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Open Source and information security mailing list archives
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Date: Tue, 1 Dec 2020 14:20:28 -0500 From: Joel Fernandes <joel@...lfernandes.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Nishanth Aravamudan <naravamudan@...italocean.com>, Julien Desfossez <jdesfossez@...italocean.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Vineeth Pillai <viremana@...ux.microsoft.com>, Aaron Lu <aaron.lwe@...il.com>, Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de, linux-kernel@...r.kernel.org, mingo@...nel.org, torvalds@...ux-foundation.org, fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com, Phil Auld <pauld@...hat.com>, Valentin Schneider <valentin.schneider@....com>, Mel Gorman <mgorman@...hsingularity.net>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Paolo Bonzini <pbonzini@...hat.com>, vineeth@...byteword.org, Chen Yu <yu.c.chen@...el.com>, Christian Brauner <christian.brauner@...ntu.com>, Agata Gruza <agata.gruza@...el.com>, Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>, graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com, pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com, benbjiang@...cent.com, Alexandre Chartre <alexandre.chartre@...cle.com>, James.Bottomley@...senpartnership.com, OWeisse@...ch.edu, Dhaval Giani <dhaval.giani@...cle.com>, Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com, chris.hyser@...cle.com, Ben Segall <bsegall@...gle.com>, Josh Don <joshdon@...gle.com>, Hao Luo <haoluo@...gle.com>, Tom Lendacky <thomas.lendacky@....com>, Aubrey Li <aubrey.li@...ux.intel.com>, "Paul E. McKenney" <paulmck@...nel.org>, Tim Chen <tim.c.chen@...el.com> Subject: Re: [PATCH -tip 22/32] sched: Split the cookie and setup per-task cookie on fork On Wed, Nov 25, 2020 at 12:10:14PM +0100, Peter Zijlstra wrote: > On Tue, Nov 17, 2020 at 06:19:52PM -0500, Joel Fernandes (Google) wrote: > > +void sched_core_tag_requeue(struct task_struct *p, unsigned long cookie, bool group) > > +{ > > + if (!p) > > + return; > > + > > + if (group) > > + p->core_group_cookie = cookie; > > + else > > + p->core_task_cookie = cookie; > > + > > + /* Use up half of the cookie's bits for task cookie and remaining for group cookie. */ > > + p->core_cookie = (p->core_task_cookie << > > + (sizeof(unsigned long) * 4)) + p->core_group_cookie; > > This seems dangerous; afaict there is nothing that prevents cookie > collision. This is fixed in a later patch by Josh "sched: Refactor core cookie into struct" where we are having independent fields for each type of cookie. I'll squash it next time I post to prevent confusion. Thanks, - Joel
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