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,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 6D089C432BE for ; Fri, 30 Jul 2021 14:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 536B560720 for ; Fri, 30 Jul 2021 14:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239278AbhG3OUg (ORCPT ); Fri, 30 Jul 2021 10:20:36 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:55350 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239111AbhG3ORM (ORCPT ); Fri, 30 Jul 2021 10:17:12 -0400 Message-ID: <20210730135205.434944891@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1627654627; 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=yFddNLcBiutB/8vMLREBAPQ8WzNzATHga0WkaGc9nqk=; b=Rmooj/i5QN/LtyCq0Q/sj8b7JbEEnrfBXXJ+G1bCAlf8O2dPB90Yv2hLt6Sjbufj2JvYDE nT/RmwMSduadWwTLwrWXOqKsOf9/uR+q2Q5/79KaBUB5hijfhZ3efwhL2i0IjDeCgLX/a7 c7UpDVPwGBd2/frZrvn9whK51B0+g0cnM64FvdV/63c6ABESf357G4TvTdWeHrw/lUjXQv RlikQffgUVxe1fIPoiGlDEpr4oy3GOy7CRle16lAeAUgqgyrXlgtgqdHtbn+iGsqtL3A/V qADcFhGcgysB4fDc4vbGEq3XMdrvNv0gGQPO4hxVQw/nCjLtYrZtIAHnGaP0Yw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1627654627; 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=yFddNLcBiutB/8vMLREBAPQ8WzNzATHga0WkaGc9nqk=; b=rGptN9ky84KqLNLX9ICYmkfnBm6WZFm7YFYcI0QT66K3zi2BT5upjJzNDhliElAj95p+BY keXszrqGGhmXzPDw== Date: Fri, 30 Jul 2021 15:50:12 +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 05/63] sched: Provide schedule point for RT locks References: <20210730135007.155909613@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 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 seperate scheduling point for this and hand a new scheduling mode argument to __schedule() which allows along with seperate 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 @@ -294,6 +294,9 @@ 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 @@ -5831,7 +5831,13 @@ 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. @@ -6136,6 +6142,18 @@ 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 {