From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A522881F for ; Mon, 12 Jun 2023 20:03:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=pxkiBpX/jKL5fDu+bPABhlXr0//9Lho2ZyF5gMf+wnU=; b=YE5cJbLdVZV9PIHrx4tBv08lZx QSYHEJWO1MpAuhw42QCCjHt/VjPVWsDm9s+u55fqbBeABzUnQBVsSlh2L+ituWNyN3T46KWVD9vks bbI8vIOnRcUIpyT/SDszF/Mi6utLS00YvmEtBFHbi+Lo2tFu+6BrCewpdECrJeO6RJwJiBZkWLNZl OvgWWjDTIsQqesRzGliidqy3dPAYen6WPMvkkSyTqGz+/O3tItjrXDxIUUXuSbtg7lF6hfVS+TZQR fdR4gQ2kcnekYTWSfwfK8uM/4Y+aX96zevoGSsdTz+GXLJ0gUd+CIgGmkrp59j/83fmqMK2G5dQBw 8Otb00PQ==; 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 1q8nkK-008zpU-0Q; Mon, 12 Jun 2023 20:02:36 +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) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 74E923002A9; Mon, 12 Jun 2023 22:02:30 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id ED3042460EAE4; Mon, 12 Jun 2023 22:02:29 +0200 (CEST) Date: Mon, 12 Jun 2023 22:02:29 +0200 From: Peter Zijlstra To: Boqun Feng Cc: torvalds@linux-foundation.org, keescook@chromium.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, 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, mingo@redhat.com, longman@redhat.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: Re: [PATCH v3 08/57] sched: Simplify wake_up_if_idle() Message-ID: <20230612200229.GN4253@hirez.programming.kicks-ass.net> References: <20230612090713.652690195@infradead.org> <20230612093537.977924652@infradead.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Jun 12, 2023 at 11:02:28AM -0700, Boqun Feng wrote: > On Mon, Jun 12, 2023 at 11:07:21AM +0200, Peter Zijlstra wrote: > > Use guards to reduce gotos and simplify control flow. > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/sched/core.c | 20 ++++++-------------- > > kernel/sched/sched.h | 15 +++++++++++++++ > > 2 files changed, 21 insertions(+), 14 deletions(-) > > > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct > > void wake_up_if_idle(int cpu) > > { > > struct rq *rq = cpu_rq(cpu); > > - struct rq_flags rf; > > > > - rcu_read_lock(); > > - > > - if (!is_idle_task(rcu_dereference(rq->curr))) > > - goto out; > > - > > - rq_lock_irqsave(rq, &rf); > > - if (is_idle_task(rq->curr)) > > - resched_curr(rq); > > - /* Else CPU is not idle, do nothing here: */ > > - rq_unlock_irqrestore(rq, &rf); > > - > > -out: > > - rcu_read_unlock(); > > + guard(rcu)(); > > + if (is_idle_task(rcu_dereference(rq->curr))) { > > + guard(rq_lock)(rq); > > We assume that irq must be disabled when this function called? > Otherwise, I don't understand why this is not > > guard(rq_lock_irqsave)(rq); > You're quite right, I messed that up.