#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;
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,
};
{
int cpu;
cpumask_t cpumask;
+ unsigned long flags;
+
set_need_resched();
+ spin_lock_irqsave(&rcp->lock, flags);
if (unlikely(!rcp->signaled)) {
rcp->signaled = 1;
/*
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,
}
#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);
+ }
+}
+
/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.
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);
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);
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();
}
/*
*/
static void rcu_do_batch(struct rcu_data *rdp)
{
+ unsigned long flags;
struct rcu_head *next, *list;
int count = 0;
}
rdp->donelist = list;
- local_irq_disable();
+ local_irq_save(flags);
rdp->qlen -= count;
- local_irq_enable();
+ local_irq_restore(flags);
if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
rdp->blimit = blimit;
* rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
* period (if necessary).
*/
+
+#ifdef CONFIG_DEBUG_RCU_STALL
+
+static inline void record_gp_check_time(struct rcu_ctrlblk *rcp)
+{
+ rcp->gp_check = get_seconds() + 3;
+}
+
+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 = get_seconds() - rcp->gp_check;
+ if (delta < 2L || cpus_empty(rcp->cpumask)) {
+ spin_unlock(&rcp->lock);
+ return;
+ }
+ rcp->gp_check = get_seconds() + 30;
+ spin_unlock_irqrestore(&rcp->lock, flags);
+
+ /* OK, time to rat on our buddy... */
+
+ printk(KERN_ERR "RCU detected CPU stalls:");
+ for_each_cpu_mask(cpu, rcp->cpumask)
+ printk(" %d", cpu);
+ printk(" (detected by %d, t=%lu/%lu)\n",
+ smp_processor_id(), get_seconds(), rcp->gp_check);
+}
+
+static void print_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+ unsigned long flags;
+
+ printk(KERN_ERR "RCU detected CPU %d stall (t=%lu/%lu)\n",
+ smp_processor_id(), get_seconds(), rcp->gp_check);
+ dump_stack();
+ spin_lock_irqsave(&rcp->lock, flags);
+ if ((long)(get_seconds() - rcp->gp_check) >= 0L)
+ rcp->gp_check = get_seconds() + 30;
+ spin_unlock_irqrestore(&rcp->lock, flags);
+}
+
+static void check_cpu_stall(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
+{
+ long delta;
+
+ delta = get_seconds() - rcp->gp_check;
+ if (cpu_isset(smp_processor_id(), rcp->cpumask) && delta >= 0L) {
+
+ /* We haven't checked in, so go dump stack. */
+
+ print_cpu_stall(rcp);
+
+ } else {
+ if (!cpus_empty(rcp->cpumask) && delta >= 2L) {
+ /* They had two seconds to dump stack, so complain. */
+ print_other_cpu_stall(rcp);
+ }
+ }
+}
+
+#else /* #ifdef CONFIG_DEBUG_RCU_STALL */
+
+static inline void record_gp_check_time(struct rcu_ctrlblk *rcp)
+{
+}
+
+static inline void
+check_cpu_stall(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_DEBUG_RCU_STALL */
+
/*
* 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.
*/
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++;
+ record_gp_check_time(rcp);
/*
* Accessing nohz_cpu_mask before incrementing rcp->cur needs a
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;
return;
rdp->qs_pending = 0;
- spin_lock(&rcp->lock);
+ 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(&rcp->lock);
+ spin_unlock_irqrestore(&rcp->lock, flags);
}
* 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();
+ 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)
{
- /* if the cpu going offline owns the grace period
+ 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_bh(&rcp->lock);
+ spin_lock_irqsave(&rcp->lock, flags);
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);
+ 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);
- local_irq_disable();
this_rdp->qlen += rdp->qlen;
- local_irq_enable();
+ local_irq_restore(flags);
}
static void rcu_offline_cpu(int cpu)
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;
- }
+ unsigned long flags;
+ long completed_snap;
- 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();
+ if (rdp->nxtlist) {
+ local_irq_save(flags);
+ completed_snap = ACCESS_ONCE(rcp->completed);
/*
- * start the next batch of callbacks
+ * 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];
- /* 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 (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 flags;
- 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);
+ spin_lock_irqsave(&rcp->lock, flags);
+ if (rcu_batch_after(rdp->batch, rcp->pending)) {
+ rcp->pending = rdp->batch;
+ rcu_start_batch(rcp);
+ }
+ spin_unlock_irqrestore(&rcp->lock, flags);
}
}
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)
{
- /* 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;
+ /* Check for CPU stalls, if enabled. */
+ check_cpu_stall(rcp, rdp);
- /* This cpu has no pending entries, but there are new entries */
- if (!rdp->curlist && rdp->nxtlist)
- return 1;
+ 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)
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);
}
+/*
+ * 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 ||
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->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;
rdp->cpu = cpu;
rdp->blimit = blimit;
+ spin_unlock_irqrestore(&rcp->lock, flags);
}
static void __cpuinit rcu_online_cpu(int cpu)
projects / linux-2.6-omap-h63xx.git / commitdiff