#ifdef CONFIG_PREEMPT_RT + extern void schedule_rtlock(void); +#endif extern int __must_check io_schedule_prepare(void); extern void io_schedule_finish(int token); --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5829,7 +5829,13 @@ pick_next_task(struct rq *rq, struct tas */ #define SM_NONE 0x0 #define SM_PREEMPT 0x1 -#define SM_MASK_PREEMPT (~0U) +#define SM_RTLOCK_WAIT 0x2 + +#ifndef CONFIG_PREEMPT_RT +# define SM_MASK_PREEMPT (~0U) +#else +# define SM_MASK_PREEMPT SM_PREEMPT +#endif /* * __schedule() is the main scheduler function. @@ -6134,6 +6140,18 @@ void __sched schedule_preempt_disabled(v preempt_disable(); } +#ifdef CONFIG_PREEMPT_RT +void __sched notrace schedule_rtlock(void) +{ + do { + preempt_disable(); + __schedule(SM_RTLOCK_WAIT); + sched_preempt_enable_no_resched(); + } while (need_resched()); +} +NOKPROBE_SYMBOL(schedule_rtlock); +#endif + static void __sched notrace preempt_schedule_common(void) { do {