Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261851AbVDCSyz (ORCPT ); Sun, 3 Apr 2005 14:54:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261865AbVDCSyZ (ORCPT ); Sun, 3 Apr 2005 14:54:25 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:18088 "EHLO e6.ny.us.ibm.com") by vger.kernel.org with ESMTP id S261851AbVDCSyJ (ORCPT ); Sun, 3 Apr 2005 14:54:09 -0400 Date: Sun, 3 Apr 2005 11:54:15 -0700 From: "Paul E. McKenney" To: Michael Ellerman Cc: Linux Kernel list , dipankar@in.ibm.com, shemminger@osdl.org, manfred@colorfullife.com, bunk@stusta.de Subject: Re: [RFC,PATCH 2/4] Deprecate synchronize_kernel, GPL replacement Message-ID: <20050403185415.GC1481@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <20050403062149.GA1656@us.ibm.com> <200504040012.00616.michael@ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200504040012.00616.michael@ellerman.id.au> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5515 Lines: 143 On Mon, Apr 04, 2005 at 12:11:56AM +1000, Michael Ellerman wrote: > Hi Paul, > > I'm not quite clear on the difference between the two synchronize functions , > the comment for synchronize_sched() seems to have a bit missing? (see below) > > cheers > > On Sun, 3 Apr 2005 16:21, Paul E. McKenney wrote: > > +/** > > + * 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 > > ?? > > > + * > > + * This primitive provides the guarantees made by the (deprecated) > > + * synchronize_kernel() API. In contrast, synchronize_rcu() only > > + * guarantees that rcu_read_lock() sections will have completed. > > + */ > > +#define synchronize_sched() synchronize_rcu() Good catch! How about the following? + * 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 softirq + * handlers have completed, since some configs run them in process context. Updated patch below. Thanx, Paul Signed-off-by: diff -urpN -X dontdiff linux-2.6.12-rc1/include/linux/rcupdate.h linux-2.6.12-rc1-bettersk/include/linux/rcupdate.h --- linux-2.6.12-rc1/include/linux/rcupdate.h Tue Mar 1 23:37:50 2005 +++ linux-2.6.12-rc1-bettersk/include/linux/rcupdate.h Sat Apr 2 13:06:15 2005 @@ -41,6 +41,7 @@ #include #include #include +#include /** * struct rcu_head - callback structure for use with RCU @@ -157,9 +158,9 @@ static inline int rcu_pending(int cpu) /** * rcu_read_lock - mark the beginning of an RCU read-side critical section. * - * When synchronize_kernel() is invoked on one CPU while other CPUs + * When synchronize_rcu() is invoked on one CPU while other CPUs * are within RCU read-side critical sections, then the - * synchronize_kernel() is guaranteed to block until after all the other + * synchronize_rcu() is guaranteed to block until after all the other * CPUs exit their critical sections. Similarly, if call_rcu() is invoked * on one CPU while other CPUs are within RCU read-side critical * sections, invocation of the corresponding RCU callback is deferred @@ -256,6 +257,21 @@ static inline int rcu_pending(int cpu) (p) = (v); \ }) +/** + * 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 softirq + * handlers have completed, since some configs run them in process context. + * + * This primitive provides the guarantees made by the (deprecated) + * synchronize_kernel() API. In contrast, synchronize_rcu() only + * guarantees that rcu_read_lock() sections will have completed. + */ +#define synchronize_sched() synchronize_rcu() + extern void rcu_init(void); extern void rcu_check_callbacks(int cpu, int user); extern void rcu_restart_cpu(int cpu); @@ -265,7 +281,9 @@ extern void FASTCALL(call_rcu(struct rcu void (*func)(struct rcu_head *head))); extern void FASTCALL(call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head))); -extern void synchronize_kernel(void); +extern __deprecated_for_modules void synchronize_kernel(void); +extern void synchronize_rcu(void); +void synchronize_idle(void); #endif /* __KERNEL__ */ #endif /* __LINUX_RCUPDATE_H */ diff -urpN -X dontdiff linux-2.6.12-rc1/kernel/rcupdate.c linux-2.6.12-rc1-bettersk/kernel/rcupdate.c --- linux-2.6.12-rc1/kernel/rcupdate.c Tue Mar 1 23:37:30 2005 +++ linux-2.6.12-rc1-bettersk/kernel/rcupdate.c Sat Apr 2 13:10:09 2005 @@ -444,15 +444,18 @@ static void wakeme_after_rcu(struct rcu_ } /** - * synchronize_kernel - wait until a grace period has elapsed. + * synchronize_rcu - wait until a grace period has elapsed. * * Control will return to the caller some time after a full grace * period has elapsed, in other words after all currently executing RCU * read-side critical sections have completed. RCU read-side critical * sections are delimited by rcu_read_lock() and rcu_read_unlock(), * and may be nested. + * + * If your read-side code is not protected by rcu_read_lock(), do -not- + * use synchronize_rcu(). */ -void synchronize_kernel(void) +void synchronize_rcu(void) { struct rcu_synchronize rcu; @@ -464,7 +467,16 @@ void synchronize_kernel(void) wait_for_completion(&rcu.completion); } +/* + * Deprecated, use synchronize_rcu() or synchronize_sched() instead. + */ +void synchronize_kernel(void) +{ + synchronize_rcu(); +} + module_param(maxbatch, int, 0); EXPORT_SYMBOL(call_rcu); EXPORT_SYMBOL(call_rcu_bh); +EXPORT_SYMBOL_GPL(synchronize_rcu); EXPORT_SYMBOL(synchronize_kernel); - 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/