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Subject[PATCH] Read-Copy Update 2.5.36
Hi,

Here is RCU for 2.5.36. It is just a rediff from earlier 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. The synchronize_kernel() interface uses call_rcu_preempt()
since it is not concerned about latencies. synchronize_kernel() is
equivalent of wait_for_later() in the "later" patch published
by Rusty earlier as a part of the new in-kernel module loader.
The module-loader needs only a part of rcu_poll funcationality.

Thanks
--
Dipankar Sarma <dipankar@in.ibm.com> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.


diff -urN linux-2.5.36-base/include/linux/init_task.h linux-2.5.36-rcu_poll/include/linux/init_task.h
--- linux-2.5.36-base/include/linux/init_task.h Wed Sep 18 06:28:45 2002
+++ linux-2.5.36-rcu_poll/include/linux/init_task.h Wed Sep 18 16:17:08 2002
@@ -98,6 +98,7 @@
.alloc_lock = SPIN_LOCK_UNLOCKED, \
.switch_lock = SPIN_LOCK_UNLOCKED, \
.journal_info = NULL, \
+ .cpu_preempt_cntr = NULL, \
}


diff -urN linux-2.5.36-base/include/linux/rcupdate.h linux-2.5.36-rcu_poll/include/linux/rcupdate.h
--- linux-2.5.36-base/include/linux/rcupdate.h Thu Jan 1 05:30:00 1970
+++ linux-2.5.36-rcu_poll/include/linux/rcupdate.h Wed Sep 18 16:17:08 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-2.5.36-base/include/linux/sched.h linux-2.5.36-rcu_poll/include/linux/sched.h
--- linux-2.5.36-base/include/linux/sched.h Wed Sep 18 06:28:45 2002
+++ linux-2.5.36-rcu_poll/include/linux/sched.h Wed Sep 18 16:17:48 2002
@@ -28,6 +28,7 @@
#include <linux/fs_struct.h>
#include <linux/compiler.h>
#include <linux/completion.h>
+#include <linux/percpu.h>

struct exec_domain;

@@ -167,6 +168,7 @@
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;

@@ -396,6 +398,7 @@
/* journalling filesystem info */
void *journal_info;
struct dentry *proc_dentry;
+ atomic_t *cpu_preempt_cntr;
};

extern void __put_task_struct(struct task_struct *tsk);
@@ -473,6 +476,8 @@
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
@@ -1024,6 +1029,55 @@

#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-2.5.36-base/init/main.c linux-2.5.36-rcu_poll/init/main.c
--- linux-2.5.36-base/init/main.c Wed Sep 18 06:28:47 2002
+++ linux-2.5.36-rcu_poll/init/main.c Wed Sep 18 16:17:08 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>
@@ -395,6 +396,7 @@
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-2.5.36-base/kernel/Makefile linux-2.5.36-rcu_poll/kernel/Makefile
--- linux-2.5.36-base/kernel/Makefile Wed Sep 18 06:28:48 2002
+++ linux-2.5.36-rcu_poll/kernel/Makefile Wed Sep 18 16:17:08 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-2.5.36-base/kernel/exit.c linux-2.5.36-rcu_poll/kernel/exit.c
--- linux-2.5.36-base/kernel/exit.c Wed Sep 18 06:28:50 2002
+++ linux-2.5.36-rcu_poll/kernel/exit.c Wed Sep 18 16:17:08 2002
@@ -637,6 +637,7 @@
preempt_disable();
if (current->exit_signal == -1)
release_task(current);
+ rcu_preempt_put();
schedule();
BUG();
/*
diff -urN linux-2.5.36-base/kernel/fork.c linux-2.5.36-rcu_poll/kernel/fork.c
--- linux-2.5.36-base/kernel/fork.c Wed Sep 18 06:28:45 2002
+++ linux-2.5.36-rcu_poll/kernel/fork.c Wed Sep 18 16:17:08 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-2.5.36-base/kernel/rcupdate.c linux-2.5.36-rcu_poll/kernel/rcupdate.c
--- linux-2.5.36-base/kernel/rcupdate.c Thu Jan 1 05:30:00 1970
+++ linux-2.5.36-rcu_poll/kernel/rcupdate.c Wed Sep 18 16:17:08 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-2.5.36-base/kernel/sched.c linux-2.5.36-rcu_poll/kernel/sched.c
--- linux-2.5.36-base/kernel/sched.c Wed Sep 18 06:28:48 2002
+++ linux-2.5.36-rcu_poll/kernel/sched.c Wed Sep 18 16:17:08 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;
-
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