Merge branch 'linus' into core/rcu
diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h
index 8c77490..04c7281 100644
--- a/include/linux/rcuclassic.h
+++ b/include/linux/rcuclassic.h
@@ -45,7 +45,7 @@
struct rcu_ctrlblk {
long cur; /* Current batch number. */
long completed; /* Number of the last completed batch */
- int next_pending; /* Is the next batch already waiting? */
+ long pending; /* Number of the last pending batch */
int signaled;
@@ -66,11 +66,7 @@
return (a - b) > 0;
}
-/*
- * Per-CPU data for Read-Copy UPdate.
- * nxtlist - new callbacks are added here
- * curlist - current batch for which quiescent cycle started if any
- */
+/* Per-CPU data for Read-Copy UPdate. */
struct rcu_data {
/* 1) quiescent state handling : */
long quiescbatch; /* Batch # for grace period */
@@ -78,12 +74,24 @@
int qs_pending; /* core waits for quiesc state */
/* 2) batch handling */
- long batch; /* Batch # for current RCU batch */
+ /*
+ * if nxtlist is not NULL, then:
+ * batch:
+ * The batch # for the last entry of nxtlist
+ * [*nxttail[1], NULL = *nxttail[2]):
+ * Entries that batch # <= batch
+ * [*nxttail[0], *nxttail[1]):
+ * Entries that batch # <= batch - 1
+ * [nxtlist, *nxttail[0]):
+ * Entries that batch # <= batch - 2
+ * The grace period for these entries has completed, and
+ * the other grace-period-completed entries may be moved
+ * here temporarily in rcu_process_callbacks().
+ */
+ long batch;
struct rcu_head *nxtlist;
- struct rcu_head **nxttail;
+ struct rcu_head **nxttail[3];
long qlen; /* # of queued callbacks */
- struct rcu_head *curlist;
- struct rcu_head **curtail;
struct rcu_head *donelist;
struct rcu_head **donetail;
long blimit; /* Upper limit on a processed batch */
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index aad93cd..d427114 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -60,12 +60,14 @@
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,
};
@@ -118,6 +120,43 @@
}
#endif
+static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
+{
+ long batch;
+ smp_mb(); /* reads the most recently updated value of rcu->cur. */
+
+ /*
+ * 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);
+ }
+}
+
/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.
@@ -133,18 +172,11 @@
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);
- }
+ __call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data));
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(call_rcu);
@@ -169,20 +201,11 @@
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);
- }
-
+ __call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
@@ -211,12 +234,6 @@
static inline void raise_rcu_softirq(void)
{
raise_softirq(RCU_SOFTIRQ);
- /*
- * The smp_mb() here is required to ensure that this cpu's
- * __rcu_process_callbacks() reads the most recently updated
- * value of rcu->cur.
- */
- smp_mb();
}
/*
@@ -276,14 +293,8 @@
*/
static void rcu_start_batch(struct rcu_ctrlblk *rcp)
{
- if (rcp->next_pending &&
+ if (rcp->cur != rcp->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++;
/*
@@ -364,13 +375,15 @@
* 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)
+ struct rcu_head **tail, long batch)
{
- local_irq_disable();
- *this_rdp->nxttail = list;
- if (list)
- this_rdp->nxttail = tail;
- local_irq_enable();
+ if (list) {
+ local_irq_disable();
+ this_rdp->batch = batch;
+ *this_rdp->nxttail[2] = list;
+ this_rdp->nxttail[2] = tail;
+ local_irq_enable();
+ }
}
static void __rcu_offline_cpu(struct rcu_data *this_rdp,
@@ -384,9 +397,9 @@
if (rcp->cur != rcp->completed)
cpu_quiet(rdp->cpu, rcp);
spin_unlock_bh(&rcp->lock);
- rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
- rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
- rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
+ /* spin_lock implies smp_mb() */
+ 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);
local_irq_disable();
this_rdp->qlen += rdp->qlen;
@@ -420,37 +433,45 @@
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) {
+ if (rdp->nxtlist) {
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
+ * move the other grace-period-completed entries to
+ * [rdp->nxtlist, *rdp->nxttail[0]) temporarily
*/
+ if (!rcu_batch_before(rcp->completed, rdp->batch))
+ rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2];
+ else if (!rcu_batch_before(rcp->completed, rdp->batch - 1))
+ rdp->nxttail[0] = rdp->nxttail[1];
- /* determine batch number */
- rdp->batch = rcp->cur + 1;
- /* see the comment and corresponding wmb() in
- * the rcu_start_batch()
+ /*
+ * the grace period for entries in
+ * [rdp->nxtlist, *rdp->nxttail[0]) has completed and
+ * move these entries to donelist
*/
- smp_rmb();
+ if (rdp->nxttail[0] != &rdp->nxtlist) {
+ *rdp->donetail = rdp->nxtlist;
+ rdp->donetail = rdp->nxttail[0];
+ rdp->nxtlist = *rdp->nxttail[0];
+ *rdp->donetail = NULL;
- if (!rcp->next_pending) {
+ 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_enable();
+
+ if (rcu_batch_after(rdp->batch, rcp->pending)) {
/* and start it/schedule start if it's a new batch */
spin_lock(&rcp->lock);
- rcp->next_pending = 1;
- rcu_start_batch(rcp);
+ if (rcu_batch_after(rdp->batch, rcp->pending)) {
+ rcp->pending = rdp->batch;
+ rcu_start_batch(rcp);
+ }
spin_unlock(&rcp->lock);
}
}
@@ -468,15 +489,26 @@
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;
+ if (rdp->nxtlist) {
+ /*
+ * This cpu has pending rcu entries and the grace period
+ * for them has completed.
+ */
+ if (!rcu_batch_before(rcp->completed, rdp->batch))
+ return 1;
+ if (!rcu_batch_before(rcp->completed, rdp->batch - 1) &&
+ rdp->nxttail[0] != rdp->nxttail[1])
+ return 1;
+ if (rdp->nxttail[0] != &rdp->nxtlist)
+ return 1;
- /* This cpu has no pending entries, but there are new entries */
- if (!rdp->curlist && 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)
@@ -512,7 +544,7 @@
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));
+ return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu);
}
void rcu_check_callbacks(int cpu, int user)
@@ -559,8 +591,7 @@
struct rcu_data *rdp)
{
memset(rdp, 0, sizeof(*rdp));
- rdp->curtail = &rdp->curlist;
- rdp->nxttail = &rdp->nxtlist;
+ rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist;
rdp->donetail = &rdp->donelist;
rdp->quiescbatch = rcp->completed;
rdp->qs_pending = 0;
