Hi,
Here is RCU for 2.5.34. It is just a rediff from earlier BK version.
The current rcu_poll is essentially a per-CPU version of the
rcu_poll patch in -aa series of kernel. Additionally it also supports
call_rcu_preempt() which allows RCU to work in preemptive kernels
transparently.
Ingo, it will be nice to have your comments on this, specially since
it touches the scheduler.
Read-Copy Update is also available in bk for pulling -
http://lse.bkbits.net/linux-2.5-rcu
Thanks
-- Dipankar Sarma <dipankar@in.ibm.com> http://lse.sourceforge.net Linux Technology Center, IBM Software Lab, Bangalore, India.diff -urN linux-2.5.34-base/include/linux/init_task.h linux-2.5.34-rcu_poll/include/linux/init_task.h --- linux-2.5.34-base/include/linux/init_task.h Mon Sep 9 23:05:02 2002 +++ linux-2.5.34-rcu_poll/include/linux/init_task.h Wed Sep 11 11:45:03 2002 @@ -83,6 +83,7 @@ .alloc_lock = SPIN_LOCK_UNLOCKED, \ .switch_lock = SPIN_LOCK_UNLOCKED, \ .journal_info = NULL, \ + .cpu_preempt_cntr = NULL, \ } diff -urN linux-2.5.34-base/include/linux/rcupdate.h linux-2.5.34-rcu_poll/include/linux/rcupdate.h --- linux-2.5.34-base/include/linux/rcupdate.h Thu Jan 1 05:30:00 1970 +++ linux-2.5.34-rcu_poll/include/linux/rcupdate.h Wed Sep 11 11:45:03 2002 @@ -0,0 +1,86 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * 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 (c) IBM Corporation, 2001 + * + * Author: Dipankar Sarma <dipankar@in.ibm.com> + * + * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com> + * and inputs from Andrea Arcangeli, Rusty Russell, Andi Kleen etc. + * Papers: + * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf + * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) + * + * For detailed explanation of Read-Copy Update mechanism see - + * http://lse.sourceforge.net/locking/rcupdate.html + * + */ + +#ifndef _LINUX_RCUPDATE_H +#define _LINUX_RCUPDATE_H + +#ifdef __KERNEL__ + +#include <linux/list.h> +#include <linux/spinlock.h> + +/** + * struct rcu_head - callback structure for use with RCU + * @list: list_head to queue the update requests + * @func: actual update function to call after the grace period. + * @arg: argument to be passed to the actual update function. + */ +struct rcu_head { + struct list_head list; + void (*func)(void *obj); + void *arg; +}; + +#define RCU_HEAD_INIT(head) \ + {.list = LIST_HEAD_INIT((head).list), .func = NULL, .arg = NULL} +#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head) +#define INIT_RCU_HEAD(ptr) do { \ + INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \ +} while (0) + +extern void FASTCALL(call_rcu(struct rcu_head *head, + void (*func)(void *arg), void *arg)); + +#ifdef CONFIG_PREEMPT + +#define rcu_read_lock() preempt_disable() +#define rcu_read_unlock() preempt_enable() +extern void FASTCALL(call_rcu_preempt(struct rcu_head *head, + void (*func)(void *arg), void *arg)); + +#else + +#define rcu_read_lock() do {} while(0) +#define rcu_read_unlock() do {} while(0) +static inline void call_rcu_preempt(struct rcu_head *head, + void (*func)(void *arg), void *arg) +{ + call_rcu(head, func, arg); +} + +#endif + +extern void synchronize_kernel(void); +extern void rcu_init(void); + +#endif /* __KERNEL__ */ +#endif /* _LINUX_RCUPDATE_H */ diff -urN linux-2.5.34-base/include/linux/sched.h linux-2.5.34-rcu_poll/include/linux/sched.h --- linux-2.5.34-base/include/linux/sched.h Mon Sep 9 23:05:02 2002 +++ linux-2.5.34-rcu_poll/include/linux/sched.h Wed Sep 11 11:45:03 2002 @@ -27,6 +27,7 @@ #include <linux/securebits.h> #include <linux/fs_struct.h> #include <linux/compiler.h> +#include <linux/percpu.h> struct exec_domain; @@ -164,6 +165,7 @@ extern void flush_scheduled_tasks(void); extern int start_context_thread(void); extern int current_is_keventd(void); +extern void force_cpu_reschedule(int cpu); struct namespace; @@ -383,6 +385,7 @@ /* journalling filesystem info */ void *journal_info; struct dentry *proc_dentry; + atomic_t *cpu_preempt_cntr; }; extern void __put_task_struct(struct task_struct *tsk); @@ -459,6 +462,8 @@ extern struct task_struct init_task; extern struct mm_struct init_mm; +extern struct task_struct *init_tasks[NR_CPUS]; +extern DEFINE_PER_CPU(long, cpu_quiescent); /* PID hashing. (shouldnt this be dynamic?) */ #define PIDHASH_SZ 8192 @@ -962,6 +967,55 @@ #endif /* CONFIG_SMP */ +#ifdef CONFIG_PREEMPT + +extern DEFINE_PER_CPU(atomic_t[2], rcu_preempt_cntr); +extern DEFINE_PER_CPU(atomic_t, *curr_preempt_cntr); +extern DEFINE_PER_CPU(atomic_t, *next_preempt_cntr); + +static inline void rcu_switch_preempt_cntr(int cpu) +{ + atomic_t *tmp; + tmp = per_cpu(curr_preempt_cntr, cpu); + per_cpu(curr_preempt_cntr, cpu) = per_cpu(next_preempt_cntr, cpu); + per_cpu(next_preempt_cntr, cpu) = tmp; + +} + +static inline void rcu_preempt_put(void) +{ + preempt_disable(); + if (unlikely(current->cpu_preempt_cntr != NULL)) { + atomic_dec(current->cpu_preempt_cntr); + current->cpu_preempt_cntr = NULL; + } + preempt_enable(); +} + +/* Must not be preempted */ +static inline void rcu_preempt_get(void) +{ + if (likely(current->cpu_preempt_cntr == NULL)) { + current->cpu_preempt_cntr = + per_cpu(next_preempt_cntr, smp_processor_id()); + atomic_inc(current->cpu_preempt_cntr); + } +} + +static inline int is_rcu_cpu_preempted(int cpu) +{ + return (atomic_read(per_cpu(curr_preempt_cntr, cpu)) != 0); +} +#else + +#define rcu_init_preempt_cntr(cpu) do { } while(0) +#define rcu_switch_preempt_cntr(cpu) do { } while(0) +#define rcu_preempt_put() do { } while(0) +#define rcu_preempt_get() do { } while(0) +#define is_rcu_cpu_preempted(cpu) (0) + +#endif + #endif /* __KERNEL__ */ #endif diff -urN linux-2.5.34-base/init/main.c linux-2.5.34-rcu_poll/init/main.c --- linux-2.5.34-base/init/main.c Mon Sep 9 23:05:04 2002 +++ linux-2.5.34-rcu_poll/init/main.c Wed Sep 11 11:45:03 2002 @@ -30,6 +30,7 @@ #include <linux/percpu.h> #include <linux/kernel_stat.h> #include <linux/security.h> +#include <linux/rcupdate.h> #include <asm/io.h> #include <asm/bugs.h> @@ -399,6 +400,7 @@ printk("Kernel command line: %s\n", saved_command_line); parse_options(command_line); trap_init(); + rcu_init(); init_IRQ(); sched_init(); softirq_init(); diff -urN linux-2.5.34-base/kernel/Makefile linux-2.5.34-rcu_poll/kernel/Makefile --- linux-2.5.34-base/kernel/Makefile Mon Sep 9 23:05:05 2002 +++ linux-2.5.34-rcu_poll/kernel/Makefile Wed Sep 11 11:45:03 2002 @@ -10,12 +10,12 @@ O_TARGET := kernel.o export-objs = signal.o sys.o kmod.o context.o ksyms.o pm.o exec_domain.o \ - printk.o platform.o suspend.o dma.o + printk.o platform.o suspend.o dma.o rcupdate.o obj-y = sched.o fork.o exec_domain.o panic.o printk.o \ module.o exit.o itimer.o time.o softirq.o resource.o \ sysctl.o capability.o ptrace.o timer.o user.o \ - signal.o sys.o kmod.o context.o futex.o platform.o + signal.o sys.o kmod.o context.o futex.o platform.o rcupdate.o obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o obj-$(CONFIG_SMP) += cpu.o diff -urN linux-2.5.34-base/kernel/exit.c linux-2.5.34-rcu_poll/kernel/exit.c --- linux-2.5.34-base/kernel/exit.c Mon Sep 9 23:05:07 2002 +++ linux-2.5.34-rcu_poll/kernel/exit.c Wed Sep 11 11:45:03 2002 @@ -616,6 +616,7 @@ preempt_disable(); if (current->exit_signal == -1) release_task(current); + rcu_preempt_put(); schedule(); BUG(); /* diff -urN linux-2.5.34-base/kernel/fork.c linux-2.5.34-rcu_poll/kernel/fork.c --- linux-2.5.34-base/kernel/fork.c Mon Sep 9 23:05:02 2002 +++ linux-2.5.34-rcu_poll/kernel/fork.c Wed Sep 11 11:45:03 2002 @@ -155,6 +155,7 @@ tsk->thread_info = ti; ti->task = tsk; atomic_set(&tsk->usage,1); + tsk->cpu_preempt_cntr = NULL; return tsk; } diff -urN linux-2.5.34-base/kernel/rcupdate.c linux-2.5.34-rcu_poll/kernel/rcupdate.c --- linux-2.5.34-base/kernel/rcupdate.c Thu Jan 1 05:30:00 1970 +++ linux-2.5.34-rcu_poll/kernel/rcupdate.c Wed Sep 11 13:20:52 2002 @@ -0,0 +1,294 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * 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 (c) IBM Corporation, 2001 + * Copyright (C) Andrea Arcangeli <andrea@suse.de> SuSE, 2001 + * + * Author: Dipankar Sarma <dipankar@in.ibm.com>, + * Andrea Arcangeli <andrea@suse.de> + * + * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com> + * and inputs from Andrea Arcangeli, Rusty Russell, Andi Kleen etc. + * Papers: + * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf + * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) + * + * For detailed explanation of Read-Copy Update mechanism see - + * http://lse.sourceforge.net/locking/rcupdate.html + * + */ + +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/spinlock.h> +#include <linux/sched.h> +#include <linux/smp.h> +#include <linux/interrupt.h> +#include <linux/module.h> +#include <linux/completion.h> +#include <linux/percpu.h> +#include <linux/rcupdate.h> + +struct rcu_data { + struct list_head nxtlist; + struct list_head curlist; + struct tasklet_struct tasklet; + unsigned long qsmask; + int polling; + long qcheckpt[NR_CPUS]; +} ____cacheline_aligned_in_smp; + +static struct rcu_data rcu_data[NR_CPUS] __cacheline_aligned; +static void rcu_data_init(struct rcu_data *); + +#ifdef CONFIG_PREEMPT +static spinlock_t rcu_lock_preempt = SPIN_LOCK_UNLOCKED; +static struct rcu_data rcu_data_preempt __cacheline_aligned; +static inline void rcu_preempt_lock(void) +{ + spin_lock_bh(&rcu_lock_preempt); +} +static inline void rcu_preempt_unlock(void) +{ + spin_unlock_bh(&rcu_lock_preempt); +} +static inline void rcu_data_preempt_init(void) +{ + rcu_data_init(&rcu_data_preempt); +} +#define is_rcu_preempt_data(rdata) (rdata == &rcu_data_preempt) +#else +static inline void rcu_preempt_lock(void) {} +static inline void rcu_preempt_unlock(void) {} +static inline void rcu_data_preempt_init(void) {} +#define is_rcu_preempt_data(rdata) (0) +#endif + +#define RCU_quiescent(cpu) per_cpu(cpu_quiescent, cpu) + +/** + * call_rcu - Queue an RCU update request. + * @head: structure to be used for queueing the RCU updates. + * @func: actual update function to be invoked after the grace period + * @arg: argument to be passed to the update function + * + * The update function will be invoked as soon as all CPUs have performed a + * context switch or been seen in the idle loop or in a user process. + * It can be called only from process or BH context, however can be + * made to work from irq context too with minor code changes + * if necessary. The read-side of critical section that use + * call_rcu() for updation must be protected by + * rcu_read_lock()/rcu_read_unlock(). + */ +void call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg) +{ + struct rcu_data *rdata; + + head->func = func; + head->arg = arg; + rdata = &rcu_data[get_cpu()]; + local_bh_disable(); + list_add(&head->list, &rdata->nxtlist); + local_bh_enable(); + tasklet_hi_schedule(&rdata->tasklet); + put_cpu(); +} + +#ifdef CONFIG_PREEMPT +/** + * call_rcu_preempt - Queue an RCU update request for preempt-safe reads + * @head: structure to be used for queueing the RCU updates. + * @func: actual update function to be invoked after the grace period + * @arg: argument to be passed to the update function + * + * The update function will be invoked as soon as all CPUs have performed a + * context switch or been seen in the idle loop or in a user process. + * It can be called only from process or BH context, however can be + * made to work from irq context too with minor code changes + * if necessary. The read-side of critical section doesn't require any + * protection, but updates may have long grace period in preemptive kernels. + * It should not be used for things like deferred kfree() unless such + * use can be guaranteed to be extremely infrequent. Doing otherwise + * can result in all your memory consumed while waiting for a + * low-priority preempted task to be rescheduled. + */ +void call_rcu_preempt(struct rcu_head *head, void (*func)(void *arg), void *arg) +{ + struct rcu_data *rdata = &rcu_data_preempt; + + head->func = func; + head->arg = arg; + rcu_preempt_lock(); + list_add(&head->list, &rdata->nxtlist); + rcu_preempt_unlock(); + tasklet_hi_schedule(&rdata->tasklet); +} +#endif + +/* + * Set up grace period detection for one batch of RCUs. + */ +static int rcu_prepare_polling(struct rcu_data *rdata) +{ + int stop; + int i; + + stop = 1; + if (!list_empty(&rdata->nxtlist)) { + list_splice(&rdata->nxtlist, &rdata->curlist); + INIT_LIST_HEAD(&rdata->nxtlist); + + rdata->polling = 1; + + for (i = 0; i < NR_CPUS; i++) { + if (!cpu_online(i)) + continue; + rdata->qsmask |= 1UL << i; + rdata->qcheckpt[i] = RCU_quiescent(i); + if (is_rcu_preempt_data(rdata)) + rcu_switch_preempt_cntr(i); + force_cpu_reschedule(i); + } + stop = 0; + } + + return stop; +} + +/* + * Invoke the completed RCU callbacks. + */ +static void rcu_invoke_callbacks(struct rcu_data *rdata) +{ + struct list_head *entry; + struct rcu_head *head; + + entry = rdata->curlist.prev; + do { + head = list_entry(entry, struct rcu_head, list); + entry = entry->prev; + head->func(head->arg); + } while (entry != &rdata->curlist); + INIT_LIST_HEAD(&rdata->curlist); +} + +static int rcu_completion(struct rcu_data *rdata) +{ + int stop; + + rdata->polling = 0; + rcu_invoke_callbacks(rdata); + stop = rcu_prepare_polling(rdata); + return stop; +} + +/* + * Poll for completion of grace period for this batch. + */ +static int rcu_polling(struct rcu_data *rdata) +{ + int i; + int stop; + + for (i = 0; i < NR_CPUS; i++) { + if (!cpu_online(i) || + !(rdata->qsmask & (1UL << i))) + continue; + + if ((rdata->qcheckpt[i] != RCU_quiescent(i)) && + (!is_rcu_preempt_data(rdata) || !is_rcu_cpu_preempted(i))) + rdata->qsmask &= ~(1UL << i); + else + break; + } + stop = 0; + if (!rdata->qsmask) + stop = rcu_completion(rdata); + return stop; +} + +/* + * Look into the per-cpu callback information to see if there is + * any processing necessary - if so do it. + */ +static void rcu_process_callbacks(unsigned long data) +{ + int stop; + struct rcu_data *rdata = (struct rcu_data *)data; + + if (is_rcu_preempt_data(rdata)) + rcu_preempt_lock(); + if (!rdata->polling) + stop = rcu_prepare_polling(rdata); + else + stop = rcu_polling(rdata); + if (is_rcu_preempt_data(rdata)) + rcu_preempt_unlock(); + + if (!stop) + tasklet_hi_schedule(&rdata->tasklet); +} + +/* Because of FASTCALL declaration of complete, we use this wrapper */ +static void wakeme_after_rcu(void *completion) +{ + complete(completion); +} + +static void rcu_data_init(struct rcu_data *rdata) +{ + tasklet_init(&rdata->tasklet, rcu_process_callbacks, + (unsigned long)rdata); + INIT_LIST_HEAD(&rdata->nxtlist); + INIT_LIST_HEAD(&rdata->curlist); +} + +/* + * Initializes rcu mechanism. Assumed to be called early. + * That is before local timer(SMP) or jiffie timer (uniproc) is setup. + */ +void __init rcu_init(void) +{ + int i; + + for (i = 0; i < NR_CPUS; i++) { + rcu_data_init(&rcu_data[i]); + } + rcu_data_preempt_init(); +} + +/** + * synchronize-kernel - wait until all the CPUs have gone + * through a "quiescent" state. It may sleep. + */ +void synchronize_kernel(void) +{ + struct rcu_head rcu; + DECLARE_COMPLETION(completion); + + /* Will wake me after RCU finished */ + call_rcu_preempt(&rcu, wakeme_after_rcu, &completion); + + /* Wait for it */ + wait_for_completion(&completion); +} + +EXPORT_SYMBOL(call_rcu); +EXPORT_SYMBOL(synchronize_kernel); +#ifdef CONFIG_PREEMPT +EXPORT_SYMBOL(call_rcu_preempt); +#endif diff -urN linux-2.5.34-base/kernel/sched.c linux-2.5.34-rcu_poll/kernel/sched.c --- linux-2.5.34-base/kernel/sched.c Mon Sep 9 23:05:05 2002 +++ linux-2.5.34-rcu_poll/kernel/sched.c Wed Sep 11 11:45:03 2002 @@ -25,6 +25,7 @@ #include <asm/mmu_context.h> #include <linux/interrupt.h> #include <linux/completion.h> +#include <linux/percpu.h> #include <linux/kernel_stat.h> #include <linux/security.h> #include <linux/notifier.h> @@ -158,12 +159,33 @@ static struct runqueue runqueues[NR_CPUS] __cacheline_aligned; +/* Fake initialization to work around compiler breakage */ +DEFINE_PER_CPU(long, cpu_quiescent) = 0L; + #define cpu_rq(cpu) (runqueues + (cpu)) #define this_rq() cpu_rq(smp_processor_id()) #define task_rq(p) cpu_rq(task_cpu(p)) #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #define rt_task(p) ((p)->prio < MAX_RT_PRIO) +#ifdef CONFIG_PREEMPT +/* Fake initialization to work around compiler breakage */ +DEFINE_PER_CPU(atomic_t[2], rcu_preempt_cntr) = + {ATOMIC_INIT(0), ATOMIC_INIT(0)}; +DEFINE_PER_CPU(atomic_t, *curr_preempt_cntr) = NULL; +DEFINE_PER_CPU(atomic_t, *next_preempt_cntr) = NULL; +static inline void rcu_init_preempt_cntr(int cpu) +{ + + atomic_set(&(per_cpu(rcu_preempt_cntr, cpu)[0]), 0); + atomic_set(&(per_cpu(rcu_preempt_cntr, cpu)[1]), 0); + per_cpu(curr_preempt_cntr, cpu) = + &(per_cpu(rcu_preempt_cntr, cpu)[1]); + per_cpu(next_preempt_cntr, cpu) = + &(per_cpu(rcu_preempt_cntr, cpu)[0]); +} +#endif + /* * Default context-switch locking: */ @@ -858,6 +880,10 @@ runqueue_t *rq = this_rq(); task_t *p = current; + if (user_ticks || + (idle_cpu(cpu) && !in_softirq() && hardirq_count() <= 1)) + per_cpu(cpu_quiescent, cpu)++; + if (p == rq->idle) { /* note: this timer irq context must be accounted for as well */ if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET) @@ -961,6 +987,8 @@ */ if (unlikely(preempt_count() & PREEMPT_ACTIVE)) goto pick_next_task; + else + rcu_preempt_put(); switch (prev->state) { case TASK_INTERRUPTIBLE: @@ -1003,6 +1031,7 @@ switch_tasks: prefetch(next); clear_tsk_need_resched(prev); + per_cpu(cpu_quiescent, prev->thread_info->cpu)++; if (likely(prev != next)) { rq->nr_switches++; @@ -1041,6 +1070,7 @@ need_resched: ti->preempt_count = PREEMPT_ACTIVE; + rcu_preempt_get(); schedule(); ti->preempt_count = 0; @@ -1269,6 +1299,18 @@ task_rq_unlock(rq, &flags); } +void force_cpu_reschedule(int cpu) +{ + struct runqueue *rq; + + rq = cpu_rq(cpu); + /* Need to save flags if someday called from irq context */ + spin_lock_irq(&rq->lock); + resched_task(rq->curr); + spin_unlock_irq(&rq->lock); +} + + #ifndef __alpha__ /* @@ -2108,6 +2150,7 @@ rq->expired = rq->arrays + 1; spin_lock_init(&rq->lock); INIT_LIST_HEAD(&rq->migration_queue); + rcu_init_preempt_cntr(i); for (j = 0; j < 2; j++) { array = rq->arrays + j;
- 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/
This archive was generated by hypermail 2b29 : Sun Sep 15 2002 - 22:00:25 EST