#include <asm/atomic.h>
#include <linux/bitops.h>
#include <linux/module.h>
+ #include <linux/kthread.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/random.h>
#include <linux/delay.h>
spinlock_t lock; /* Protect rcu_data fields. */
long completed; /* Number of last completed batch. */
int waitlistcount;
- struct tasklet_struct rcu_tasklet;
struct rcu_head *nextlist;
struct rcu_head **nexttail;
struct rcu_head *waitlist[GP_STAGES];
struct rcu_head **waittail[GP_STAGES];
- struct rcu_head *donelist;
+ struct rcu_head *donelist; /* from waitlist & waitschedlist */
struct rcu_head **donetail;
long rcu_flipctr[2];
+ struct rcu_head *nextschedlist;
+ struct rcu_head **nextschedtail;
+ struct rcu_head *waitschedlist;
+ struct rcu_head **waitschedtail;
+ int rcu_sched_sleeping;
#ifdef CONFIG_RCU_TRACE
struct rcupreempt_trace trace;
#endif /* #ifdef CONFIG_RCU_TRACE */
rcu_try_flip_waitmb_state,
};
+ /*
+ * States for rcu_ctrlblk.rcu_sched_sleep.
+ */
+
+ enum rcu_sched_sleep_states {
+ rcu_sched_not_sleeping, /* Not sleeping, callbacks need GP. */
+ rcu_sched_sleep_prep, /* Thinking of sleeping, rechecking. */
+ rcu_sched_sleeping, /* Sleeping, awaken if GP needed. */
+ };
+
struct rcu_ctrlblk {
spinlock_t fliplock; /* Protect state-machine transitions. */
long completed; /* Number of last completed batch. */
enum rcu_try_flip_states rcu_try_flip_state; /* The current state of
the rcu state machine */
+ spinlock_t schedlock; /* Protect rcu_sched sleep state. */
+ enum rcu_sched_sleep_states sched_sleep; /* rcu_sched state. */
+ wait_queue_head_t sched_wq; /* Place for rcu_sched to sleep. */
};
static DEFINE_PER_CPU(struct rcu_data, rcu_data);
.fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock),
.completed = 0,
.rcu_try_flip_state = rcu_try_flip_idle_state,
+ .schedlock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.schedlock),
+ .sched_sleep = rcu_sched_not_sleeping,
+ .sched_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rcu_ctrlblk.sched_wq),
};
+ static struct task_struct *rcu_sched_grace_period_task;
#ifdef CONFIG_RCU_TRACE
static char *rcu_try_flip_state_names[] =
*/
#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
+ #define RCU_SCHED_BATCH_TIME (HZ / 50)
+
/*
* Return the number of RCU batches processed thus far. Useful
* for debug and statistics.
}
}
- #ifdef CONFIG_NO_HZ
+ DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched) = {
+ .dynticks = 1,
+ };
- DEFINE_PER_CPU(long, dynticks_progress_counter) = 1;
- static DEFINE_PER_CPU(long, rcu_dyntick_snapshot);
+ #ifdef CONFIG_NO_HZ
static DEFINE_PER_CPU(int, rcu_update_flag);
/**
* rcu_irq_enter - Called from Hard irq handlers and NMI/SMI.
*
* If the CPU was idle with dynamic ticks active, this updates the
- * dynticks_progress_counter to let the RCU handling know that the
+ * rcu_dyntick_sched.dynticks to let the RCU handling know that the
* CPU is active.
*/
void rcu_irq_enter(void)
{
int cpu = smp_processor_id();
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
if (per_cpu(rcu_update_flag, cpu))
per_cpu(rcu_update_flag, cpu)++;
/*
* Only update if we are coming from a stopped ticks mode
- * (dynticks_progress_counter is even).
+ * (rcu_dyntick_sched.dynticks is even).
*/
if (!in_interrupt() &&
- (per_cpu(dynticks_progress_counter, cpu) & 0x1) == 0) {
+ (rdssp->dynticks & 0x1) == 0) {
/*
* The following might seem like we could have a race
* with NMI/SMIs. But this really isn't a problem.
* RCU read-side critical sections on this CPU would
* have already completed.
*/
- per_cpu(dynticks_progress_counter, cpu)++;
+ rdssp->dynticks++;
/*
* The following memory barrier ensures that any
* rcu_read_lock() primitives in the irq handler
* are seen by other CPUs to follow the above
- * increment to dynticks_progress_counter. This is
+ * increment to rcu_dyntick_sched.dynticks. This is
* required in order for other CPUs to correctly
* determine when it is safe to advance the RCU
* grace-period state machine.
smp_mb(); /* see above block comment. */
/*
* Since we can't determine the dynamic tick mode from
- * the dynticks_progress_counter after this routine,
+ * the rcu_dyntick_sched.dynticks after this routine,
* we use a second flag to acknowledge that we came
* from an idle state with ticks stopped.
*/
/*
* If we take an NMI/SMI now, they will also increment
* the rcu_update_flag, and will not update the
- * dynticks_progress_counter on exit. That is for
+ * rcu_dyntick_sched.dynticks on exit. That is for
* this IRQ to do.
*/
}
* rcu_irq_exit - Called from exiting Hard irq context.
*
* If the CPU was idle with dynamic ticks active, update the
- * dynticks_progress_counter to put let the RCU handling be
+ * rcu_dyntick_sched.dynticks to put let the RCU handling be
* aware that the CPU is going back to idle with no ticks.
*/
void rcu_irq_exit(void)
{
int cpu = smp_processor_id();
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
/*
* rcu_update_flag is set if we interrupted the CPU
* Once this occurs, we keep track of interrupt nesting
* because a NMI/SMI could also come in, and we still
* only want the IRQ that started the increment of the
- * dynticks_progress_counter to be the one that modifies
+ * rcu_dyntick_sched.dynticks to be the one that modifies
* it on exit.
*/
if (per_cpu(rcu_update_flag, cpu)) {
/*
* If an NMI/SMI happens now we are still
- * protected by the dynticks_progress_counter being odd.
+ * protected by the rcu_dyntick_sched.dynticks being odd.
*/
/*
* The following memory barrier ensures that any
* rcu_read_unlock() primitives in the irq handler
* are seen by other CPUs to preceed the following
- * increment to dynticks_progress_counter. This
+ * increment to rcu_dyntick_sched.dynticks. This
* is required in order for other CPUs to determine
* when it is safe to advance the RCU grace-period
* state machine.
*/
smp_mb(); /* see above block comment. */
- per_cpu(dynticks_progress_counter, cpu)++;
- WARN_ON(per_cpu(dynticks_progress_counter, cpu) & 0x1);
+ rdssp->dynticks++;
+ WARN_ON(rdssp->dynticks & 0x1);
}
}
static void dyntick_save_progress_counter(int cpu)
{
- per_cpu(rcu_dyntick_snapshot, cpu) =
- per_cpu(dynticks_progress_counter, cpu);
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+ rdssp->dynticks_snap = rdssp->dynticks;
}
static inline int
{
long curr;
long snap;
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
- curr = per_cpu(dynticks_progress_counter, cpu);
- snap = per_cpu(rcu_dyntick_snapshot, cpu);
+ curr = rdssp->dynticks;
+ snap = rdssp->dynticks_snap;
smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
/*
* that this CPU already acknowledged the counter.
*/
- if ((curr - snap) > 2 || (snap & 0x1) == 0)
+ if ((curr - snap) > 2 || (curr & 0x1) == 0)
return 0;
/* We need this CPU to explicitly acknowledge the counter flip. */
{
long curr;
long snap;
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
- curr = per_cpu(dynticks_progress_counter, cpu);
- snap = per_cpu(rcu_dyntick_snapshot, cpu);
+ curr = rdssp->dynticks;
+ snap = rdssp->dynticks_snap;
smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
/*
return 1;
}
+ static void dyntick_save_progress_counter_sched(int cpu)
+ {
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+ rdssp->sched_dynticks_snap = rdssp->dynticks;
+ }
+
+ static int rcu_qsctr_inc_needed_dyntick(int cpu)
+ {
+ long curr;
+ long snap;
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+ curr = rdssp->dynticks;
+ snap = rdssp->sched_dynticks_snap;
+ smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
+
+ /*
+ * If the CPU remained in dynticks mode for the entire time
+ * and didn't take any interrupts, NMIs, SMIs, or whatever,
+ * then it cannot be in the middle of an rcu_read_lock(), so
+ * the next rcu_read_lock() it executes must use the new value
+ * of the counter. Therefore, this CPU has been in a quiescent
+ * state the entire time, and we don't need to wait for it.
+ */
+
+ if ((curr == snap) && ((curr & 0x1) == 0))
+ return 0;
+
+ /*
+ * If the CPU passed through or entered a dynticks idle phase with
+ * no active irq handlers, then, as above, this CPU has already
+ * passed through a quiescent state.
+ */
+
+ if ((curr - snap) > 2 || (snap & 0x1) == 0)
+ return 0;
+
+ /* We need this CPU to go through a quiescent state. */
+
+ return 1;
+ }
+
#else /* !CONFIG_NO_HZ */
- # define dyntick_save_progress_counter(cpu) do { } while (0)
- # define rcu_try_flip_waitack_needed(cpu) (1)
- # define rcu_try_flip_waitmb_needed(cpu) (1)
+ # define dyntick_save_progress_counter(cpu) do { } while (0)
+ # define rcu_try_flip_waitack_needed(cpu) (1)
+ # define rcu_try_flip_waitmb_needed(cpu) (1)
+
+ # define dyntick_save_progress_counter_sched(cpu) do { } while (0)
+ # define rcu_qsctr_inc_needed_dyntick(cpu) (1)
#endif /* CONFIG_NO_HZ */
+ static void save_qsctr_sched(int cpu)
+ {
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+ rdssp->sched_qs_snap = rdssp->sched_qs;
+ }
+
+ static inline int rcu_qsctr_inc_needed(int cpu)
+ {
+ struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+ /*
+ * If there has been a quiescent state, no more need to wait
+ * on this CPU.
+ */
+
+ if (rdssp->sched_qs != rdssp->sched_qs_snap) {
+ smp_mb(); /* force ordering with cpu entering schedule(). */
+ return 0;
+ }
+
+ /* We need this CPU to go through a quiescent state. */
+
+ return 1;
+ }
+
/*
* Get here when RCU is idle. Decide whether we need to
* move out of idle state, and return non-zero if so.
unsigned long flags;
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+ /*
+ * If this CPU took its interrupt from user mode or from the
+ * idle loop, and this is not a nested interrupt, then
+ * this CPU has to have exited all prior preept-disable
+ * sections of code. So increment the counter to note this.
+ *
+ * The memory barrier 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. So the memory
+ * barrier makes sure that the rcu_qsctr_inc() is seen by other
+ * CPUs to happen after any such write.
+ */
+
+ if (user ||
+ (idle_cpu(cpu) && !in_softirq() &&
+ hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+ smp_mb(); /* Guard against aggressive schedule(). */
+ rcu_qsctr_inc(cpu);
+ }
+
rcu_check_mb(cpu);
if (rcu_ctrlblk.completed == rdp->completed)
rcu_try_flip();
struct rcu_head *list = NULL;
unsigned long flags;
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+ struct rcu_head *schedlist = NULL;
+ struct rcu_head **schedtail = &schedlist;
struct rcu_head **tail = &list;
/*
rcu_offline_cpu_enqueue(rdp->waitlist[i], rdp->waittail[i],
list, tail);
rcu_offline_cpu_enqueue(rdp->nextlist, rdp->nexttail, list, tail);
+ rcu_offline_cpu_enqueue(rdp->waitschedlist, rdp->waitschedtail,
+ schedlist, schedtail);
+ rcu_offline_cpu_enqueue(rdp->nextschedlist, rdp->nextschedtail,
+ schedlist, schedtail);
+ rdp->rcu_sched_sleeping = 0;
spin_unlock_irqrestore(&rdp->lock, flags);
rdp->waitlistcount = 0;
* fix.
*/
- local_irq_save(flags);
+ local_irq_save(flags); /* disable preempt till we know what lock. */
rdp = RCU_DATA_ME();
spin_lock(&rdp->lock);
*rdp->nexttail = list;
if (list)
rdp->nexttail = tail;
+ *rdp->nextschedtail = schedlist;
+ if (schedlist)
+ rdp->nextschedtail = schedtail;
spin_unlock_irqrestore(&rdp->lock, flags);
}
void __cpuinit rcu_online_cpu(int cpu)
{
unsigned long flags;
+ struct rcu_data *rdp;
spin_lock_irqsave(&rcu_ctrlblk.fliplock, flags);
cpu_set(cpu, rcu_cpu_online_map);
spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags);
+
+ /*
+ * The rcu_sched grace-period processing might have bypassed
+ * this CPU, given that it was not in the rcu_cpu_online_map
+ * when the grace-period scan started. This means that the
+ * grace-period task might sleep. So make sure that if this
+ * should happen, the first callback posted to this CPU will
+ * wake up the grace-period task if need be.
+ */
+
+ rdp = RCU_DATA_CPU(cpu);
+ spin_lock_irqsave(&rdp->lock, flags);
+ rdp->rcu_sched_sleeping = 1;
+ spin_unlock_irqrestore(&rdp->lock, flags);
}
static void rcu_process_callbacks(struct softirq_action *unused)
*rdp->nexttail = head;
rdp->nexttail = &head->next;
RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
- spin_unlock(&rdp->lock);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&rdp->lock, flags);
}
EXPORT_SYMBOL_GPL(call_rcu);
+ void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+ {
+ unsigned long flags;
+ struct rcu_data *rdp;
+ int wake_gp = 0;
+
+ head->func = func;
+ head->next = NULL;
+ local_irq_save(flags);
+ rdp = RCU_DATA_ME();
+ spin_lock(&rdp->lock);
+ *rdp->nextschedtail = head;
+ rdp->nextschedtail = &head->next;
+ if (rdp->rcu_sched_sleeping) {
+
+ /* Grace-period processing might be sleeping... */
+
+ rdp->rcu_sched_sleeping = 0;
+ wake_gp = 1;
+ }
+ spin_unlock_irqrestore(&rdp->lock, flags);
+ if (wake_gp) {
+
+ /* Wake up grace-period processing, unless someone beat us. */
+
+ spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+ if (rcu_ctrlblk.sched_sleep != rcu_sched_sleeping)
+ wake_gp = 0;
+ rcu_ctrlblk.sched_sleep = rcu_sched_not_sleeping;
+ spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+ if (wake_gp)
+ wake_up_interruptible(&rcu_ctrlblk.sched_wq);
+ }
+ }
+ EXPORT_SYMBOL_GPL(call_rcu_sched);
+
/*
* Wait until all currently running preempt_disable() code segments
* (including hardware-irq-disable segments) complete. Note that
* in -rt this does -not- necessarily result in all currently executing
* interrupt -handlers- having completed.
*/
- void __synchronize_sched(void)
+ synchronize_rcu_xxx(__synchronize_sched, call_rcu_sched)
+ EXPORT_SYMBOL_GPL(__synchronize_sched);
+
+ /*
+ * kthread function that manages call_rcu_sched grace periods.
+ */
+ static int rcu_sched_grace_period(void *arg)
{
- cpumask_t oldmask;
+ int couldsleep; /* might sleep after current pass. */
+ int couldsleepnext = 0; /* might sleep after next pass. */
int cpu;
+ unsigned long flags;
+ struct rcu_data *rdp;
+ int ret;
- if (sched_getaffinity(0, &oldmask) < 0)
- oldmask = cpu_possible_map;
- for_each_online_cpu(cpu) {
- sched_setaffinity(0, &cpumask_of_cpu(cpu));
- schedule();
- }
- sched_setaffinity(0, &oldmask);
+ /*
+ * Each pass through the following loop handles one
+ * rcu_sched grace period cycle.
+ */
+ do {
+ /* Save each CPU's current state. */
+
+ for_each_online_cpu(cpu) {
+ dyntick_save_progress_counter_sched(cpu);
+ save_qsctr_sched(cpu);
+ }
+
+ /*
+ * Sleep for about an RCU grace-period's worth to
+ * allow better batching and to consume less CPU.
+ */
+ schedule_timeout_interruptible(RCU_SCHED_BATCH_TIME);
+
+ /*
+ * If there was nothing to do last time, prepare to
+ * sleep at the end of the current grace period cycle.
+ */
+ couldsleep = couldsleepnext;
+ couldsleepnext = 1;
+ if (couldsleep) {
+ spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+ rcu_ctrlblk.sched_sleep = rcu_sched_sleep_prep;
+ spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+ }
+
+ /*
+ * Wait on each CPU in turn to have either visited
+ * a quiescent state or been in dynticks-idle mode.
+ */
+ for_each_online_cpu(cpu) {
+ while (rcu_qsctr_inc_needed(cpu) &&
+ rcu_qsctr_inc_needed_dyntick(cpu)) {
+ /* resched_cpu(cpu); @@@ */
+ schedule_timeout_interruptible(1);
+ }
+ }
+
+ /* Advance callbacks for each CPU. */
+
+ for_each_online_cpu(cpu) {
+
+ rdp = RCU_DATA_CPU(cpu);
+ spin_lock_irqsave(&rdp->lock, flags);
+
+ /*
+ * We are running on this CPU irq-disabled, so no
+ * CPU can go offline until we re-enable irqs.
+ * The current CPU might have already gone
+ * offline (between the for_each_offline_cpu and
+ * the spin_lock_irqsave), but in that case all its
+ * callback lists will be empty, so no harm done.
+ *
+ * Advance the callbacks! We share normal RCU's
+ * donelist, since callbacks are invoked the
+ * same way in either case.
+ */
+ if (rdp->waitschedlist != NULL) {
+ *rdp->donetail = rdp->waitschedlist;
+ rdp->donetail = rdp->waitschedtail;
+
+ /*
+ * Next rcu_check_callbacks() will
+ * do the required raise_softirq().
+ */
+ }
+ if (rdp->nextschedlist != NULL) {
+ rdp->waitschedlist = rdp->nextschedlist;
+ rdp->waitschedtail = rdp->nextschedtail;
+ couldsleep = 0;
+ couldsleepnext = 0;
+ } else {
+ rdp->waitschedlist = NULL;
+ rdp->waitschedtail = &rdp->waitschedlist;
+ }
+ rdp->nextschedlist = NULL;
+ rdp->nextschedtail = &rdp->nextschedlist;
+
+ /* Mark sleep intention. */
+
+ rdp->rcu_sched_sleeping = couldsleep;
+
+ spin_unlock_irqrestore(&rdp->lock, flags);
+ }
+
+ /* If we saw callbacks on the last scan, go deal with them. */
+
+ if (!couldsleep)
+ continue;
+
+ /* Attempt to block... */
+
+ spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+ if (rcu_ctrlblk.sched_sleep != rcu_sched_sleep_prep) {
+
+ /*
+ * Someone posted a callback after we scanned.
+ * Go take care of it.
+ */
+ spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+ couldsleepnext = 0;
+ continue;
+ }
+
+ /* Block until the next person posts a callback. */
+
+ rcu_ctrlblk.sched_sleep = rcu_sched_sleeping;
+ spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+ ret = 0;
+ __wait_event_interruptible(rcu_ctrlblk.sched_wq,
+ rcu_ctrlblk.sched_sleep != rcu_sched_sleeping,
+ ret);
+
+ /*
+ * Signals would prevent us from sleeping, and we cannot
+ * do much with them in any case. So flush them.
+ */
+ if (ret)
+ flush_signals(current);
+ couldsleepnext = 0;
+
+ } while (!kthread_should_stop());
+
+ return (0);
}
- EXPORT_SYMBOL_GPL(__synchronize_sched);
/*
* Check to see if any future RCU-related work will need to be done
return (rdp->donelist != NULL ||
!!rdp->waitlistcount ||
- rdp->nextlist != NULL);
+ rdp->nextlist != NULL ||
+ rdp->nextschedlist != NULL ||
+ rdp->waitschedlist != NULL);
}
int rcu_pending(int cpu)
if (rdp->donelist != NULL ||
!!rdp->waitlistcount ||
- rdp->nextlist != NULL)
+ rdp->nextlist != NULL ||
+ rdp->nextschedlist != NULL ||
+ rdp->waitschedlist != NULL)
return 1;
/* The RCU core needs an acknowledgement from this CPU. */
rdp->donetail = &rdp->donelist;
rdp->rcu_flipctr[0] = 0;
rdp->rcu_flipctr[1] = 0;
+ rdp->nextschedlist = NULL;
+ rdp->nextschedtail = &rdp->nextschedlist;
+ rdp->waitschedlist = NULL;
+ rdp->waitschedtail = &rdp->waitschedlist;
+ rdp->rcu_sched_sleeping = 0;
}
register_cpu_notifier(&rcu_nb);
for_each_online_cpu(cpu)
rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu);
- open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
+ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
}
/*
- * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ * Late-boot-time RCU initialization that must wait until after scheduler
+ * has been initialized.
*/
- void synchronize_kernel(void)
+ void __init rcu_init_sched(void)
{
- synchronize_rcu();
+ rcu_sched_grace_period_task = kthread_run(rcu_sched_grace_period,
+ NULL,
+ "rcu_sched_grace_period");
+ WARN_ON(IS_ERR(rcu_sched_grace_period_task));
}
#ifdef CONFIG_RCU_TRACE
projects / linux-2.6-omap-h63xx.git / commitdiff