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Thu, 04 Feb 2021 14:52:58 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E12203003D8; Thu, 4 Feb 2021 15:52:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C22082138F7C4; Thu, 4 Feb 2021 15:52:53 +0100 (CET) Date: Thu, 4 Feb 2021 15:52:53 +0100 From: Peter Zijlstra To: "Joel Fernandes (Google)" Cc: Nishanth Aravamudan , Julien Desfossez , Tim Chen , Vineeth Pillai , Aaron Lu , Aubrey Li , tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , vineeth@bitbyteword.org, Chen Yu , Christian Brauner , Agata Gruza , Antonio Gomez Iglesias , graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com, pjt@google.com, rostedt@goodmis.org, derkling@google.com, benbjiang@tencent.com, Alexandre Chartre , James.Bottomley@hansenpartnership.com, OWeisse@umich.edu, Dhaval Giani , Junaid Shahid , jsbarnes@google.com, chris.hyser@oracle.com, Ben Segall , Josh Don , Hao Luo , Tom Lendacky Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core scheduling Message-ID: References: <20210123011704.1901835-1-joel@joelfernandes.org> <20210123011704.1901835-3-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210123011704.1901835-3-joel@joelfernandes.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 22, 2021 at 08:17:01PM -0500, Joel Fernandes (Google) wrote: > +static void sched_core_update_cookie(struct task_struct *p, unsigned long cookie, > + enum sched_core_cookie_type cookie_type) > +{ > + struct rq_flags rf; > + struct rq *rq; > + > + if (!p) > + return; > + > + rq = task_rq_lock(p, &rf); > + > + switch (cookie_type) { > + case sched_core_task_cookie_type: > + p->core_task_cookie = cookie; > + break; > + case sched_core_group_cookie_type: > + p->core_group_cookie = cookie; > + break; > + default: > + WARN_ON_ONCE(1); > + } > + > + /* Set p->core_cookie, which is the overall cookie */ > + __sched_core_update_cookie(p); > + > + if (sched_core_enqueued(p)) { > + sched_core_dequeue(rq, p); > + if (!p->core_cookie) { > + task_rq_unlock(rq, p, &rf); > + return; > + } > + } > + > + if (sched_core_enabled(rq) && > + p->core_cookie && task_on_rq_queued(p)) > + sched_core_enqueue(task_rq(p), p); > + > + /* > + * If task is currently running or waking, it may not be compatible > + * anymore after the cookie change, so enter the scheduler on its CPU > + * to schedule it away. > + */ > + if (task_running(rq, p) || p->state == TASK_WAKING) > + resched_curr(rq); I'm not immediately seeing the need for that WAKING test. Since we're holding it's rq->lock, the only place that task can be WAKING is on the wake_list. And if it's there, it needs to acquire rq->lock to get enqueued, and rq->lock again to get scheduled. What am I missing? > + > + task_rq_unlock(rq, p, &rf); > +}