From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753308AbbCQISS (ORCPT ); Tue, 17 Mar 2015 04:18:18 -0400 Received: from casper.infradead.org ([85.118.1.10]:47366 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752026AbbCQISP (ORCPT ); Tue, 17 Mar 2015 04:18:15 -0400 Date: Tue, 17 Mar 2015 09:18:07 +0100 From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, linux-api@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU Message-ID: <20150317081807.GQ2896@worktop.programming.kicks-ass.net> References: <20150316183743.GA21453@linux.vnet.ibm.com> <1426531086-23825-1-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1426531086-23825-1-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 16, 2015 at 11:37:45AM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > RCU ignores offlined CPUs, so they cannot safely run RCU read-side code. > (They -can- use SRCU, but not RCU.) This means that any use of RCU > during or after the call to arch_cpu_idle_dead(). Unfortunately, > commit 2ed53c0d6cc99 added a complete() call, which will contain RCU > read-side critical sections if there is a task waiting to be awakened. Got a little more detail there? From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU Date: Tue, 17 Mar 2015 09:18:07 +0100 Message-ID: <20150317081807.GQ2896@worktop.programming.kicks-ass.net> References: <20150316183743.GA21453@linux.vnet.ibm.com> <1426531086-23825-1-git-send-email-paulmck@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1426531086-23825-1-git-send-email-paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Paul E. McKenney" Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, laijs-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, dipankar-xthvdsQ13ZrQT0dZR+AlfA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, dvhart-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, bobby.prani-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On Mon, Mar 16, 2015 at 11:37:45AM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > RCU ignores offlined CPUs, so they cannot safely run RCU read-side code. > (They -can- use SRCU, but not RCU.) This means that any use of RCU > during or after the call to arch_cpu_idle_dead(). Unfortunately, > commit 2ed53c0d6cc99 added a complete() call, which will contain RCU > read-side critical sections if there is a task waiting to be awakened. Got a little more detail there?