Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752171Ab3HTCsy (ORCPT ); Mon, 19 Aug 2013 22:48:54 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:35062 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752110Ab3HTCre (ORCPT ); Mon, 19 Aug 2013 22:47:34 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 9/9] nohz_full: Force RCU's grace-period kthreads onto timekeeping CPU Date: Mon, 19 Aug 2013 19:47:21 -0700 Message-Id: <1376966841-31774-9-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1376966841-31774-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20130820024700.GA31075@linux.vnet.ibm.com> <1376966841-31774-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13082002-2398-0000-0000-000001A4742B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3588 Lines: 99 From: "Paul E. McKenney" Because RCU's quiescent-state-forcing mechanism is used to drive the full-system-idle state machine, and because this mechanism is executed by RCU's grace-period kthreads, this commit forces these kthreads to run on the timekeeping CPU (tick_do_timer_cpu). To do otherwise would mean that the RCU grace-period kthreads would force the system into non-idle state every time they drove the state machine, which would be just a bit on the futile side. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt Cc: Lai Jiangshan Reviewed-by: Josh Triplett --- kernel/rcutree.c | 1 + kernel/rcutree.h | 1 + kernel/rcutree_plugin.h | 21 ++++++++++++++++++++- 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index eca70f44..64eaafb 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1303,6 +1303,7 @@ static int rcu_gp_init(struct rcu_state *rsp) struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(rsp); + rcu_bind_gp_kthread(); raw_spin_lock_irq(&rnp->lock); rsp->gp_flags = 0; /* Clear all flags: New grace period. */ diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 6fd3659..5f97eab 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -560,6 +560,7 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, static bool is_sysidle_rcu_state(struct rcu_state *rsp); static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, unsigned long maxj); +static void rcu_bind_gp_kthread(void); static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp); #endif /* #ifndef RCU_TREE_NONCORE */ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 90c3fba..dc7f0d4 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2531,7 +2531,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, if (!*isidle || rdp->rsp != rcu_sysidle_state || cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) return; - /* WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); */ + if (rcu_gp_in_progress(rdp->rsp)) + WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); /* Pick up current idle and NMI-nesting counter and check. */ cur = atomic_read(&rdtp->dynticks_idle); @@ -2557,6 +2558,20 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp) } /* + * Bind the grace-period kthread for the sysidle flavor of RCU to the + * timekeeping CPU. + */ +static void rcu_bind_gp_kthread(void) +{ + int cpu = ACCESS_ONCE(tick_do_timer_cpu); + + if (cpu < 0 || cpu >= nr_cpu_ids) + return; + if (raw_smp_processor_id() != cpu) + set_cpus_allowed_ptr(current, cpumask_of(cpu)); +} + +/* * Return a delay in jiffies based on the number of CPUs, rcu_node * leaf fanout, and jiffies tick rate. The idea is to allow larger * systems more time to transition to full-idle state in order to @@ -2754,6 +2769,10 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp) return false; } +static void rcu_bind_gp_kthread(void) +{ +} + static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, unsigned long maxj) { -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/