From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [PATCH v8 04/14] task_isolation: add initial support Date: Tue, 20 Oct 2015 20:29:29 -0400 Message-ID: <20151020202929.485a1ef0@grimm.local.home> References: <1445373372-6567-1-git-send-email-cmetcalf@ezchip.com> <1445373372-6567-5-git-send-email-cmetcalf@ezchip.com> <5626B00E.3010309@ezchip.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Andy Lutomirski Cc: Chris Metcalf , Gilad Ben Yossef , Ingo Molnar , Peter Zijlstra , Andrew Morton , Rik van Riel , Tejun Heo , Frederic Weisbecker , Thomas Gleixner , "Paul E. McKenney" , Christoph Lameter , Viresh Kumar , Catalin Marinas , Will Deacon , "linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Linux API , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-api@vger.kernel.org On Tue, 20 Oct 2015 14:26:34 -0700 Andy Lutomirski wrote: > I'm not a scheduler person, so I don't know. But "don't run me unless > I'm isolated" seems like a design that will, at best, only ever work > by dumb luck. You have to disable migration, avoid other runnable > tasks, hope that the kernel keeps working the way it did when you > wrote the patch, hope you continue to get lucky enough that you ever > get to user mode in the first place, etc. Since it only makes sense to run one isolated task per cpu (not more than one on the same CPU), I wonder if we should add a new interface for this, that would force everything else off the CPU that it requests. That is, you bind a task to a CPU, and then change it to SCHED_ISOLATED (or what not), and the kernel will force all other tasks off that CPU. Well, we would still have kernel threads, but that's a different matter. Also, doesn't RCU need to have a few ticks go by before it can safely disable itself from userspace? I recall something like that. Paul? -- Steve