Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755066AbZIMQPl (ORCPT ); Sun, 13 Sep 2009 12:15:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754952AbZIMQPN (ORCPT ); Sun, 13 Sep 2009 12:15:13 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:44719 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754864AbZIMQPH (ORCPT ); Sun, 13 Sep 2009 12:15:07 -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, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 4/4] Fix synchronize_rcu() for TREE_PREEMPT_RCU Date: Sun, 13 Sep 2009 09:15:11 -0700 Message-Id: <12528585111916-git-send-email-> X-Mailer: git-send-email 1.5.2.5 In-Reply-To: <20090913161438.GA32550@linux.vnet.ibm.com> References: <20090913161438.GA32550@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paul E. McKenney The redirection of synchronize_sched() to synchronize_rcu() was appropriate for TREE_RCU, but not for TREE_PREEMPT_RCU. Fix this by creating an underlying synchronize_sched(). TREE_RCU then redirects synchronize_rcu() to synchronize_sched(), while TREE_PREEMPT_RCU has its own version of synchronize_rcu(). Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 23 +++++------------------ include/linux/rcutree.h | 4 ++-- kernel/rcupdate.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 50 insertions(+), 21 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 95e0615..39dce83 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -52,8 +52,13 @@ struct rcu_head { }; /* Exported common interfaces */ +#ifdef CONFIG_TREE_PREEMPT_RCU extern void synchronize_rcu(void); +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ +#define synchronize_rcu synchronize_sched +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ extern void synchronize_rcu_bh(void); +extern void synchronize_sched(void); extern void rcu_barrier(void); extern void rcu_barrier_bh(void); extern void rcu_barrier_sched(void); @@ -262,24 +267,6 @@ struct rcu_synchronize { extern void wakeme_after_rcu(struct rcu_head *head); /** - * synchronize_sched - block until all CPUs have exited any non-preemptive - * kernel code sequences. - * - * This means that all preempt_disable code sequences, including NMI and - * hardware-interrupt handlers, in progress on entry will have completed - * before this primitive returns. However, this does not guarantee that - * softirq handlers will have completed, since in some kernels, these - * handlers can run in process context, and can block. - * - * This primitive provides the guarantees made by the (now removed) - * synchronize_kernel() API. In contrast, synchronize_rcu() only - * guarantees that rcu_read_lock() sections will have completed. - * In "classic RCU", these two guarantees happen to be one and - * the same, but can differ in realtime RCU implementations. - */ -#define synchronize_sched() __synchronize_sched() - -/** * call_rcu - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual update function to be invoked after the grace period diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index a893077..00d08c0 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -53,6 +53,8 @@ static inline void __rcu_read_unlock(void) preempt_enable(); } +#define __synchronize_sched() synchronize_rcu() + static inline void exit_rcu(void) { } @@ -68,8 +70,6 @@ static inline void __rcu_read_unlock_bh(void) local_bh_enable(); } -#define __synchronize_sched() synchronize_rcu() - extern void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index bd5d5c8..28d2f24 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -74,6 +74,8 @@ void wakeme_after_rcu(struct rcu_head *head) complete(&rcu->completion); } +#ifdef CONFIG_TREE_PREEMPT_RCU + /** * synchronize_rcu - wait until a grace period has elapsed. * @@ -87,7 +89,7 @@ void synchronize_rcu(void) { struct rcu_synchronize rcu; - if (rcu_blocking_is_gp()) + if (!rcu_scheduler_active) return; init_completion(&rcu.completion); @@ -98,6 +100,46 @@ void synchronize_rcu(void) } EXPORT_SYMBOL_GPL(synchronize_rcu); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + +/** + * synchronize_sched - wait until an rcu-sched grace period has elapsed. + * + * Control will return to the caller some time after a full rcu-sched + * grace period has elapsed, in other words after all currently executing + * rcu-sched read-side critical sections have completed. These read-side + * critical sections are delimited by rcu_read_lock_sched() and + * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), + * local_irq_disable(), and so on may be used in place of + * rcu_read_lock_sched(). + * + * This means that all preempt_disable code sequences, including NMI and + * hardware-interrupt handlers, in progress on entry will have completed + * before this primitive returns. However, this does not guarantee that + * softirq handlers will have completed, since in some kernels, these + * handlers can run in process context, and can block. + * + * This primitive provides the guarantees made by the (now removed) + * synchronize_kernel() API. In contrast, synchronize_rcu() only + * guarantees that rcu_read_lock() sections will have completed. + * In "classic RCU", these two guarantees happen to be one and + * the same, but can differ in realtime RCU implementations. + */ +void synchronize_sched(void) +{ + struct rcu_synchronize rcu; + + if (rcu_blocking_is_gp()) + return; + + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_sched(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + /** * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. * -- 1.5.2.5 -- 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/