From patchwork Mon Jun 12 09:07:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 13276026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D38BFC87FDC for ; Mon, 12 Jun 2023 09:55:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235511AbjFLJzx (ORCPT ); Mon, 12 Jun 2023 05:55:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231855AbjFLJyZ (ORCPT ); Mon, 12 Jun 2023 05:54:25 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A25155FF3; Mon, 12 Jun 2023 02:38:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=9sqy4wj1SuZG+E1ZOkNDiw8zR5F8T4bHRpYkByM8S6o=; b=HNjtc1kou6jUKrPa93YlSTKipB VhOpXUPSBCgjriMwtuZYiFbSO92NjXbfCsFmRFtzO7yfFSXIVuY/yN+Yj7pGBcnBI5S0hv8fNdtcN //wmbKzY575t4i5oKfCiWpecYl0rAG6BFfdMSjKIXuCRhpuWcyhO2gVcrMTipwAY6sjO79StTEAIQ VC8/ybwDlXuWf1vL/cHd1fVTSgl2eqKrBrD54rFBuftQGd/gu653fosXknQhYF8Op6cNrlThojVpp 8VS39gvDd4GbsgBVynRhv46UkSxPgULiSAQIabpdcmA7w8/j+yhjfaJwXT+KXZjarghiosRq198gW o3zyz1kQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1q8e0g-008kPB-1k; Mon, 12 Jun 2023 09:38:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0BFFE3031BE; Mon, 12 Jun 2023 11:38:49 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 5832930A77B57; Mon, 12 Jun 2023 11:38:48 +0200 (CEST) Message-ID: <20230612093538.712217968@infradead.org> User-Agent: quilt/0.66 Date: Mon, 12 Jun 2023 11:07:30 +0200 From: Peter Zijlstra To: torvalds@linux-foundation.org, keescook@chromium.org, gregkh@linuxfoundation.org, pbonzini@redhat.com Cc: masahiroy@kernel.org, nathan@kernel.org, ndesaulniers@google.com, nicolas@fjasle.eu, catalin.marinas@arm.com, will@kernel.org, vkoul@kernel.org, trix@redhat.com, ojeda@kernel.org, peterz@infradead.org, mingo@redhat.com, longman@redhat.com, boqun.feng@gmail.com, dennis@kernel.org, tj@kernel.org, cl@linux.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, irogers@google.com, adrian.hunter@intel.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, rientjes@google.com, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, apw@canonical.com, joe@perches.com, dwaipayanray1@gmail.com, lukas.bulwahn@gmail.com, john.johansen@canonical.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, llvm@lists.linux.dev, linux-perf-users@vger.kernel.org, rcu@vger.kernel.org, linux-security-module@vger.kernel.org, tglx@linutronix.de, ravi.bangoria@amd.com, error27@gmail.com, luc.vanoostenryck@gmail.com Subject: [PATCH v3 17/57] sched: Simplify yield_to() References: <20230612090713.652690195@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org Use guards to reduce gotos and simplify control flow. Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/core.c | 73 ++++++++++++++++++++++------------------------------ 1 file changed, 32 insertions(+), 41 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8799,55 +8799,46 @@ int __sched yield_to(struct task_struct { struct task_struct *curr = current; struct rq *rq, *p_rq; - unsigned long flags; int yielded = 0; - local_irq_save(flags); - rq = this_rq(); + scoped_guard (irqsave) { + rq = this_rq(); again: - p_rq = task_rq(p); - /* - * If we're the only runnable task on the rq and target rq also - * has only one task, there's absolutely no point in yielding. - */ - if (rq->nr_running == 1 && p_rq->nr_running == 1) { - yielded = -ESRCH; - goto out_irq; - } - - double_rq_lock(rq, p_rq); - if (task_rq(p) != p_rq) { - double_rq_unlock(rq, p_rq); - goto again; - } - - if (!curr->sched_class->yield_to_task) - goto out_unlock; - - if (curr->sched_class != p->sched_class) - goto out_unlock; - - if (task_on_cpu(p_rq, p) || !task_is_running(p)) - goto out_unlock; - - yielded = curr->sched_class->yield_to_task(rq, p); - if (yielded) { - schedstat_inc(rq->yld_count); + p_rq = task_rq(p); /* - * Make p's CPU reschedule; pick_next_entity takes care of - * fairness. + * If we're the only runnable task on the rq and target rq also + * has only one task, there's absolutely no point in yielding. */ - if (preempt && rq != p_rq) - resched_curr(p_rq); - } + if (rq->nr_running == 1 && p_rq->nr_running == 1) + return -ESRCH; -out_unlock: - double_rq_unlock(rq, p_rq); -out_irq: - local_irq_restore(flags); + guard(double_rq_lock)(rq, p_rq); + if (task_rq(p) != p_rq) + goto again; + + if (!curr->sched_class->yield_to_task) + return 0; + + if (curr->sched_class != p->sched_class) + return 0; + + if (task_on_cpu(p_rq, p) || !task_is_running(p)) + return 0; + + yielded = curr->sched_class->yield_to_task(rq, p); + if (yielded) { + schedstat_inc(rq->yld_count); + /* + * Make p's CPU reschedule; pick_next_entity + * takes care of fairness. + */ + if (preempt && rq != p_rq) + resched_curr(p_rq); + } + } - if (yielded > 0) + if (yielded) schedule(); return yielded;