lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 27 Sep 2016 07:48:00 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Frederic Weisbecker <fweisbec@...il.com> Cc: Andy Lutomirski <luto@...capital.net>, Chris Metcalf <cmetcalf@...lanox.com>, Thomas Gleixner <tglx@...utronix.de>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, Christoph Lameter <cl@...ux.com>, Michal Hocko <mhocko@...e.com>, Gilad Ben Yossef <giladb@...lanox.com>, Andrew Morton <akpm@...ux-foundation.org>, Viresh Kumar <viresh.kumar@...aro.org>, Linux API <linux-api@...r.kernel.org>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>, Rik van Riel <riel@...hat.com>, Will Deacon <will.deacon@....com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Catalin Marinas <catalin.marinas@....com>, Peter Zijlstra <peterz@...radead.org> Subject: Re: [PATCH v15 04/13] task_isolation: add initial support On Tue, Sep 27, 2016 at 04:22:20PM +0200, Frederic Weisbecker wrote: > On Fri, Sep 02, 2016 at 10:28:00AM -0700, Andy Lutomirski wrote: > > > > Unless I'm missing something (which is reasonably likely), couldn't > > the isolation code just force or require rcu_nocbs on the isolated > > CPUs to avoid this problem entirely. > > rcu_nocb is already implied by nohz_full. Which means that RCU callbacks > are offlined outside the nohz_full set of CPUs. Indeed, at boot time, RCU makes any nohz_full CPU also be a rcu_nocb CPU. > > I admit I still don't understand why the RCU context tracking code > > can't just run the callback right away instead of waiting however many > > microseconds in general. I feel like paulmck has explained it to me > > at least once, but that doesn't mean I remember the answer. > > The RCU context tracking doesn't take care of callbacks. It's only there > to tell the RCU core whether the CPU runs code that may or may not run > RCU read side critical sections. This is assumed by "kernel may use RCU, > userspace can't". And RCU has to wait for read-side critical sections to complete before invoking callbacks. Thanx, Paul
Powered by blists - more mailing lists