From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757336Ab0JUDZF (ORCPT ); Wed, 20 Oct 2010 23:25:05 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:57122 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1757083Ab0JUDZD (ORCPT ); Wed, 20 Oct 2010 23:25:03 -0400 Message-ID: <4CBFB381.50601@cn.fujitsu.com> Date: Thu, 21 Oct 2010 11:29:05 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100423 Thunderbird/3.0.4 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Ingo Molnar , LKML Subject: Re: [PATCH 1/2 v2] rcu,cleanup: move synchronize_sched_expedited() out of sched.c References: <4CBE886A.7010509@cn.fujitsu.com> <20101020191512.GG2386@linux.vnet.ibm.com> <20101021001928.GA24855@linux.vnet.ibm.com> In-Reply-To: <20101021001928.GA24855@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/21/2010 08:19 AM, Paul E. McKenney wrote: > On Wed, Oct 20, 2010 at 12:15:12PM -0700, Paul E. McKenney wrote: >> On Wed, Oct 20, 2010 at 02:12:58PM +0800, Lai Jiangshan wrote: >>> The first version of synchronize_sched_expedited() use the migration code >>> of the scheduler code, so it have to be implemented in sched.c >>> >>> but now, the synchronize_sched_expedited() does not use such code, >>> it is time to move it out of sched.c. >>> >>> Different rcu implementation' synchronize_sched_expedited() are also >>> different. so we move synchronize_sched_expedited() to kernel/rcutree_plugin.h >>> or include/linux/rcutiny.h instead of kerenl/rcupdate.c >> >> Queued, thank you!!! > > Hello again, Lai, > > I hit the following build error during testing: > > kernel/built-in.o: In function `.synchronize_rcu_expedited': > (.text+0x787d8): undefined reference to `.synchronize_sched_expedited' > kernel/built-in.o:(.toc1+0x1fe0): undefined reference to `synchronize_sched_expedited' > > This build uses defconfig with the following applied: > > CONFIG_RCU_TRACE=y > CONFIG_RCU_FAST_NO_HZ=y > CONFIG_NO_HZ=y > CONFIG_RCU_CPU_STALL_DETECTOR=y > CONFIG_SMP=y > CONFIG_RCU_FANOUT=8 > CONFIG_NR_CPUS=8 > CONFIG_RCU_FANOUT_EXACT=n > CONFIG_HOTPLUG_CPU=y > CONFIG_PREEMPT_NONE=y > CONFIG_PREEMPT_VOLUNTARY=n > CONFIG_PREEMPT=n > CONFIG_TREE_RCU=y > CONFIG_TREE_PREEMPT_RCU=n > CONFIG_RCU_TORTURE_TEST=m > CONFIG_MODULE_UNLOAD=y > CONFIG_SYSFS_DEPRECATED_V2=y > CONFIG_IKCONFIG=y > CONFIG_IKCONFIG_PROC=y > > Thoughts? > > Thanx, Paul > > I moved the code into CONFIG_TREE_PREEMPT_RCU=y codes. fixed version: Signed-off-by: Lai Jiangshan --- diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 0d0b640..ead36da 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -66,7 +66,6 @@ extern void call_rcu_sched(struct rcu_head *head, extern void synchronize_sched(void); extern void rcu_barrier_bh(void); extern void rcu_barrier_sched(void); -extern void synchronize_sched_expedited(void); extern int sched_expedited_torture_stats(char *page); static inline void __rcu_read_lock_bh(void) diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 13877cb..4d84452 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -58,6 +58,11 @@ static inline void synchronize_rcu_bh_expedited(void) synchronize_sched(); } +static inline void synchronize_sched_expedited(void) +{ + synchronize_sched(); +} + #ifdef CONFIG_TINY_RCU static inline void rcu_preempt_note_context_switch(void) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 95518e6..9a1fd6c 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -47,6 +47,7 @@ static inline void exit_rcu(void) #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ extern void synchronize_rcu_bh(void); +extern void synchronize_sched_expedited(void); extern void synchronize_rcu_expedited(void); static inline void synchronize_rcu_bh_expedited(void) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 0e75d60..0de359b 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -25,6 +25,7 @@ */ #include +#include /* * Check the RCU kernel configuration parameters and print informative @@ -1014,6 +1015,76 @@ static void __init __rcu_init_preempt(void) #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ +#ifndef CONFIG_SMP + +void synchronize_sched_expedited(void) +{ + cond_resched(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#else /* #ifndef CONFIG_SMP */ + +static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0); + +static int synchronize_sched_expedited_cpu_stop(void *data) +{ + /* + * There must be a full memory barrier on each affected CPU + * between the time that try_stop_cpus() is called and the + * time that it returns. + * + * In the current initial implementation of cpu_stop, the + * above condition is already met when the control reaches + * this point and the following smp_mb() is not strictly + * necessary. Do smp_mb() anyway for documentation and + * robustness against future implementation changes. + */ + smp_mb(); /* See above comment block. */ + return 0; +} + +/* + * Wait for an rcu-sched grace period to elapse, but use "big hammer" + * approach to force grace period to end quickly. This consumes + * significant time on all CPUs, and is thus not recommended for + * any sort of common-case code. + * + * Note that it is illegal to call this function while holding any + * lock that is acquired by a CPU-hotplug notifier. Failing to + * observe this restriction will result in deadlock. + */ +void synchronize_sched_expedited(void) +{ + int snap, trycount = 0; + + smp_mb(); /* ensure prior mod happens before capturing snap. */ + snap = atomic_read(&synchronize_sched_expedited_count) + 1; + get_online_cpus(); + while (try_stop_cpus(cpu_online_mask, + synchronize_sched_expedited_cpu_stop, + NULL) == -EAGAIN) { + put_online_cpus(); + if (trycount++ < 10) + udelay(trycount * num_online_cpus()); + else { + synchronize_sched(); + return; + } + if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) { + smp_mb(); /* ensure test happens before caller kfree */ + return; + } + get_online_cpus(); + } + atomic_inc(&synchronize_sched_expedited_count); + smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */ + put_online_cpus(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#endif /* #else #ifndef CONFIG_SMP */ + #if !defined(CONFIG_RCU_FAST_NO_HZ) /* diff --git a/kernel/sched.c b/kernel/sched.c index abf8440..9dc7775 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -9332,72 +9332,3 @@ struct cgroup_subsys cpuacct_subsys = { }; #endif /* CONFIG_CGROUP_CPUACCT */ -#ifndef CONFIG_SMP - -void synchronize_sched_expedited(void) -{ - barrier(); -} -EXPORT_SYMBOL_GPL(synchronize_sched_expedited); - -#else /* #ifndef CONFIG_SMP */ - -static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0); - -static int synchronize_sched_expedited_cpu_stop(void *data) -{ - /* - * There must be a full memory barrier on each affected CPU - * between the time that try_stop_cpus() is called and the - * time that it returns. - * - * In the current initial implementation of cpu_stop, the - * above condition is already met when the control reaches - * this point and the following smp_mb() is not strictly - * necessary. Do smp_mb() anyway for documentation and - * robustness against future implementation changes. - */ - smp_mb(); /* See above comment block. */ - return 0; -} - -/* - * Wait for an rcu-sched grace period to elapse, but use "big hammer" - * approach to force grace period to end quickly. This consumes - * significant time on all CPUs, and is thus not recommended for - * any sort of common-case code. - * - * Note that it is illegal to call this function while holding any - * lock that is acquired by a CPU-hotplug notifier. Failing to - * observe this restriction will result in deadlock. - */ -void synchronize_sched_expedited(void) -{ - int snap, trycount = 0; - - smp_mb(); /* ensure prior mod happens before capturing snap. */ - snap = atomic_read(&synchronize_sched_expedited_count) + 1; - get_online_cpus(); - while (try_stop_cpus(cpu_online_mask, - synchronize_sched_expedited_cpu_stop, - NULL) == -EAGAIN) { - put_online_cpus(); - if (trycount++ < 10) - udelay(trycount * num_online_cpus()); - else { - synchronize_sched(); - return; - } - if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) { - smp_mb(); /* ensure test happens before caller kfree */ - return; - } - get_online_cpus(); - } - atomic_inc(&synchronize_sched_expedited_count); - smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */ - put_online_cpus(); -} -EXPORT_SYMBOL_GPL(synchronize_sched_expedited); - -#endif /* #else #ifndef CONFIG_SMP */