/* Definition for rcupdate control block. */
struct rcu_ctrlblk rcu_ctrlblk =
- { .mutex = SPIN_LOCK_UNLOCKED, .curbatch = 1,
- .maxbatch = 1, .rcu_cpu_mask = CPU_MASK_NONE };
+ { .cur = -300, .completed = -300 , .lock = SEQCNT_ZERO };
+
+/* Bookkeeping of the progress of the grace period */
+struct {
+ spinlock_t mutex; /* Guard this struct and writes to rcu_ctrlblk */
+ cpumask_t rcu_cpu_mask; /* CPUs that need to switch in order */
+ /* for current batch to proceed. */
+} rcu_state ____cacheline_maxaligned_in_smp =
+ {.mutex = SPIN_LOCK_UNLOCKED, .rcu_cpu_mask = CPU_MASK_NONE };
+
+
DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
/* Fake initialization required by compiler */
* 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.
* The read-side of critical section that use call_rcu() for updation must
* be protected by rcu_read_lock()/rcu_read_unlock().
*/
-void fastcall call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg)
+void fastcall call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
{
int cpu;
unsigned long flags;
head->func = func;
- head->arg = arg;
+ head->next = NULL;
local_irq_save(flags);
cpu = smp_processor_id();
- list_add_tail(&head->list, &RCU_nxtlist(cpu));
+ *RCU_nxttail(cpu) = head;
+ RCU_nxttail(cpu) = &head->next;
local_irq_restore(flags);
}
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
-static void rcu_do_batch(struct list_head *list)
+static void rcu_do_batch(struct rcu_head *list)
{
- struct list_head *entry;
- struct rcu_head *head;
-
- while (!list_empty(list)) {
- entry = list->next;
- list_del(entry);
- head = list_entry(entry, struct rcu_head, list);
- head->func(head->arg);
+ struct rcu_head *next;
+
+ while (list) {
+ next = list->next;
+ list->func(list);
+ list = next;
}
}
+/*
+ * 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 rcu_ctrlblk.cur with
+ * RCU_quiescbatch(cpu). All cpus are recorded in the
+ * rcu_state.rcu_cpu_mask 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_state.rcu_cpu_mask. 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 the rcu_ctrlblk lock.
+ * Caller must hold rcu_state.mutex.
*/
-static void rcu_start_batch(long newbatch)
+static void rcu_start_batch(int next_pending)
{
- cpumask_t active;
-
- if (rcu_batch_before(rcu_ctrlblk.maxbatch, newbatch)) {
- rcu_ctrlblk.maxbatch = newbatch;
+ if (next_pending)
+ rcu_ctrlblk.next_pending = 1;
+
+ if (rcu_ctrlblk.next_pending &&
+ rcu_ctrlblk.completed == rcu_ctrlblk.cur) {
+ /* Can't change, since spin lock held. */
+ cpus_andnot(rcu_state.rcu_cpu_mask, cpu_online_map,
+ nohz_cpu_mask);
+ write_seqcount_begin(&rcu_ctrlblk.lock);
+ rcu_ctrlblk.next_pending = 0;
+ rcu_ctrlblk.cur++;
+ write_seqcount_end(&rcu_ctrlblk.lock);
}
- if (rcu_batch_before(rcu_ctrlblk.maxbatch, rcu_ctrlblk.curbatch) ||
- !cpus_empty(rcu_ctrlblk.rcu_cpu_mask)) {
- return;
+}
+
+/*
+ * 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)
+{
+ cpu_clear(cpu, rcu_state.rcu_cpu_mask);
+ if (cpus_empty(rcu_state.rcu_cpu_mask)) {
+ /* batch completed ! */
+ rcu_ctrlblk.completed = rcu_ctrlblk.cur;
+ rcu_start_batch(0);
}
- /* Can't change, since spin lock held. */
- active = nohz_cpu_mask;
- cpus_complement(active);
- cpus_and(rcu_ctrlblk.rcu_cpu_mask, cpu_online_map, active);
}
/*
{
int cpu = smp_processor_id();
- if (!cpu_isset(cpu, rcu_ctrlblk.rcu_cpu_mask))
+ if (RCU_quiescbatch(cpu) != rcu_ctrlblk.cur) {
+ /* new grace period: record qsctr value. */
+ RCU_qs_pending(cpu) = 1;
+ RCU_last_qsctr(cpu) = RCU_qsctr(cpu);
+ RCU_quiescbatch(cpu) = rcu_ctrlblk.cur;
+ return;
+ }
+
+ /* Grace period already completed for this cpu?
+ * qs_pending is checked instead of the actual bitmap to avoid
+ * cacheline trashing.
+ */
+ if (!RCU_qs_pending(cpu))
return;
/*
* we may miss one quiescent state of that CPU. That is
* tolerable. So no need to disable interrupts.
*/
- if (RCU_last_qsctr(cpu) == RCU_QSCTR_INVALID) {
- RCU_last_qsctr(cpu) = RCU_qsctr(cpu);
- return;
- }
if (RCU_qsctr(cpu) == RCU_last_qsctr(cpu))
return;
+ RCU_qs_pending(cpu) = 0;
- spin_lock(&rcu_ctrlblk.mutex);
- if (!cpu_isset(cpu, rcu_ctrlblk.rcu_cpu_mask))
- goto out_unlock;
-
- cpu_clear(cpu, rcu_ctrlblk.rcu_cpu_mask);
- RCU_last_qsctr(cpu) = RCU_QSCTR_INVALID;
- if (!cpus_empty(rcu_ctrlblk.rcu_cpu_mask))
- goto out_unlock;
-
- rcu_ctrlblk.curbatch++;
- rcu_start_batch(rcu_ctrlblk.maxbatch);
+ spin_lock(&rcu_state.mutex);
+ /*
+ * RCU_quiescbatch/batch.cur and the cpu bitmap can come out of sync
+ * during cpu startup. Ignore the quiescent state.
+ */
+ if (likely(RCU_quiescbatch(cpu) == rcu_ctrlblk.cur))
+ cpu_quiet(cpu);
-out_unlock:
- spin_unlock(&rcu_ctrlblk.mutex);
+ spin_unlock(&rcu_state.mutex);
}
* 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 list_head *list)
+static void rcu_move_batch(struct rcu_head *list)
{
- struct list_head *entry;
- int cpu = smp_processor_id();
+ int cpu;
local_irq_disable();
- while (!list_empty(list)) {
- entry = list->next;
- list_del(entry);
- list_add_tail(entry, &RCU_nxtlist(cpu));
+
+ cpu = smp_processor_id();
+
+ while (list != NULL) {
+ *RCU_nxttail(cpu) = list;
+ RCU_nxttail(cpu) = &list->next;
+ list = list->next;
}
local_irq_enable();
}
* we can block indefinitely waiting for it, so flush
* it here
*/
- spin_lock_irq(&rcu_ctrlblk.mutex);
- if (cpus_empty(rcu_ctrlblk.rcu_cpu_mask))
- goto unlock;
-
- cpu_clear(cpu, rcu_ctrlblk.rcu_cpu_mask);
- if (cpus_empty(rcu_ctrlblk.rcu_cpu_mask)) {
- rcu_ctrlblk.curbatch++;
- /* We may avoid calling start batch if
- * we are starting the batch only
- * because of the DEAD CPU (the current
- * CPU will start a new batch anyway for
- * the callbacks we will move to current CPU).
- * However, we will avoid this optimisation
- * for now.
- */
- rcu_start_batch(rcu_ctrlblk.maxbatch);
- }
-unlock:
- spin_unlock_irq(&rcu_ctrlblk.mutex);
+ spin_lock_bh(&rcu_state.mutex);
+ if (rcu_ctrlblk.cur != rcu_ctrlblk.completed)
+ cpu_quiet(cpu);
+ spin_unlock_bh(&rcu_state.mutex);
- rcu_move_batch(&RCU_curlist(cpu));
- rcu_move_batch(&RCU_nxtlist(cpu));
+ rcu_move_batch(RCU_curlist(cpu));
+ rcu_move_batch(RCU_nxtlist(cpu));
tasklet_kill_immediate(&RCU_tasklet(cpu), cpu);
}
#endif
+void rcu_restart_cpu(int cpu)
+{
+ spin_lock_bh(&rcu_state.mutex);
+ RCU_quiescbatch(cpu) = rcu_ctrlblk.completed;
+ RCU_qs_pending(cpu) = 0;
+ spin_unlock_bh(&rcu_state.mutex);
+}
+
/*
* This does the RCU processing work from tasklet context.
*/
static void rcu_process_callbacks(unsigned long unused)
{
int cpu = smp_processor_id();
- LIST_HEAD(list);
+ struct rcu_head *rcu_list = NULL;
- if (!list_empty(&RCU_curlist(cpu)) &&
- rcu_batch_after(rcu_ctrlblk.curbatch, RCU_batch(cpu))) {
- __list_splice(&RCU_curlist(cpu), &list);
- INIT_LIST_HEAD(&RCU_curlist(cpu));
+ if (RCU_curlist(cpu) &&
+ !rcu_batch_before(rcu_ctrlblk.completed, RCU_batch(cpu))) {
+ rcu_list = RCU_curlist(cpu);
+ RCU_curlist(cpu) = NULL;
}
local_irq_disable();
- if (!list_empty(&RCU_nxtlist(cpu)) && list_empty(&RCU_curlist(cpu))) {
- __list_splice(&RCU_nxtlist(cpu), &RCU_curlist(cpu));
- INIT_LIST_HEAD(&RCU_nxtlist(cpu));
+ if (RCU_nxtlist(cpu) && !RCU_curlist(cpu)) {
+ int next_pending, seq;
+
+ RCU_curlist(cpu) = RCU_nxtlist(cpu);
+ RCU_nxtlist(cpu) = NULL;
+ RCU_nxttail(cpu) = &RCU_nxtlist(cpu);
local_irq_enable();
/*
* start the next batch of callbacks
*/
- spin_lock(&rcu_ctrlblk.mutex);
- RCU_batch(cpu) = rcu_ctrlblk.curbatch + 1;
- rcu_start_batch(RCU_batch(cpu));
- spin_unlock(&rcu_ctrlblk.mutex);
+ do {
+ seq = read_seqcount_begin(&rcu_ctrlblk.lock);
+ /* determine batch number */
+ RCU_batch(cpu) = rcu_ctrlblk.cur + 1;
+ next_pending = rcu_ctrlblk.next_pending;
+ } while (read_seqcount_retry(&rcu_ctrlblk.lock, seq));
+
+ if (!next_pending) {
+ /* and start it/schedule start if it's a new batch */
+ spin_lock(&rcu_state.mutex);
+ rcu_start_batch(1);
+ spin_unlock(&rcu_state.mutex);
+ }
} else {
local_irq_enable();
}
rcu_check_quiescent_state();
- if (!list_empty(&list))
- rcu_do_batch(&list);
+ if (rcu_list)
+ rcu_do_batch(rcu_list);
}
void rcu_check_callbacks(int cpu, int user)
{
memset(&per_cpu(rcu_data, cpu), 0, sizeof(struct rcu_data));
tasklet_init(&RCU_tasklet(cpu), rcu_process_callbacks, 0UL);
- INIT_LIST_HEAD(&RCU_nxtlist(cpu));
- INIT_LIST_HEAD(&RCU_curlist(cpu));
+ RCU_nxttail(cpu) = &RCU_nxtlist(cpu);
+ RCU_quiescbatch(cpu) = rcu_ctrlblk.completed;
+ RCU_qs_pending(cpu) = 0;
}
static int __devinit rcu_cpu_notify(struct notifier_block *self,
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(void *completion)
+static void wakeme_after_rcu(struct rcu_head *head)
{
- complete(completion);
+ struct rcu_synchronize *rcu;
+
+ rcu = container_of(head, struct rcu_synchronize, head);
+ complete(&rcu->completion);
}
/**
*/
void synchronize_kernel(void)
{
- struct rcu_head rcu;
- DECLARE_COMPLETION(completion);
+ struct rcu_synchronize rcu;
+ init_completion(&rcu.completion);
/* Will wake me after RCU finished */
- call_rcu(&rcu, wakeme_after_rcu, &completion);
+ call_rcu(&rcu.head, wakeme_after_rcu);
/* Wait for it */
- wait_for_completion(&completion);
+ wait_for_completion(&rcu.completion);
}
git://git.onelab.eu / linux-2.6.git / blobdiff