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Fri, 05 Feb 2021 11:42:03 +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 9EB26301CC4; Fri, 5 Feb 2021 12:41:58 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 81A162BBE1CB0; Fri, 5 Feb 2021 12:41:58 +0100 (CET) Date: Fri, 5 Feb 2021 12:41:58 +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: > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -736,6 +736,7 @@ void __put_task_struct(struct task_struct *tsk) > exit_creds(tsk); > delayacct_tsk_free(tsk); > put_signal_struct(tsk->signal); > + sched_tsk_free(tsk); > > if (!profile_handoff_task(tsk)) > free_task(tsk); > +struct sched_core_task_cookie { > + refcount_t refcnt; > + struct work_struct work; /* to free in WQ context. */; > +}; > +static void sched_core_put_cookie_work(struct work_struct *ws); > + > +/* Caller has to call sched_core_get() if non-zero value is returned. */ > +static unsigned long sched_core_alloc_task_cookie(void) > +{ > + struct sched_core_task_cookie *ck = > + kmalloc(sizeof(struct sched_core_task_cookie), GFP_KERNEL); > + > + if (!ck) > + return 0; > + refcount_set(&ck->refcnt, 1); > + INIT_WORK(&ck->work, sched_core_put_cookie_work); > + > + return (unsigned long)ck; > +} > +static void sched_core_put_task_cookie(unsigned long cookie) > +{ > + struct sched_core_task_cookie *ptr = > + (struct sched_core_task_cookie *)cookie; > + > + if (refcount_dec_and_test(&ptr->refcnt)) > + kfree(ptr); > +} > +static void sched_core_put_cookie_work(struct work_struct *ws) > +{ > + struct sched_core_task_cookie *ck = > + container_of(ws, struct sched_core_task_cookie, work); > + > + sched_core_put_task_cookie((unsigned long)ck); > + sched_core_put(); > +} > +void sched_tsk_free(struct task_struct *tsk) > +{ > + struct sched_core_task_cookie *ck; > + > + sched_core_put_cookie((struct sched_core_cookie *)tsk->core_cookie); > + > + if (!tsk->core_task_cookie) > + return; > + > + ck = (struct sched_core_task_cookie *)tsk->core_task_cookie; > + queue_work(system_wq, &ck->work); > +} *groan*.. so the purpose of that work is to be able to disable core-scheduling after the last such task dies. Maybe add sched_core_put_async() instead?