* 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 IBM Corporation, 2001
*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
#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/rcupdate.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
+#include <linux/module.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,
- .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock),
- .cpumask = CPU_MASK_NONE,
-};
-static struct rcu_ctrlblk rcu_bh_ctrlblk = {
- .cur = -300,
- .completed = -300,
- .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock),
- .cpumask = CPU_MASK_NONE,
+enum rcu_barrier {
+ RCU_BARRIER_STD,
+ RCU_BARRIER_BH,
+ RCU_BARRIER_SCHED,
};
-DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
-DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
-
-/* Fake initialization required by compiler */
-static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
-static int blimit = 10;
-static int qhimark = 10000;
-static int qlowmark = 100;
-
+static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
static struct completion rcu_barrier_completion;
-#ifdef CONFIG_SMP
-static void force_quiescent_state(struct rcu_data *rdp,
- struct rcu_ctrlblk *rcp)
-{
- int cpu;
- cpumask_t cpumask;
- set_need_resched();
- if (unlikely(!rcp->signaled)) {
- rcp->signaled = 1;
- /*
- * Don't send IPI to itself. With irqs disabled,
- * rdp->cpu is the current cpu.
- */
- cpumask = rcp->cpumask;
- cpu_clear(rdp->cpu, cpumask);
- for_each_cpu_mask(cpu, cpumask)
- smp_send_reschedule(cpu);
- }
-}
-#else
-static inline void force_quiescent_state(struct rcu_data *rdp,
- struct rcu_ctrlblk *rcp)
+/*
+ * Awaken the corresponding synchronize_rcu() instance now that a
+ * grace period has elapsed.
+ */
+void wakeme_after_rcu(struct rcu_head *head)
{
- set_need_resched();
+ struct rcu_synchronize *rcu;
+
+ rcu = container_of(head, struct rcu_synchronize, head);
+ complete(&rcu->completion);
}
-#endif
/**
- * 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
+ * synchronize_rcu - wait until a grace period has elapsed.
*
- * The update function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
+ * Control will return to the caller some time after a full grace
+ * period has elapsed, 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 fastcall call_rcu(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
-{
- unsigned long flags;
- struct rcu_data *rdp;
-
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_ctrlblk);
- }
- local_irq_restore(flags);
-}
-
-/**
- * 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 fastcall call_rcu_bh(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
-{
- unsigned long flags;
- struct rcu_data *rdp;
-
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_bh_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
-
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_bh_ctrlblk);
- }
-
- local_irq_restore(flags);
-}
-
-/*
- * Return the number of RCU batches processed thus far. Useful
- * for debug and statistics.
- */
-long rcu_batches_completed(void)
-{
- return rcu_ctrlblk.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;
-}
+synchronize_rcu_xxx(synchronize_rcu, call_rcu)
+EXPORT_SYMBOL_GPL(synchronize_rcu);
static void rcu_barrier_callback(struct rcu_head *notused)
{
/*
* Called with preemption disabled, and from cross-cpu IRQ context.
*/
-static void rcu_barrier_func(void *notused)
+static void rcu_barrier_func(void *type)
{
int cpu = smp_processor_id();
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- struct rcu_head *head;
+ struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
- head = &rdp->barrier;
atomic_inc(&rcu_barrier_cpu_count);
- call_rcu(head, rcu_barrier_callback);
+ switch ((enum rcu_barrier)type) {
+ case RCU_BARRIER_STD:
+ call_rcu(head, rcu_barrier_callback);
+ break;
+ case RCU_BARRIER_BH:
+ call_rcu_bh(head, rcu_barrier_callback);
+ break;
+ case RCU_BARRIER_SCHED:
+ call_rcu_sched(head, rcu_barrier_callback);
+ break;
+ }
}
-/**
- * rcu_barrier - Wait until all the in-flight RCUs are complete.
+/*
+ * Orchestrate the specified type of RCU barrier, waiting for all
+ * RCU callbacks of the specified type to complete.
*/
-void rcu_barrier(void)
+static void _rcu_barrier(enum rcu_barrier type)
{
BUG_ON(in_interrupt());
/* Take cpucontrol mutex to protect against CPU hotplug */
mutex_lock(&rcu_barrier_mutex);
init_completion(&rcu_barrier_completion);
atomic_set(&rcu_barrier_cpu_count, 0);
- on_each_cpu(rcu_barrier_func, NULL, 0, 1);
- wait_for_completion(&rcu_barrier_completion);
- mutex_unlock(&rcu_barrier_mutex);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-/*
- * Invoke the completed RCU callbacks. They are expected to be in
- * a per-cpu list.
- */
-static void rcu_do_batch(struct rcu_data *rdp)
-{
- 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_disable();
- rdp->qlen -= count;
- local_irq_enable();
- if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
- rdp->blimit = blimit;
-
- if (!rdp->donelist)
- rdp->donetail = &rdp->donelist;
- else
- tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
-}
-
-/*
- * 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->next_pending &&
- rcp->completed == rcp->cur) {
- rcp->next_pending = 0;
- /*
- * next_pending == 0 must be visible in
- * __rcu_process_callbacks() before it can see new value of cur.
- */
- smp_wmb();
- rcp->cur++;
-
- /*
- * 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();
- cpus_andnot(rcp->cpumask, cpu_online_map, 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)
-{
- 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(&rcp->lock);
/*
- * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
- * during cpu startup. Ignore the quiescent state.
+ * The queueing of callbacks in all CPUs must be atomic with
+ * respect to RCU, otherwise one CPU may queue a callback,
+ * wait for a grace period, decrement barrier count and call
+ * complete(), while other CPUs have not yet queued anything.
+ * So, we need to make sure that grace periods cannot complete
+ * until all the callbacks are queued.
*/
- if (likely(rdp->quiescbatch == rcp->cur))
- cpu_quiet(rdp->cpu, rcp);
-
- spin_unlock(&rcp->lock);
-}
-
-
-#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)
-{
- local_irq_disable();
- *this_rdp->nxttail = list;
- if (list)
- this_rdp->nxttail = tail;
- local_irq_enable();
-}
-
-static void __rcu_offline_cpu(struct rcu_data *this_rdp,
- struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
-{
- /* if the cpu going offline owns the grace period
- * we can block indefinitely waiting for it, so flush
- * it here
- */
- spin_lock_bh(&rcp->lock);
- if (rcp->cur != rcp->completed)
- cpu_quiet(rdp->cpu, rcp);
- spin_unlock_bh(&rcp->lock);
- rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
- rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
- rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
-}
-
-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);
- tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
-}
-
-#else
-
-static void rcu_offline_cpu(int cpu)
-{
+ rcu_read_lock();
+ on_each_cpu(rcu_barrier_func, (void *)type, 1);
+ rcu_read_unlock();
+ wait_for_completion(&rcu_barrier_completion);
+ mutex_unlock(&rcu_barrier_mutex);
}
-#endif
-
-/*
- * This does the RCU processing work from tasklet context.
+/**
+ * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
*/
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
- *rdp->donetail = rdp->curlist;
- rdp->donetail = rdp->curtail;
- rdp->curlist = NULL;
- rdp->curtail = &rdp->curlist;
- }
-
- if (rdp->nxtlist && !rdp->curlist) {
- local_irq_disable();
- rdp->curlist = rdp->nxtlist;
- rdp->curtail = rdp->nxttail;
- rdp->nxtlist = NULL;
- rdp->nxttail = &rdp->nxtlist;
- local_irq_enable();
-
- /*
- * start the next batch of callbacks
- */
-
- /* determine batch number */
- rdp->batch = rcp->cur + 1;
- /* see the comment and corresponding wmb() in
- * the rcu_start_batch()
- */
- smp_rmb();
-
- if (!rcp->next_pending) {
- /* and start it/schedule start if it's a new batch */
- spin_lock(&rcp->lock);
- rcp->next_pending = 1;
- rcu_start_batch(rcp);
- spin_unlock(&rcp->lock);
- }
- }
-
- rcu_check_quiescent_state(rcp, rdp);
- if (rdp->donelist)
- rcu_do_batch(rdp);
-}
-
-static void rcu_process_callbacks(unsigned long unused)
+void rcu_barrier(void)
{
- __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
- __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
-}
-
-static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
-{
- /* This cpu has pending rcu entries and the grace period
- * for them has completed.
- */
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
- return 1;
-
- /* This cpu has no pending entries, but there are new entries */
- if (!rdp->curlist && rdp->nxtlist)
- 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;
+ _rcu_barrier(RCU_BARRIER_STD);
}
+EXPORT_SYMBOL_GPL(rcu_barrier);
-/*
- * 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.
+/**
+ * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
*/
-int rcu_pending(int cpu)
+void rcu_barrier_bh(void)
{
- return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
- __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
+ _rcu_barrier(RCU_BARRIER_BH);
}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-/*
- * 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.
+/**
+ * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
*/
-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->curlist || !!rdp_bh->curlist || rcu_pending(cpu));
-}
-
-void rcu_check_callbacks(int cpu, int user)
-{
- if (user ||
- (idle_cpu(cpu) && !in_softirq() &&
- hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
- rcu_qsctr_inc(cpu);
- rcu_bh_qsctr_inc(cpu);
- } else if (!in_softirq())
- rcu_bh_qsctr_inc(cpu);
- tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
-}
-
-static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
+void rcu_barrier_sched(void)
{
- memset(rdp, 0, sizeof(*rdp));
- rdp->curtail = &rdp->curlist;
- rdp->nxttail = &rdp->nxtlist;
- rdp->donetail = &rdp->donelist;
- rdp->quiescbatch = rcp->completed;
- rdp->qs_pending = 0;
- rdp->cpu = cpu;
- rdp->blimit = blimit;
+ _rcu_barrier(RCU_BARRIER_SCHED);
}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-static void __devinit 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);
- tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
-}
-
-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)
{
- rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
- (void *)(long)smp_processor_id());
- /* Register notifier for non-boot CPUs */
- register_cpu_notifier(&rcu_nb);
-}
-
-struct rcu_synchronize {
- struct rcu_head head;
- struct completion completion;
-};
-
-/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(struct rcu_head *head)
-{
- struct rcu_synchronize *rcu;
-
- rcu = container_of(head, struct rcu_synchronize, head);
- complete(&rcu->completion);
+ __rcu_init();
}
-/**
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, 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.
- *
- * If your read-side code is not protected by rcu_read_lock(), do -not-
- * use synchronize_rcu().
- */
-void synchronize_rcu(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);
-}
-
-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
-EXPORT_SYMBOL_GPL(call_rcu);
-EXPORT_SYMBOL_GPL(call_rcu_bh);
-EXPORT_SYMBOL_GPL(synchronize_rcu);
git.samba.org / sfrench / cifs-2.6.git / blobdiff