/*
* 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 IBM Corporation, 2001
*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
*
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* 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 -
* Documentation/RCU
*
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/atomic.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/time.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map =
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
EXPORT_SYMBOL_GPL(rcu_lock_map);
#endif
/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_ctrlblk = {
.cur = -300,
.completed = -300,
.pending = -300,
.lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock),
.cpumask = CPU_MASK_NONE,
};
static struct rcu_ctrlblk rcu_bh_ctrlblk = {
.cur = -300,
.completed = -300,
.pending = -300,
.lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock),
.cpumask = CPU_MASK_NONE,
};
DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
static int blimit = 10;
static int qhimark = 10000;
static int qlowmark = 100;
#ifdef CONFIG_SMP
static void force_quiescent_state(struct rcu_data *rdp,
struct rcu_ctrlblk *rcp)
{
int cpu;
cpumask_t cpumask;
unsigned long flags;
set_need_resched();
spin_lock_irqsave(&rcp->lock, flags);
if (unlikely(!rcp->signaled)) {
rcp->signaled = 1;
/*
* Don't send IPI to itself. With irqs disabled,
* rdp->cpu is the current cpu.
*
* cpu_online_map is updated by the _cpu_down()
* using __stop_machine(). Since we're in irqs disabled
* section, __stop_machine() is not exectuting, hence
* the cpu_online_map is stable.
*
* However, a cpu might have been offlined _just_ before
* we disabled irqs while entering here.
* And rcu subsystem might not yet have handled the CPU_DEAD
* notification, leading to the offlined cpu's bit
* being set in the rcp->cpumask.
*
* Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
* sending smp_reschedule() to an offlined CPU.
*/
cpus_and(cpumask, rcp->cpumask, cpu_online_map);
cpu_clear(rdp->cpu, cpumask);
for_each_cpu_mask_nr(cpu, cpumask)
smp_send_reschedule(cpu);
}
spin_unlock_irqrestore(&rcp->lock, flags);
}
#else
static inline void force_quiescent_state(struct rcu_data *rdp,
struct rcu_ctrlblk *rcp)
{
set_need_resched();
}
#endif
static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp,
struct rcu_data *rdp)
{
long batch;
head->next = NULL;
smp_mb(); /* Read of rcu->cur must happen after any change by caller. */
/*
* Determine the batch number of this callback.
*
* Using ACCESS_ONCE to avoid the following error when gcc eliminates
* local variable "batch" and emits codes like this:
* 1) rdp->batch = rcp->cur + 1 # gets old value
* ......
* 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value
* then [*nxttail[0], *nxttail[1]) may contain callbacks
* that batch# = rdp->batch, see the comment of struct rcu_data.
*/
batch = ACCESS_ONCE(rcp->cur) + 1;
if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) {
/* process callbacks */
rdp->nxttail[0] = rdp->nxttail[1];
rdp->nxttail[1] = rdp->nxttail[2];
if (rcu_batch_after(batch - 1, rdp->batch))
rdp->nxttail[0] = rdp->nxttail[2];
}
rdp->batch = batch;
*rdp->nxttail[2] = head;
rdp->nxttail[2] = &head->next;
if (unlikely(++rdp->qlen > qhimark)) {
rdp->blimit = INT_MAX;
force_quiescent_state(rdp, &rcu_ctrlblk);
}
}
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
{
rcp->gp_start = jiffies;
rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
}
static void print_other_cpu_stall(struct rcu_ctrlblk *rcp)
{
int cpu;
long delta;
unsigned long flags;
/* Only let one CPU complain about others per time interval. */
spin_lock_irqsave(&rcp->lock, flags);
delta = jiffies - rcp->jiffies_stall;
if (delta < 2 || rcp->cur != rcp->completed) {
spin_unlock_irqrestore(&rcp->lock, flags);
return;
}
rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
spin_unlock_irqrestore(&rcp->lock, flags);
/* OK, time to rat on our buddy... */
printk(KERN_ERR "INFO: RCU detected CPU stalls:");
for_each_possible_cpu(cpu) {
if (cpu_isset(cpu, rcp->cpumask))
printk(" %d", cpu);
}
printk(" (detected by %d, t=%ld jiffies)\n",
smp_processor_id(), (long)(jiffies - rcp->gp_start));
}
static void print_cpu_stall(struct rcu_ctrlblk *rcp)
{
unsigned long flags;
printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu/%lu jiffies)\n",
smp_processor_id(), jiffies,
jiffies - rcp->gp_start);
dump_stack();
spin_lock_irqsave(&rcp->lock, flags);
if ((long)(jiffies - rcp->jiffies_stall) >= 0)
rcp->jiffies_stall =
jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
spin_unlock_irqrestore(&rcp->lock, flags);
set_need_resched(); /* kick ourselves to get things going. */
}
static void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
long delta;
delta = jiffies - rcp->jiffies_stall;
if (cpu_isset(smp_processor_id(), rcp->cpumask) && delta >= 0) {
/* We haven't checked in, so go dump stack. */
print_cpu_stall(rcp);
} else if (rcp->cur != rcp->completed && delta >= 2) {
/* They had two seconds to dump stack, so complain. */
print_other_cpu_stall(rcp);
}
}
#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp)
{
}
static inline void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
}
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.
* @func: actual update function to be invoked after the grace period
*
* The update function will be invoked some time after a full grace
* period elapses, 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.
*/
void call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu))
{
unsigned long flags;
head->func = func;
local_irq_save(flags);
__call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data));
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(call_rcu);
/**
* call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
* @head: structure to be used for queueing the RCU updates.
* @func: actual update function to be invoked after the grace period
*
* The update function will be invoked some time after a full grace
* period elapses, in other words after all currently executing RCU
* read-side critical sections have completed. call_rcu_bh() assumes
* that the read-side critical sections end on completion of a softirq
* handler. This means that read-side critical sections in process
* context must not be interrupted by softirqs. This interface is to be
* used when most of the read-side critical sections are in softirq context.
* RCU read-side critical sections are delimited by rcu_read_lock() and
* rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
* and rcu_read_unlock_bh(), if in process context. These may be nested.
*/
void call_rcu_bh(struct rcu_head *head,
void (*func)(struct rcu_head *rcu))
{
unsigned long flags;
head->func = func;
local_irq_save(flags);
__call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
/*
* Return the number of RCU batches processed thus far. Useful
* for debug and statistics.
*/
long rcu_batches_completed(void)
{
return rcu_ctrlblk.completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed);
/*
* Return the number of RCU batches processed thus far. Useful
* for debug and statistics.
*/
long rcu_batches_completed_bh(void)
{
return rcu_bh_ctrlblk.completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
/* Raises the softirq for processing rcu_callbacks. */
static inline void raise_rcu_softirq(void)
{
raise_softirq(RCU_SOFTIRQ);
}
/*
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
static void rcu_do_batch(struct rcu_data *rdp)
{
unsigned long flags;
struct rcu_head *next, *list;
int count = 0;
list = rdp->donelist;
while (list) {
next = list->next;
prefetch(next);
list->func(list);
list = next;
if (++count >= rdp->blimit)
break;
}
rdp->donelist = list;
local_irq_save(flags);
rdp->qlen -= count;
local_irq_restore(flags);
if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
rdp->blimit = blimit;
if (!rdp->donelist)
rdp->donetail = &rdp->donelist;
else
raise_rcu_softirq();
}
/*
* Grace period handling:
* The grace period handling consists out of two steps:
* - A new grace period is started.
* This is done by rcu_start_batch. The start is not broadcasted to
* all cpus, they must pick this up by comparing rcp->cur with
* rdp->quiescbatch. All cpus are recorded in the
* rcu_ctrlblk.cpumask bitmap.
* - All cpus must go through a quiescent state.
* Since the start of the grace period is not broadcasted, at least two
* calls to rcu_check_quiescent_state are required:
* The first call just notices that a new grace period is running. The
* following calls check if there was a quiescent state since the beginning
* of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
* the bitmap is empty, then the grace period is completed.
* rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
* period (if necessary).
*/
/*
* Register a new batch of callbacks, and start it up if there is currently no
* active batch and the batch to be registered has not already occurred.
* Caller must hold rcu_ctrlblk.lock.
*/
static void rcu_start_batch(struct rcu_ctrlblk *rcp)
{
if (rcp->cur != rcp->pending &&
rcp->completed == rcp->cur) {
rcp->cur++;
record_gp_stall_check_time(rcp);
/*
* Accessing nohz_cpu_mask before incrementing rcp->cur needs a
* Barrier Otherwise it can cause tickless idle CPUs to be
* included in rcp->cpumask, which will extend graceperiods
* unnecessarily.
*/
smp_mb();
cpumask_andnot(&rcp->cpumask, cpu_online_mask, nohz_cpu_mask);
rcp->signaled = 0;
}
}
/*
* cpu went through a quiescent state since the beginning of the grace period.
* Clear it from the cpu mask and complete the grace period if it was the last
* cpu. Start another grace period if someone has further entries pending
*/
static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
{
cpu_clear(cpu, rcp->cpumask);
if (cpus_empty(rcp->cpumask)) {
/* batch completed ! */
rcp->completed = rcp->cur;
rcu_start_batch(rcp);
}
}
/*
* Check if the cpu has gone through a quiescent state (say context
* switch). If so and if it already hasn't done so in this RCU
* quiescent cycle, then indicate that it has done so.
*/
static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
struct rcu_data *rdp)
{
unsigned long flags;
if (rdp->quiescbatch != rcp->cur) {
/* start new grace period: */
rdp->qs_pending = 1;
rdp->passed_quiesc = 0;
rdp->quiescbatch = rcp->cur;
return;
}
/* Grace period already completed for this cpu?
* qs_pending is checked instead of the actual bitmap to avoid
* cacheline trashing.
*/
if (!rdp->qs_pending)
return;
/*
* Was there a quiescent state since the beginning of the grace
* period? If no, then exit and wait for the next call.
*/
if (!rdp->passed_quiesc)
return;
rdp->qs_pending = 0;
spin_lock_irqsave(&rcp->lock, flags);
/*
* rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
* during cpu startup. Ignore the quiescent state.
*/
if (likely(rdp->quiescbatch == rcp->cur))
cpu_quiet(rdp->cpu, rcp);
spin_unlock_irqrestore(&rcp->lock, flags);
}
#ifdef CONFIG_HOTPLUG_CPU
/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
* locking requirements, the list it's pulling from has to belong to a cpu
* which is dead and hence not processing interrupts.
*/
static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
struct rcu_head **tail, long batch)
{
unsigned long flags;
if (list) {
local_irq_save(flags);
this_rdp->batch = batch;
*this_rdp->nxttail[2] = list;
this_rdp->nxttail[2] = tail;
local_irq_restore(flags);
}
}
static void __rcu_offline_cpu(struct rcu_data *this_rdp,
struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
{
unsigned long flags;
/*
* if the cpu going offline owns the grace period
* we can block indefinitely waiting for it, so flush
* it here
*/
spin_lock_irqsave(&rcp->lock, flags);
if (rcp->cur != rcp->completed)
cpu_quiet(rdp->cpu, rcp);
rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1);
rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1);
spin_unlock(&rcp->lock);
this_rdp->qlen += rdp->qlen;
local_irq_restore(flags);
}
static void rcu_offline_cpu(int cpu)
{
struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
__rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
&per_cpu(rcu_data, cpu));
__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
&per_cpu(rcu_bh_data, cpu));
put_cpu_var(rcu_data);
put_cpu_var(rcu_bh_data);
}
#else
static void rcu_offline_cpu(int cpu)
{
}
#endif
/*
* This does the RCU processing work from softirq context.
*/
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
struct rcu_data *rdp)
{
unsigned long flags;
long completed_snap;
if (rdp->nxtlist) {
local_irq_save(flags);
completed_snap = ACCESS_ONCE(rcp->completed);
/*
* move the other grace-period-completed entries to
* [rdp->nxtlist, *rdp->nxttail[0]) temporarily
*/
if (!rcu_batch_before(completed_snap, rdp->batch))
rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2];
else if (!rcu_batch_before(completed_snap, rdp->batch - 1))
rdp->nxttail[0] = rdp->nxttail[1];
/*
* the grace period for entries in
* [rdp->nxtlist, *rdp->nxttail[0]) has completed and
* move these entries to donelist
*/
if (rdp->nxttail[0] != &rdp->nxtlist) {
*rdp->donetail = rdp->nxtlist;
rdp->donetail = rdp->nxttail[0];
rdp->nxtlist = *rdp->nxttail[0];
*rdp->donetail = NULL;
if (rdp->nxttail[1] == rdp->nxttail[0])
rdp->nxttail[1] = &rdp->nxtlist;
if (rdp->nxttail[2] == rdp->nxttail[0])
rdp->nxttail[2] = &rdp->nxtlist;
rdp->nxttail[0] = &rdp->nxtlist;
}
local_irq_restore(flags);
if (rcu_batch_after(rdp->batch, rcp->pending)) {
unsigned long flags2;
/* and start it/schedule start if it's a new batch */
spin_lock_irqsave(&rcp->lock, flags2);
if (rcu_batch_after(rdp->batch, rcp->pending)) {
rcp->pending = rdp->batch;
rcu_start_batch(rcp);
}
spin_unlock_irqrestore(&rcp->lock, flags2);
}
}
rcu_check_quiescent_state(rcp, rdp);
if (rdp->donelist)
rcu_do_batch(rdp);
}
static void rcu_process_callbacks(struct softirq_action *unused)
{
/*
* Memory references from any prior RCU read-side critical sections
* executed by the interrupted code must be see before any RCU
* grace-period manupulations below.
*/
smp_mb(); /* See above block comment. */
__rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
__rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
/*
* Memory references from any later RCU read-side critical sections
* executed by the interrupted code must be see after any RCU
* grace-period manupulations above.
*/
smp_mb(); /* See above block comment. */
}
static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
{
/* Check for CPU stalls, if enabled. */
check_cpu_stall(rcp);
if (rdp->nxtlist) {
long completed_snap = ACCESS_ONCE(rcp->completed);
/*
* This cpu has pending rcu entries and the grace period
* for them has completed.
*/
if (!rcu_batch_before(completed_snap, rdp->batch))
return 1;
if (!rcu_batch_before(completed_snap, rdp->batch - 1) &&
rdp->nxttail[0] != rdp->nxttail[1])
return 1;
if (rdp->nxttail[0] != &rdp->nxtlist)
return 1;
/*
* This cpu has pending rcu entries and the new batch
* for then hasn't been started nor scheduled start
*/
if (rcu_batch_after(rdp->batch, rcp->pending))
return 1;
}
/* This cpu has finished callbacks to invoke */
if (rdp->donelist)
return 1;
/* The rcu core waits for a quiescent state from the cpu */
if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
return 1;
/* nothing to do */
return 0;
}
/*
* Check to see if there is any immediate RCU-related work to be done
* by the current CPU, returning 1 if so. This function is part of the
* RCU implementation; it is -not- an exported member of the RCU API.
*/
int rcu_pending(int cpu)
{
return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
__rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
}
/*
* Check to see if any future RCU-related work will need to be done
* by the current CPU, even if none need be done immediately, returning
* 1 if so. This function is part of the RCU implementation; it is -not-
* an exported member of the RCU API.
*/
int rcu_needs_cpu(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu);
return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu);
}
/*
* Top-level function driving RCU grace-period detection, normally
* invoked from the scheduler-clock interrupt. This function simply
* increments counters that are read only from softirq by this same
* CPU, so there are no memory barriers required.
*/
void rcu_check_callbacks(int cpu, int user)
{
if (user ||
(idle_cpu(cpu) && !in_softirq() &&
hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
/*
* Get here if this CPU took its interrupt from user
* mode or from the idle loop, and if this is not a
* nested interrupt. In this case, the CPU is in
* a quiescent state, so count it.
*
* Also do a memory barrier. This is needed to handle
* the case where writes from a preempt-disable section
* of code get reordered into schedule() by this CPU's
* write buffer. The memory barrier makes sure that
* the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see
* by other CPUs to happen after any such write.
*/
smp_mb(); /* See above block comment. */
rcu_qsctr_inc(cpu);
rcu_bh_qsctr_inc(cpu);
} else if (!in_softirq()) {
/*
* Get here if this CPU did not take its interrupt from
* softirq, in other words, if it is not interrupting
* a rcu_bh read-side critical section. This is an _bh
* critical section, so count it. The memory barrier
* is needed for the same reason as is the above one.
*/
smp_mb(); /* See above block comment. */
rcu_bh_qsctr_inc(cpu);
}
raise_rcu_softirq();
}
static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
struct rcu_data *rdp)
{
unsigned long flags;
spin_lock_irqsave(&rcp->lock, flags);
memset(rdp, 0, sizeof(*rdp));
rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist;
rdp->donetail = &rdp->donelist;
rdp->quiescbatch = rcp->completed;
rdp->qs_pending = 0;
rdp->cpu = cpu;
rdp->blimit = blimit;
spin_unlock_irqrestore(&rcp->lock, flags);
}
static void __cpuinit rcu_online_cpu(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
}
static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
rcu_online_cpu(cpu);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
rcu_offline_cpu(cpu);
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block __cpuinitdata rcu_nb = {
.notifier_call = rcu_cpu_notify,
};
/*
* Initializes rcu mechanism. Assumed to be called early.
* That is before local timer(SMP) or jiffie timer (uniproc) is setup.
* Note that rcu_qsctr and friends are implicitly
* initialized due to the choice of ``0'' for RCU_CTR_INVALID.
*/
void __init __rcu_init(void)
{
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
/* Register notifier for non-boot CPUs */
register_cpu_notifier(&rcu_nb);
}
module_param(blimit, int, 0);
module_param(qhimark, int, 0);
module_param(qlowmark, int, 0);
