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Mon, 12 Jun 2023 06:51:23 -0700 (PDT) Received: from localhost ([102.36.222.112]) by smtp.gmail.com with ESMTPSA id s12-20020a7bc38c000000b003f7ba52eeccsm11531482wmj.7.2023.06.12.06.51.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jun 2023 06:51:21 -0700 (PDT) Date: Mon, 12 Jun 2023 16:51:17 +0300 From: Dan Carpenter To: Peter Zijlstra 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: <0012d943-6fd0-4b8d-9ec6-3d02aba75dcc@kadam.mountain> References: <20230612090713.652690195@infradead.org> <20230612093538.076428270@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230612093538.076428270@infradead.org> Precedence: bulk List-ID: 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. > 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(); > } regards, dan carpenter