Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754007AbbBTFKQ (ORCPT ); Fri, 20 Feb 2015 00:10:16 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:40807 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920AbbBTFJs (ORCPT ); Fri, 20 Feb 2015 00:09:48 -0500 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, "Paul E. McKenney" Subject: [PATCH v2 RFC tip/core/rcu 1/4] rcu: Provide rcu_expedite_gp() and rcu_unexpedite_gp() Date: Thu, 19 Feb 2015 21:09:36 -0800 Message-Id: <1424408979-1012-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <20150220050850.GA32639@linux.vnet.ibm.com> References: <20150220050850.GA32639@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15022005-0005-0000-0000-000008F1F795 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3492 Lines: 114 From: "Paul E. McKenney" Currently, expediting of normal synchronous grace-period primitives (synchronize_rcu() and friends) is controlled by the rcu_expedited() boot/sysfs parameter. This works well, but does not handle nesting. This commit therefore provides rcu_expedite_gp() to enable expediting and rcu_unexpedite_gp() to cancel a prior rcu_expedite_gp(), both of which support nesting. Reported-by: Arjan van de Ven Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 20 ++++++++++++++++++++ kernel/rcu/update.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 68 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9d3d0e1d0766..0189ac088c67 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -48,6 +48,26 @@ extern int rcu_expedited; /* for sysctl */ +#ifdef CONFIG_TINY_RCU +/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ +static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */ +{ + return false; +} + +static inline void rcu_expedite_gp(void) +{ +} + +static inline void rcu_unexpedite_gp(void) +{ +} +#else /* #ifdef CONFIG_TINY_RCU */ +bool rcu_gp_is_expedited(void); /* Internal RCU use. */ +void rcu_expedite_gp(void); +void rcu_unexpedite_gp(void); +#endif /* #else #ifdef CONFIG_TINY_RCU */ + enum rcutorture_type { RCU_FLAVOR, RCU_BH_FLAVOR, diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 8864ed90f0d7..44a74c24936a 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -62,6 +62,54 @@ MODULE_ALIAS("rcupdate"); module_param(rcu_expedited, int, 0); +#ifndef CONFIG_TINY_RCU + +static atomic_t rcu_expedited_nesting; + +/* + * Should normal grace-period primitives be expedited? Intended for + * use within RCU. Note that this function takes the rcu_expedited + * sysfs/boot variable into account as well as the rcu_expedite_gp() + * nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited() + * returns false is a -really- bad idea. + */ +bool rcu_gp_is_expedited(void) +{ + return rcu_expedited || atomic_read(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); + +/** + * rcu_expedite_gp - Expedite future RCU grace periods + * + * After a call to this function, future calls to synchronize_rcu() and + * friends act as the corresponding synchronize_rcu_expedited() function + * had instead been called. + */ +void rcu_expedite_gp(void) +{ + atomic_inc(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_expedite_gp); + +/** + * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation + * + * Undo a prior call to rcu_expedite_gp(). If all prior calls to + * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), + * and if the rcu_expedited sysfs/boot parameter is not set, then all + * subsequent calls to synchronize_rcu() and friends will return to + * their normal non-expedited behavior. + */ +void rcu_unexpedite_gp(void) +{ + atomic_dec(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); + +#endif /* #ifndef CONFIG_TINY_RCU */ + + #ifdef CONFIG_PREEMPT_RCU /* -- 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/