From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757022AbbCCRlx (ORCPT ); Tue, 3 Mar 2015 12:41:53 -0500 Received: from e37.co.us.ibm.com ([32.97.110.158]:36567 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751617AbbCCRlv (ORCPT ); Tue, 3 Mar 2015 12:41:51 -0500 Date: Tue, 3 Mar 2015 09:41:44 -0800 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: [PATCH tip/core/rcu 0/20] CPU hotplug updates for v4.1 Message-ID: <20150303174144.GA13139@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15030317-0025-0000-0000-00000902328D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! This series updates RCU's handling of CPU hotplug offline operations, allowing RCU to have a precise notification of when it should start ignoring a CPU. This allowed detection of some illegal use of RCU by offline CPUs, and this series contains fixes for these. A similar problem exists for CPU onlining, but will be addressed later. One CPU-hotplug dragon at a time. 1. Add common code for notification from dying CPU. This is part of the fix for issues uncovered by improved detection, but is placed first to avoid messing up bisection. 2-4. Use #1 for x86, blackfin, and metag. (ARM also has this problem, but ARM's maintainers are working on their own fix.) 5. Remove duplicate offline-CPU callback-list initialization. This simplifies later changes to RCU's handling of offlining operations. 6. Improve code readability in rcu_cleanup_dead_cpu(). Simple code motion, no semantic change. 7. Eliminate a boolean variable and "if" statement by rearranging sync_rcu_preempt_exp_init()'s checks for CPUs not having blocked tasks. 8. Eliminate empty CONFIG_HOTPLUG_CPU #ifdef. 9. Add diagnostics to detect when RCU CPU stall warnings have been caused by failure to propagate quiescent states up the rcu_node combining tree. 10. Provide CONFIG_RCU_TORTURE_TEST_SLOW_INIT Kconfig option to artificially slow down grace-period initialization, thus increasing the probability of detecting races with this initialization process. 11. Update data files to enable CONFIG_RCU_TORTURE_TEST_SLOW_INIT by default during rcutorture testing, but leave the default time at zero. This default may be overridden by passing "--bootargs rcutree.gp_init_delay=1" to kvm.sh. 12. Remove event tracing from rcu_cpu_notify(), which is invoked by offline CPUs. (Event tracing uses RCU.) 13. Change meaning of ->expmask bitmasks to track blocked tasks rather than online CPUs. 14. Move rcu_report_unblock_qs_rnp() to common code. This will make it easier to provide proper locking protection. 15. Avoid races between CPU-hotplug operations and RCU grace-period initialization by processing CPU-hotplug changes only at the start of each grace period. This works because RCU need not wait on a CPU that came online after the start of the current grace period. 16. Eliminate the no-longer-needed ->onoff_mutex from the rcu_node structure. This is the only sleeplock acquired during RCU's CPU-hotplug processing, which in turn allows rcu_cpu_notify() to be invoked from the preemption-disabled idle loop. 17. Use a per-CPU variable to make the CPU-offline idle-loop transition point precise. (RCU's magic one-jiffy grace-period wait for offline CPUs must remain until the analogous online issue is addressed.) 18. Invoke rcu_cpu_notify() with a new CPU_DYING_IDLE op just before the idle-loop invocation of arch_cpu_idle_dead(). 19. Now that CPU-hotplug events are applied only during grace-period initialization, it is safe to unconditionally enable slow grace-period initialization for rcutorture testing. Note that this delay is applied randomly in order to get a good mix of fast and slow grace-period initialization. 20. Add checks that all quiescent states were received at grace-period cleanup time. Thanx, Paul ------------------------------------------------------------------------ b/Documentation/kernel-parameters.txt | 6 b/arch/blackfin/mach-common/smp.c | 6 b/arch/metag/kernel/smp.c | 5 b/arch/x86/include/asm/cpu.h | 2 b/arch/x86/include/asm/smp.h | 1 b/arch/x86/kernel/smpboot.c | 29 - b/arch/x86/xen/smp.c | 18 b/include/linux/cpu.h | 14 b/include/linux/rcupdate.h | 2 b/kernel/cpu.c | 4 b/kernel/rcu/tree.c | 279 ++++++++++---- b/kernel/rcu/tree.h | 11 b/kernel/rcu/tree_plugin.h | 121 +----- b/kernel/rcu/tree_trace.c | 4 b/kernel/sched/idle.c | 9 b/kernel/smpboot.c | 156 +++++++ b/lib/Kconfig.debug | 26 + b/tools/testing/selftests/rcutorture/configs/rcu/CFcommon | 1 18 files changed, 492 insertions(+), 202 deletions(-)