From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751912AbdBFMr4 (ORCPT ); Mon, 6 Feb 2017 07:47:56 -0500 Received: from mout.gmx.net ([212.227.17.20]:60872 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750997AbdBFMrz (ORCPT ); Mon, 6 Feb 2017 07:47:55 -0500 Message-ID: <1486385257.10462.57.camel@gmx.de> Subject: Re: tip: demise of tsk_cpus_allowed() and tsk_nr_cpus_allowed() From: Mike Galbraith To: Ingo Molnar Cc: Ingo Molnar , Thomas Gleixner , Sebastian Andrzej Siewior , LKML , Peter Zijlstra Date: Mon, 06 Feb 2017 13:47:37 +0100 In-Reply-To: <20170206122928.GB9404@gmail.com> References: <1486355037.10462.17.camel@gmx.de> <20170206103156.GA18908@gmail.com> <1486383511.10462.43.camel@gmx.de> <20170206122928.GB9404@gmail.com> Content-Type: text/plain; charset="us-ascii" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:cOj0p4ZCbtfccIJA29qNy6RKbUHr2cuMzyNavvy8mQIHABwMjGv DT6IWjJU+CxE6+jSfsLO/AF6WFEBNCPUrKRWJKaXWAQsfOs4HoF5HgtdPoauTjJo/jNcrBR 8dsZwUu0vOMfdX7+4G7cfZWx7A83szePhZ5+VAVzjFTKoXDGcIrmVn/OrJkn6wYx3n4vXN+ dAbd1qRgT7SBClnij0UCg== X-UI-Out-Filterresults: notjunk:1;V01:K0:CA/KPVizp8k=:MZu3wbrgFnPjShKQNaK9nh mgkKOKaMkDW8ED5nfC3FAvEEmlCwyKVOwnx2BF7n5e8QMad6uHnWCTkJvORWNeRikwp7WZy4L 8xsvHvWbTEYdpvy1jBG/gI5iWglIBVCzEVrTZplmzZNBupU9dgS7mrLdCdt55Y2+sFKJb0ZvF 4PiCrQvTAurHPB1MJi1W7MZtISlQglgyyJSBat02c5RUuIFh9gycgVP3g3eDVM0K2rquu+AZ2 C9DlZ8eGD6Av/brqWIRqavOgHunZpJOxKgLAzo6YmzNo11i4bGW+t0gsd2IiyxqCW4y4TPpIQ 3HqgRYT9fLMnwpiIg0l47NMJnaKbGbehiIuRjacTnwedVBpxXNFlaW5iOlQqaO11nAzxuXGKq A5TJy7SvUbtzIoFh4sk5fCXZ3PkC6Oe056wM99sNl4XIcr/qW9r8VPyJ59sXrgn/eFoMil39V 2tIovHROWsRoEdSHpHPiW8Mh6ziXLC+sSOCqbVzhFtCkvDhbxw8Xyp3SRxZFH1B4VCD5laUOu YqtB2eEftzmnPPU5H2/L9Bj6vLV22RpKf9nk8BAPMg4y+fheYARKFKQcAmXLFwZ/Nk0OyoHdP SlX6pehxX//yCIuc6EL7oVlCz6lVakpdloSR2+ipLNMr+1Rpfbwy1GV9KjFKqtFXYsZoJtz8s p/ijgf7toYVUm0dKTmCGfUsFYVCUgkYSiz0p0qFpe0s4YC8Y8eoE0QJo4g2VEYR6/vfZtQA4Q oAwT5iSy/rCUIZ4c2m+R9BrVSM+xmmxM966HB1VtQQRFisoVnp3QR6PCBc38BoqdBYHVD6W9b wzSfVYf Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2017-02-06 at 13:29 +0100, Ingo Molnar wrote: > * Mike Galbraith wrote: > > > On Mon, 2017-02-06 at 11:31 +0100, Ingo Molnar wrote: > > > * Mike Galbraith wrote: > > > > > > > Hi Ingo, > > > > > > > > Doing my ~daily tip merge of -rt, I couldn't help noticing $subject, as > > > > they grow more functionality in -rt, which is allegedly slowly but > > > > surely headed toward merge. I don't suppose they could be left intact? > > > > I can easily restore them in my local tree, but it seems a bit of a > > > > shame to whack these integration friendly bits. > > > > > > Oh, I missed that. How is tsk_cpus_allowed() wrapped in -rt right now? > > > > RT extends them to reflect whether migration is disabled or not. > > > > +/* Future-safe accessor for struct task_struct's cpus_allowed. */ > > +static inline const struct cpumask *tsk_cpus_allowed(struct task_struct *p) > > +{ > > + if (__migrate_disabled(p)) > > + return cpumask_of(task_cpu(p)); > > + > > + return &p->cpus_allowed; > > +} > > + > > +static inline int tsk_nr_cpus_allowed(struct task_struct *p) > > +{ > > + if (__migrate_disabled(p)) > > + return 1; > > + return p->nr_cpus_allowed; > > +} > > So ... I think the cleaner approach in -rt would be to introduce > ->cpus_allowed_saved, and when disabling/enabling migration then saving the > current mask there and changing ->cpus_allowed - and then restoring it when > re-enabling migration. > > This means ->cpus_allowed could be used by the scheduler directly, no wrappery > would be required, AFAICS. > > ( Some extra care would be required in places that change ->cpus_allowed because > they'd now have to be aware of ->cpus_allowed_saved. ) > > Am I missing something? I suppose it's a matter of personal preference. I prefer the above, looks nice and clean to me. Hohum, I'll just put them back locally for the nonce. My trees are only place holders until official releases catch up anyway. -Mike