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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B87B3C88CB4 for ; Mon, 12 Jun 2023 14:08:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236972AbjFLOIy (ORCPT ); Mon, 12 Jun 2023 10:08:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232814AbjFLOIx (ORCPT ); Mon, 12 Jun 2023 10:08:53 -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 BA361E7B; Mon, 12 Jun 2023 07:08:51 -0700 (PDT) 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=0DnAgGwTA4yK+fgbpuGtXRFHoSZ33hlP/4ZXBRVYp+o=; b=E8ljFpn9WgTPZ/ghUHFMuqyFju 18HzrWeqfun7OJcAh9UGudekKNjDoGcljRZKBpo0giB5F3stC6nIUGSCxUkXXwyWbupj7TMNNuKil C0qZaWmsOGRDfcykSbtXyDsqwC53N/ffa90WzdfiGbg2Nf9pQCUWBGvK3g5jRwQH2YMDU8gyWl9pL ged32jUjfI4udvDbsKDUyg//e/7+o+wfbYlxZvJs2kevDwGt6B+NSKX3E7HM+/0Qg5oPE8qUAXM2V UaedKnuMQ1UooxP67PAFhoTXHLFIQzhWzWL98n3HOLUYZnu4gcQCoT2BpnYrDpylDyx4RZbFXxW4d S3FiX6nA==; 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 1q8iDt-008t8U-1b; Mon, 12 Jun 2023 14:08:45 +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 21FAB30058D; Mon, 12 Jun 2023 16:08:44 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id F09712BFD8191; Mon, 12 Jun 2023 16:08:43 +0200 (CEST) Date: Mon, 12 Jun 2023 16:08:43 +0200 From: Peter Zijlstra To: Dan Carpenter 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, 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: Re: [PATCH v3 09/57] sched: Simplify ttwu() Message-ID: <20230612140843.GZ83892@hirez.programming.kicks-ass.net> References: <20230612090713.652690195@infradead.org> <20230612093538.076428270@infradead.org> <0012d943-6fd0-4b8d-9ec6-3d02aba75dcc@kadam.mountain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0012d943-6fd0-4b8d-9ec6-3d02aba75dcc@kadam.mountain> Precedence: bulk List-ID: On Mon, Jun 12, 2023 at 04:51:17PM +0300, Dan Carpenter wrote: > On Mon, Jun 12, 2023 at 11:07:22AM +0200, Peter Zijlstra wrote: > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3664,16 +3664,15 @@ ttwu_stat(struct task_struct *p, int cpu > > __schedstat_inc(p->stats.nr_wakeups_local); > > } else { > > struct sched_domain *sd; > > + guard(rcu)(); > > > > __schedstat_inc(p->stats.nr_wakeups_remote); > > - rcu_read_lock(); > > We can't put the guard(rcu)(); here? I have unpublished static analysis > which assumes that the first and last statements guarded by a lock are > important. But if we always put it at the top of the scope then we > lose that information. we can definitely put it there. that one schedstat doesn't matter either way around. > > for_each_domain(rq->cpu, sd) { > > if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { > > __schedstat_inc(sd->ttwu_wake_remote); > > break; > > } > > } > > - rcu_read_unlock(); > > }