diff options
| -rw-r--r-- | include/linux/hardirq.h | 24 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 6 | ||||
| -rw-r--r-- | include/linux/rcutiny.h | 97 | ||||
| -rw-r--r-- | init/Kconfig | 9 | ||||
| -rw-r--r-- | kernel/Makefile | 1 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 4 | ||||
| -rw-r--r-- | kernel/rcutiny.c | 294 |
7 files changed, 435 insertions, 0 deletions
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 6d527ee82b2b..d5b387669dab 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -139,10 +139,34 @@ static inline void account_system_vtime(struct task_struct *tsk) #endif #if defined(CONFIG_NO_HZ) +#if defined(CONFIG_TINY_RCU) +extern void rcu_enter_nohz(void); +extern void rcu_exit_nohz(void); + +static inline void rcu_irq_enter(void) +{ + rcu_exit_nohz(); +} + +static inline void rcu_irq_exit(void) +{ + rcu_enter_nohz(); +} + +static inline void rcu_nmi_enter(void) +{ +} + +static inline void rcu_nmi_exit(void) +{ +} + +#else extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); extern void rcu_nmi_enter(void); extern void rcu_nmi_exit(void); +#endif #else # define rcu_irq_enter() do { } while (0) # define rcu_irq_exit() do { } while (0) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3ebd0b7bcb08..6dd71fa48429 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -68,11 +68,17 @@ extern int sched_expedited_torture_stats(char *page); /* Internal to kernel */ extern void rcu_init(void); extern void rcu_scheduler_starting(void); +#ifndef CONFIG_TINY_RCU extern int rcu_needs_cpu(int cpu); +#else +static inline int rcu_needs_cpu(int cpu) { return 0; } +#endif extern int rcu_scheduler_active; #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include <linux/rcutree.h> +#elif CONFIG_TINY_RCU +#include <linux/rcutiny.h> #else #error "Unknown RCU implementation specified to kernel configuration" #endif diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h new file mode 100644 index 000000000000..891073c264dc --- /dev/null +++ b/include/linux/rcutiny.h @@ -0,0 +1,97 @@ +/* + * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright IBM Corporation, 2008 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ + +#ifndef __LINUX_TINY_H +#define __LINUX_TINY_H + +#include <linux/cache.h> + +void rcu_sched_qs(int cpu); +void rcu_bh_qs(int cpu); + +#define __rcu_read_lock() preempt_disable() +#define __rcu_read_unlock() preempt_enable() +#define __rcu_read_lock_bh() local_bh_disable() +#define __rcu_read_unlock_bh() local_bh_enable() +#define call_rcu_sched call_rcu + +#define rcu_init_sched() do { } while (0) +extern void rcu_check_callbacks(int cpu, int user); +extern void __rcu_init(void); + +/* + * Return the number of grace periods. + */ +static inline long rcu_batches_completed(void) +{ + return 0; +} + +/* + * Return the number of bottom-half grace periods. + */ +static inline long rcu_batches_completed_bh(void) +{ + return 0; +} + +extern int rcu_expedited_torture_stats(char *page); + +static inline void synchronize_rcu_expedited(void) +{ + synchronize_sched(); +} + +static inline void synchronize_rcu_bh_expedited(void) +{ + synchronize_sched(); +} + +struct notifier_block; +extern int rcu_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu); + +#ifdef CONFIG_NO_HZ + +extern void rcu_enter_nohz(void); +extern void rcu_exit_nohz(void); + +#else /* #ifdef CONFIG_NO_HZ */ + +static inline void rcu_enter_nohz(void) +{ +} + +static inline void rcu_exit_nohz(void) +{ +} + +#endif /* #else #ifdef CONFIG_NO_HZ */ + +static inline void exit_rcu(void) +{ +} + +#endif /* __LINUX_RCUTINY_H */ diff --git a/init/Kconfig b/init/Kconfig index 09c5c6431f42..d367bf6bcc34 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -334,6 +334,15 @@ config TREE_PREEMPT_RCU is also required. It also scales down nicely to smaller systems. +config TINY_RCU + bool "UP-only small-memory-footprint RCU" + depends on !SMP + help + This option selects the RCU implementation that is + designed for UP systems from which real-time response + is not required. This option greatly reduces the + memory footprint of RCU. + endchoice config RCU_TRACE diff --git a/kernel/Makefile b/kernel/Makefile index b8d4cd8ac0b9..e9a0e6ed25cc 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -82,6 +82,7 @@ obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o obj-$(CONFIG_TREE_RCU) += rcutree.o obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o +obj-$(CONFIG_TINY_RCU) += rcutiny.o obj-$(CONFIG_RELAY) += relay.o obj-$(CONFIG_SYSCTL) += utsname_sysctl.o obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 400183346ad2..7625f207f65e 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -67,6 +67,8 @@ void wakeme_after_rcu(struct rcu_head *head) complete(&rcu->completion); } +#ifndef CONFIG_TINY_RCU + #ifdef CONFIG_TREE_PREEMPT_RCU /** @@ -157,6 +159,8 @@ void synchronize_rcu_bh(void) } EXPORT_SYMBOL_GPL(synchronize_rcu_bh); +#endif /* #ifndef CONFIG_TINY_RCU */ + static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, unsigned long action, void *hcpu) { diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c new file mode 100644 index 000000000000..0b54efde66ac --- /dev/null +++ b/kernel/rcutiny.c @@ -0,0 +1,294 @@ +/* + * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright IBM Corporation, 2008 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/module.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/time.h> + +/* Global control variables for rcupdate callback mechanism. */ +struct rcu_ctrlblk { + struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ + struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ + struct rcu_head **curtail; /* ->next pointer of last CB. */ +}; + +/* Definition for rcupdate control block. */ +static struct rcu_ctrlblk rcu_ctrlblk = { + .rcucblist = NULL, + .donetail = &rcu_ctrlblk.rcucblist, + .curtail = &rcu_ctrlblk.rcucblist, +}; +static struct rcu_ctrlblk rcu_bh_ctrlblk = { + .rcucblist = NULL, + .donetail = &rcu_bh_ctrlblk.rcucblist, + .curtail = &rcu_bh_ctrlblk.rcucblist, +}; + +#ifdef CONFIG_NO_HZ + +static long rcu_dynticks_nesting = 1; + +/* + * Enter dynticks-idle mode, which is an extended quiescent state + * if we have fully entered that mode (i.e., if the new value of + * dynticks_nesting is zero). + */ +void rcu_enter_nohz(void) +{ + if (--rcu_dynticks_nesting == 0) + rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ +} + +/* + * Exit dynticks-idle mode, so that we are no longer in an extended + * quiescent state. + */ +void rcu_exit_nohz(void) +{ + rcu_dynticks_nesting++; +} + +#endif /* #ifdef CONFIG_NO_HZ */ + +/* + * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc(). + * Also disable irqs to avoid confusion due to interrupt handlers invoking + * call_rcu(). + */ +static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) +{ + unsigned long flags; + + local_irq_save(flags); + if (rcp->rcucblist != NULL && + rcp->donetail != rcp->curtail) { + rcp->donetail = rcp->curtail; + local_irq_restore(flags); + return 1; + } + local_irq_restore(flags); + return 0; +} + +/* + * Record an rcu quiescent state. And an rcu_bh quiescent state while we + * are at it, given that any rcu quiescent state is also an rcu_bh + * quiescent state. Use "+" instead of "||" to defeat short circuiting. + */ +void rcu_sched_qs(int cpu) +{ + if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); +} + +/* + * Record an rcu_bh quiescent state. + */ +void rcu_bh_qs(int cpu) +{ + if (rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); +} + +/* + * Check to see if the scheduling-clock interrupt came from an extended + * quiescent state, and, if so, tell RCU about it. + */ +void rcu_check_callbacks(int cpu, int user) +{ + if (user || + (idle_cpu(cpu) && + !in_softirq() && + hardirq_count() <= (1 << HARDIRQ_SHIFT))) + rcu_sched_qs(cpu); + else if (!in_softirq()) + rcu_bh_qs(cpu); +} + +/* + * Helper function for rcu_process_callbacks() that operates on the + * specified rcu_ctrlkblk structure. + */ +static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) +{ + unsigned long flags; + struct rcu_head *next, *list; + + /* If no RCU callbacks ready to invoke, just return. */ + if (&rcp->rcucblist == rcp->donetail) + return; + + /* Move the ready-to-invoke callbacks to a local list. */ + local_irq_save(flags); + list = rcp->rcucblist; + rcp->rcucblist = *rcp->donetail; + *rcp->donetail = NULL; + if (rcp->curtail == rcp->donetail) + rcp->curtail = &rcp->rcucblist; + rcp->donetail = &rcp->rcucblist; + local_irq_restore(flags); + + /* Invoke the callbacks on the local list. */ + while (list) { + next = list->next; + prefetch(next); + list->func(list); + list = next; + } +} + +/* + * Invoke any callbacks whose grace period has completed. + */ +static void rcu_process_callbacks(struct softirq_action *unused) +{ + __rcu_process_callbacks(&rcu_ctrlblk); + __rcu_process_callbacks(&rcu_bh_ctrlblk); +} + +/* + * Null function to handle CPU being onlined. Longer term, we want to + * make TINY_RCU avoid using rcupdate.c, but later... + */ +int rcu_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + return NOTIFY_OK; +} + +/* + * Wait for a grace period to elapse. But it is illegal to invoke + * synchronize_sched() from within an RCU read-side critical section. + * Therefore, any legal call to synchronize_sched() is a quiescent + * state, and so on a UP system, synchronize_sched() need do nothing. + * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the + * benefits of doing might_sleep() to reduce latency.) + * + * Cool, huh? (Due to Josh Triplett.) + * + * But we want to make this a static inline later. + */ +void synchronize_sched(void) +{ + cond_resched(); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + +void synchronize_rcu_bh(void) +{ + synchronize_sched(); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_bh); + +/* + * Helper function for call_rcu() and call_rcu_bh(). + */ +static void __call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu), + struct rcu_ctrlblk *rcp) +{ + unsigned long flags; + + head->func = func; + head->next = NULL; + local_irq_save(flags); + *rcp->curtail = head; + rcp->curtail = &head->next; + local_irq_restore(flags); +} + +/* + * Post an RCU callback to be invoked after the end of an RCU grace + * period. But since we have but one CPU, that would be after any + * quiescent state. + */ +void call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/* + * Post an RCU bottom-half callback to be invoked after any subsequent + * quiescent state. + */ +void call_rcu_bh(struct rcu_head *head, + void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_bh_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu_bh); + +void rcu_barrier(void) +{ + struct rcu_synchronize rcu; + + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +void rcu_barrier_bh(void) +{ + struct rcu_synchronize rcu; + + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_bh(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} +EXPORT_SYMBOL_GPL(rcu_barrier_bh); + +void rcu_barrier_sched(void) +{ + struct rcu_synchronize rcu; + + 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(rcu_barrier_sched); + +void __rcu_init(void) +{ + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); +} |