*/
#include <linux/delay.h>
+#include <linux/oom.h>
+#include <linux/smpboot.h>
#define RCU_KTHREAD_PRIO 1
*/
void rcu_force_quiescent_state(void)
{
- force_quiescent_state(&rcu_preempt_state, 0);
+ force_quiescent_state(&rcu_preempt_state);
}
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
{
struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
- rdp->passed_quiesce_gpnum = rdp->gpnum;
- barrier();
if (rdp->passed_quiesce == 0)
trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs");
rdp->passed_quiesce = 1;
unsigned long flags;
struct task_struct *t;
- if (!rcu_preempt_blocked_readers_cgp(rnp))
- return;
raw_spin_lock_irqsave(&rnp->lock, flags);
+ if (!rcu_preempt_blocked_readers_cgp(rnp)) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
t = list_entry(rnp->gp_tasks,
struct task_struct, rcu_node_entry);
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry)
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
}
+ rnp->gp_tasks = NULL;
+ rnp->exp_tasks = NULL;
#ifdef CONFIG_RCU_BOOST
- /* In case root is being boosted and leaf is not. */
+ rnp->boost_tasks = NULL;
+ /*
+ * In case root is being boosted and leaf was not. Make sure
+ * that we boost the tasks blocking the current grace period
+ * in this case.
+ */
raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
if (rnp_root->boost_tasks != NULL &&
- rnp_root->boost_tasks != rnp_root->gp_tasks)
+ rnp_root->boost_tasks != rnp_root->gp_tasks &&
+ rnp_root->boost_tasks != rnp_root->exp_tasks)
rnp_root->boost_tasks = rnp_root->gp_tasks;
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
#endif /* #ifdef CONFIG_RCU_BOOST */
- rnp->gp_tasks = NULL;
- rnp->exp_tasks = NULL;
return retval;
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
-static long sync_rcu_preempt_exp_count;
+static unsigned long sync_rcu_preempt_exp_count;
static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
/*
unsigned long flags;
struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_preempt_state;
- long snap;
+ unsigned long snap;
int trycount = 0;
smp_mb(); /* Caller's modifications seen first by other CPUs. */
snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1;
smp_mb(); /* Above access cannot bleed into critical section. */
+ /*
+ * Block CPU-hotplug operations. This means that any CPU-hotplug
+ * operation that finds an rcu_node structure with tasks in the
+ * process of being boosted will know that all tasks blocking
+ * this expedited grace period will already be in the process of
+ * being boosted. This simplifies the process of moving tasks
+ * from leaf to root rcu_node structures.
+ */
+ get_online_cpus();
+
/*
* Acquire lock, falling back to synchronize_rcu() if too many
* lock-acquisition failures. Of course, if someone does the
* expedited grace period for us, just leave.
*/
while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
+ if (ULONG_CMP_LT(snap,
+ ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
+ put_online_cpus();
+ goto mb_ret; /* Others did our work for us. */
+ }
if (trycount++ < 10) {
udelay(trycount * num_online_cpus());
} else {
+ put_online_cpus();
synchronize_rcu();
return;
}
- if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
- goto mb_ret; /* Others did our work for us. */
}
- if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
+ if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
+ put_online_cpus();
goto unlock_mb_ret; /* Others did our work for us. */
+ }
/* force all RCU readers onto ->blkd_tasks lists. */
synchronize_sched_expedited();
- raw_spin_lock_irqsave(&rsp->onofflock, flags);
-
/* Initialize ->expmask for all non-leaf rcu_node structures. */
rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ raw_spin_lock_irqsave(&rnp->lock, flags);
rnp->expmask = rnp->qsmaskinit;
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/* Snapshot current state of ->blkd_tasks lists. */
if (NUM_RCU_NODES > 1)
sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
- raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
+ put_online_cpus();
/* Wait for snapshotted ->blkd_tasks lists to drain. */
rnp = rcu_get_root(rsp);
#endif /* #else #ifdef CONFIG_RCU_TRACE */
+static void rcu_wake_cond(struct task_struct *t, int status)
+{
+ /*
+ * If the thread is yielding, only wake it when this
+ * is invoked from idle
+ */
+ if (status != RCU_KTHREAD_YIELDING || is_idle_task(current))
+ wake_up_process(t);
+}
+
/*
* Carry out RCU priority boosting on the task indicated by ->exp_tasks
* or ->boost_tasks, advancing the pointer to the next task in the
ACCESS_ONCE(rnp->boost_tasks) != NULL;
}
-/*
- * Timer handler to initiate waking up of boost kthreads that
- * have yielded the CPU due to excessive numbers of tasks to
- * boost. We wake up the per-rcu_node kthread, which in turn
- * will wake up the booster kthread.
- */
-static void rcu_boost_kthread_timer(unsigned long arg)
-{
- invoke_rcu_node_kthread((struct rcu_node *)arg);
-}
-
/*
* Priority-boosting kthread. One per leaf rcu_node and one for the
* root rcu_node.
else
spincnt = 0;
if (spincnt > 10) {
+ rnp->boost_kthread_status = RCU_KTHREAD_YIELDING;
trace_rcu_utilization("End boost kthread@rcu_yield");
- rcu_yield(rcu_boost_kthread_timer, (unsigned long)rnp);
+ schedule_timeout_interruptible(2);
trace_rcu_utilization("Start boost kthread@rcu_yield");
spincnt = 0;
}
* kthread to start boosting them. If there is an expedited grace
* period in progress, it is always time to boost.
*
- * The caller must hold rnp->lock, which this function releases,
- * but irqs remain disabled. The ->boost_kthread_task is immortal,
- * so we don't need to worry about it going away.
+ * The caller must hold rnp->lock, which this function releases.
+ * The ->boost_kthread_task is immortal, so we don't need to worry
+ * about it going away.
*/
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
{
rnp->boost_tasks = rnp->gp_tasks;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
t = rnp->boost_kthread_task;
- if (t != NULL)
- wake_up_process(t);
+ if (t)
+ rcu_wake_cond(t, rnp->boost_kthread_status);
} else {
rcu_initiate_boost_trace(rnp);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
local_irq_save(flags);
__this_cpu_write(rcu_cpu_has_work, 1);
if (__this_cpu_read(rcu_cpu_kthread_task) != NULL &&
- current != __this_cpu_read(rcu_cpu_kthread_task))
- wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
+ current != __this_cpu_read(rcu_cpu_kthread_task)) {
+ rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task),
+ __this_cpu_read(rcu_cpu_kthread_status));
+ }
local_irq_restore(flags);
}
return __get_cpu_var(rcu_cpu_kthread_task) == current;
}
-/*
- * Set the affinity of the boost kthread. The CPU-hotplug locks are
- * held, so no one should be messing with the existence of the boost
- * kthread.
- */
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
- cpumask_var_t cm)
-{
- struct task_struct *t;
-
- t = rnp->boost_kthread_task;
- if (t != NULL)
- set_cpus_allowed_ptr(rnp->boost_kthread_task, cm);
-}
-
#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
/*
* Returns zero if all is well, a negated errno otherwise.
*/
static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
- struct rcu_node *rnp,
- int rnp_index)
+ struct rcu_node *rnp)
{
+ int rnp_index = rnp - &rsp->node[0];
unsigned long flags;
struct sched_param sp;
struct task_struct *t;
if (&rcu_preempt_state != rsp)
return 0;
+
+ if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
+ return 0;
+
rsp->boost = 1;
if (rnp->boost_kthread_task != NULL)
return 0;
return 0;
}
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Stop the RCU's per-CPU kthread when its CPU goes offline,.
- */
-static void rcu_stop_cpu_kthread(int cpu)
-{
- struct task_struct *t;
-
- /* Stop the CPU's kthread. */
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (t != NULL) {
- per_cpu(rcu_cpu_kthread_task, cpu) = NULL;
- kthread_stop(t);
- }
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
static void rcu_kthread_do_work(void)
{
rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data));
rcu_preempt_do_callbacks();
}
-/*
- * Wake up the specified per-rcu_node-structure kthread.
- * Because the per-rcu_node kthreads are immortal, we don't need
- * to do anything to keep them alive.
- */
-static void invoke_rcu_node_kthread(struct rcu_node *rnp)
-{
- struct task_struct *t;
-
- t = rnp->node_kthread_task;
- if (t != NULL)
- wake_up_process(t);
-}
-
-/*
- * Set the specified CPU's kthread to run RT or not, as specified by
- * the to_rt argument. The CPU-hotplug locks are held, so the task
- * is not going away.
- */
-static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
+static void rcu_cpu_kthread_setup(unsigned int cpu)
{
- int policy;
struct sched_param sp;
- struct task_struct *t;
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (t == NULL)
- return;
- if (to_rt) {
- policy = SCHED_FIFO;
- sp.sched_priority = RCU_KTHREAD_PRIO;
- } else {
- policy = SCHED_NORMAL;
- sp.sched_priority = 0;
- }
- sched_setscheduler_nocheck(t, policy, &sp);
+ sp.sched_priority = RCU_KTHREAD_PRIO;
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
}
-/*
- * Timer handler to initiate the waking up of per-CPU kthreads that
- * have yielded the CPU due to excess numbers of RCU callbacks.
- * We wake up the per-rcu_node kthread, which in turn will wake up
- * the booster kthread.
- */
-static void rcu_cpu_kthread_timer(unsigned long arg)
+static void rcu_cpu_kthread_park(unsigned int cpu)
{
- struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
- struct rcu_node *rnp = rdp->mynode;
-
- atomic_or(rdp->grpmask, &rnp->wakemask);
- invoke_rcu_node_kthread(rnp);
+ per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
}
-/*
- * Drop to non-real-time priority and yield, but only after posting a
- * timer that will cause us to regain our real-time priority if we
- * remain preempted. Either way, we restore our real-time priority
- * before returning.
- */
-static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
+static int rcu_cpu_kthread_should_run(unsigned int cpu)
{
- struct sched_param sp;
- struct timer_list yield_timer;
- int prio = current->rt_priority;
-
- setup_timer_on_stack(&yield_timer, f, arg);
- mod_timer(&yield_timer, jiffies + 2);
- sp.sched_priority = 0;
- sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
- set_user_nice(current, 19);
- schedule();
- set_user_nice(current, 0);
- sp.sched_priority = prio;
- sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
- del_timer(&yield_timer);
-}
-
-/*
- * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU.
- * This can happen while the corresponding CPU is either coming online
- * or going offline. We cannot wait until the CPU is fully online
- * before starting the kthread, because the various notifier functions
- * can wait for RCU grace periods. So we park rcu_cpu_kthread() until
- * the corresponding CPU is online.
- *
- * Return 1 if the kthread needs to stop, 0 otherwise.
- *
- * Caller must disable bh. This function can momentarily enable it.
- */
-static int rcu_cpu_kthread_should_stop(int cpu)
-{
- while (cpu_is_offline(cpu) ||
- !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) ||
- smp_processor_id() != cpu) {
- if (kthread_should_stop())
- return 1;
- per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
- per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id();
- local_bh_enable();
- schedule_timeout_uninterruptible(1);
- if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)))
- set_cpus_allowed_ptr(current, cpumask_of(cpu));
- local_bh_disable();
- }
- per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
- return 0;
+ return __get_cpu_var(rcu_cpu_has_work);
}
/*
* RCU softirq used in flavors and configurations of RCU that do not
* support RCU priority boosting.
*/
-static int rcu_cpu_kthread(void *arg)
+static void rcu_cpu_kthread(unsigned int cpu)
{
- int cpu = (int)(long)arg;
- unsigned long flags;
- int spincnt = 0;
- unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
- char work;
- char *workp = &per_cpu(rcu_cpu_has_work, cpu);
+ unsigned int *statusp = &__get_cpu_var(rcu_cpu_kthread_status);
+ char work, *workp = &__get_cpu_var(rcu_cpu_has_work);
+ int spincnt;
- trace_rcu_utilization("Start CPU kthread@init");
- for (;;) {
- *statusp = RCU_KTHREAD_WAITING;
- trace_rcu_utilization("End CPU kthread@rcu_wait");
- rcu_wait(*workp != 0 || kthread_should_stop());
+ for (spincnt = 0; spincnt < 10; spincnt++) {
trace_rcu_utilization("Start CPU kthread@rcu_wait");
local_bh_disable();
- if (rcu_cpu_kthread_should_stop(cpu)) {
- local_bh_enable();
- break;
- }
*statusp = RCU_KTHREAD_RUNNING;
- per_cpu(rcu_cpu_kthread_loops, cpu)++;
- local_irq_save(flags);
+ this_cpu_inc(rcu_cpu_kthread_loops);
+ local_irq_disable();
work = *workp;
*workp = 0;
- local_irq_restore(flags);
+ local_irq_enable();
if (work)
rcu_kthread_do_work();
local_bh_enable();
- if (*workp != 0)
- spincnt++;
- else
- spincnt = 0;
- if (spincnt > 10) {
- *statusp = RCU_KTHREAD_YIELDING;
- trace_rcu_utilization("End CPU kthread@rcu_yield");
- rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
- trace_rcu_utilization("Start CPU kthread@rcu_yield");
- spincnt = 0;
- }
- }
- *statusp = RCU_KTHREAD_STOPPED;
- trace_rcu_utilization("End CPU kthread@term");
- return 0;
-}
-
-/*
- * Spawn a per-CPU kthread, setting up affinity and priority.
- * Because the CPU hotplug lock is held, no other CPU will be attempting
- * to manipulate rcu_cpu_kthread_task. There might be another CPU
- * attempting to access it during boot, but the locking in kthread_bind()
- * will enforce sufficient ordering.
- *
- * Please note that we cannot simply refuse to wake up the per-CPU
- * kthread because kthreads are created in TASK_UNINTERRUPTIBLE state,
- * which can result in softlockup complaints if the task ends up being
- * idle for more than a couple of minutes.
- *
- * However, please note also that we cannot bind the per-CPU kthread to its
- * CPU until that CPU is fully online. We also cannot wait until the
- * CPU is fully online before we create its per-CPU kthread, as this would
- * deadlock the system when CPU notifiers tried waiting for grace
- * periods. So we bind the per-CPU kthread to its CPU only if the CPU
- * is online. If its CPU is not yet fully online, then the code in
- * rcu_cpu_kthread() will wait until it is fully online, and then do
- * the binding.
- */
-static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
-{
- struct sched_param sp;
- struct task_struct *t;
-
- if (!rcu_scheduler_fully_active ||
- per_cpu(rcu_cpu_kthread_task, cpu) != NULL)
- return 0;
- t = kthread_create_on_node(rcu_cpu_kthread,
- (void *)(long)cpu,
- cpu_to_node(cpu),
- "rcuc/%d", cpu);
- if (IS_ERR(t))
- return PTR_ERR(t);
- if (cpu_online(cpu))
- kthread_bind(t, cpu);
- per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
- WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- per_cpu(rcu_cpu_kthread_task, cpu) = t;
- wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */
- return 0;
-}
-
-/*
- * Per-rcu_node kthread, which is in charge of waking up the per-CPU
- * kthreads when needed. We ignore requests to wake up kthreads
- * for offline CPUs, which is OK because force_quiescent_state()
- * takes care of this case.
- */
-static int rcu_node_kthread(void *arg)
-{
- int cpu;
- unsigned long flags;
- unsigned long mask;
- struct rcu_node *rnp = (struct rcu_node *)arg;
- struct sched_param sp;
- struct task_struct *t;
-
- for (;;) {
- rnp->node_kthread_status = RCU_KTHREAD_WAITING;
- rcu_wait(atomic_read(&rnp->wakemask) != 0);
- rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- mask = atomic_xchg(&rnp->wakemask, 0);
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
- if ((mask & 0x1) == 0)
- continue;
- preempt_disable();
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (!cpu_online(cpu) || t == NULL) {
- preempt_enable();
- continue;
- }
- per_cpu(rcu_cpu_has_work, cpu) = 1;
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- preempt_enable();
+ if (*workp == 0) {
+ trace_rcu_utilization("End CPU kthread@rcu_wait");
+ *statusp = RCU_KTHREAD_WAITING;
+ return;
}
}
- /* NOTREACHED */
- rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
- return 0;
+ *statusp = RCU_KTHREAD_YIELDING;
+ trace_rcu_utilization("Start CPU kthread@rcu_yield");
+ schedule_timeout_interruptible(2);
+ trace_rcu_utilization("End CPU kthread@rcu_yield");
+ *statusp = RCU_KTHREAD_WAITING;
}
/*
* no outgoing CPU. If there are no CPUs left in the affinity set,
* this function allows the kthread to execute on any CPU.
*/
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
{
+ struct task_struct *t = rnp->boost_kthread_task;
+ unsigned long mask = rnp->qsmaskinit;
cpumask_var_t cm;
int cpu;
- unsigned long mask = rnp->qsmaskinit;
- if (rnp->node_kthread_task == NULL)
+ if (!t)
return;
- if (!alloc_cpumask_var(&cm, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&cm, GFP_KERNEL))
return;
- cpumask_clear(cm);
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
if ((mask & 0x1) && cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm);
cpumask_clear_cpu(cpu, cm);
WARN_ON_ONCE(cpumask_weight(cm) == 0);
}
- set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
- rcu_boost_kthread_setaffinity(rnp, cm);
+ set_cpus_allowed_ptr(t, cm);
free_cpumask_var(cm);
}
-/*
- * Spawn a per-rcu_node kthread, setting priority and affinity.
- * Called during boot before online/offline can happen, or, if
- * during runtime, with the main CPU-hotplug locks held. So only
- * one of these can be executing at a time.
- */
-static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
- struct rcu_node *rnp)
-{
- unsigned long flags;
- int rnp_index = rnp - &rsp->node[0];
- struct sched_param sp;
- struct task_struct *t;
-
- if (!rcu_scheduler_fully_active ||
- rnp->qsmaskinit == 0)
- return 0;
- if (rnp->node_kthread_task == NULL) {
- t = kthread_create(rcu_node_kthread, (void *)rnp,
- "rcun/%d", rnp_index);
- if (IS_ERR(t))
- return PTR_ERR(t);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rnp->node_kthread_task = t;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- sp.sched_priority = 99;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
- }
- return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
-}
+static struct smp_hotplug_thread rcu_cpu_thread_spec = {
+ .store = &rcu_cpu_kthread_task,
+ .thread_should_run = rcu_cpu_kthread_should_run,
+ .thread_fn = rcu_cpu_kthread,
+ .thread_comm = "rcuc/%u",
+ .setup = rcu_cpu_kthread_setup,
+ .park = rcu_cpu_kthread_park,
+};
/*
* Spawn all kthreads -- called as soon as the scheduler is running.
*/
static int __init rcu_spawn_kthreads(void)
{
- int cpu;
struct rcu_node *rnp;
+ int cpu;
rcu_scheduler_fully_active = 1;
- for_each_possible_cpu(cpu) {
+ for_each_possible_cpu(cpu)
per_cpu(rcu_cpu_has_work, cpu) = 0;
- if (cpu_online(cpu))
- (void)rcu_spawn_one_cpu_kthread(cpu);
- }
+ BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
rnp = rcu_get_root(rcu_state);
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+ (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
if (NUM_RCU_NODES > 1) {
rcu_for_each_leaf_node(rcu_state, rnp)
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
+ (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
}
return 0;
}
struct rcu_node *rnp = rdp->mynode;
/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
- if (rcu_scheduler_fully_active) {
- (void)rcu_spawn_one_cpu_kthread(cpu);
- if (rnp->node_kthread_task == NULL)
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
- }
+ if (rcu_scheduler_fully_active)
+ (void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
}
#else /* #ifdef CONFIG_RCU_BOOST */
{
}
-#ifdef CONFIG_HOTPLUG_CPU
-
-static void rcu_stop_cpu_kthread(int cpu)
-{
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
-{
-}
-
-static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
{
}
if (!tne)
return;
+ /* Adaptive-tick mode, where usermode execution is idle to RCU. */
+ if (!is_idle_task(current)) {
+ rdtp->dyntick_holdoff = jiffies - 1;
+ if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
+ trace_rcu_prep_idle("User dyntick with callbacks");
+ rdtp->idle_gp_timer_expires =
+ round_up(jiffies + RCU_IDLE_GP_DELAY,
+ RCU_IDLE_GP_DELAY);
+ } else if (rcu_cpu_has_callbacks(cpu)) {
+ rdtp->idle_gp_timer_expires =
+ round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY);
+ trace_rcu_prep_idle("User dyntick with lazy callbacks");
+ } else {
+ return;
+ }
+ tp = &rdtp->idle_gp_timer;
+ mod_timer_pinned(tp, rdtp->idle_gp_timer_expires);
+ return;
+ }
+
/*
* If this is an idle re-entry, for example, due to use of
* RCU_NONIDLE() or the new idle-loop tracing API within the idle
#ifdef CONFIG_TREE_PREEMPT_RCU
if (per_cpu(rcu_preempt_data, cpu).nxtlist) {
rcu_preempt_qs(cpu);
- force_quiescent_state(&rcu_preempt_state, 0);
+ force_quiescent_state(&rcu_preempt_state);
}
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
if (per_cpu(rcu_sched_data, cpu).nxtlist) {
rcu_sched_qs(cpu);
- force_quiescent_state(&rcu_sched_state, 0);
+ force_quiescent_state(&rcu_sched_state);
}
if (per_cpu(rcu_bh_data, cpu).nxtlist) {
rcu_bh_qs(cpu);
- force_quiescent_state(&rcu_bh_state, 0);
+ force_quiescent_state(&rcu_bh_state);
}
/*
__this_cpu_add(rcu_dynticks.nonlazy_posted, 1);
}
+/*
+ * Data for flushing lazy RCU callbacks at OOM time.
+ */
+static atomic_t oom_callback_count;
+static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq);
+
+/*
+ * RCU OOM callback -- decrement the outstanding count and deliver the
+ * wake-up if we are the last one.
+ */
+static void rcu_oom_callback(struct rcu_head *rhp)
+{
+ if (atomic_dec_and_test(&oom_callback_count))
+ wake_up(&oom_callback_wq);
+}
+
+/*
+ * Post an rcu_oom_notify callback on the current CPU if it has at
+ * least one lazy callback. This will unnecessarily post callbacks
+ * to CPUs that already have a non-lazy callback at the end of their
+ * callback list, but this is an infrequent operation, so accept some
+ * extra overhead to keep things simple.
+ */
+static void rcu_oom_notify_cpu(void *unused)
+{
+ struct rcu_state *rsp;
+ struct rcu_data *rdp;
+
+ for_each_rcu_flavor(rsp) {
+ rdp = __this_cpu_ptr(rsp->rda);
+ if (rdp->qlen_lazy != 0) {
+ atomic_inc(&oom_callback_count);
+ rsp->call(&rdp->oom_head, rcu_oom_callback);
+ }
+ }
+}
+
+/*
+ * If low on memory, ensure that each CPU has a non-lazy callback.
+ * This will wake up CPUs that have only lazy callbacks, in turn
+ * ensuring that they free up the corresponding memory in a timely manner.
+ * Because an uncertain amount of memory will be freed in some uncertain
+ * timeframe, we do not claim to have freed anything.
+ */
+static int rcu_oom_notify(struct notifier_block *self,
+ unsigned long notused, void *nfreed)
+{
+ int cpu;
+
+ /* Wait for callbacks from earlier instance to complete. */
+ wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0);
+
+ /*
+ * Prevent premature wakeup: ensure that all increments happen
+ * before there is a chance of the counter reaching zero.
+ */
+ atomic_set(&oom_callback_count, 1);
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
+ cond_resched();
+ }
+ put_online_cpus();
+
+ /* Unconditionally decrement: no need to wake ourselves up. */
+ atomic_dec(&oom_callback_count);
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block rcu_oom_nb = {
+ .notifier_call = rcu_oom_notify
+};
+
+static int __init rcu_register_oom_notifier(void)
+{
+ register_oom_notifier(&rcu_oom_nb);
+ return 0;
+}
+early_initcall(rcu_register_oom_notifier);
+
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
#ifdef CONFIG_RCU_CPU_STALL_INFO
{
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
struct timer_list *tltp = &rdtp->idle_gp_timer;
+ char c;
- sprintf(cp, "drain=%d %c timer=%lu",
- rdtp->dyntick_drain,
- rdtp->dyntick_holdoff == jiffies ? 'H' : '.',
- timer_pending(tltp) ? tltp->expires - jiffies : -1);
+ c = rdtp->dyntick_holdoff == jiffies ? 'H' : '.';
+ if (timer_pending(tltp))
+ sprintf(cp, "drain=%d %c timer=%lu",
+ rdtp->dyntick_drain, c, tltp->expires - jiffies);
+ else
+ sprintf(cp, "drain=%d %c timer not pending",
+ rdtp->dyntick_drain, c);
}
#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
/* Increment ->ticks_this_gp for all flavors of RCU. */
static void increment_cpu_stall_ticks(void)
{
- __get_cpu_var(rcu_sched_data).ticks_this_gp++;
- __get_cpu_var(rcu_bh_data).ticks_this_gp++;
-#ifdef CONFIG_TREE_PREEMPT_RCU
- __get_cpu_var(rcu_preempt_data).ticks_this_gp++;
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+ struct rcu_state *rsp;
+
+ for_each_rcu_flavor(rsp)
+ __this_cpu_ptr(rsp->rda)->ticks_this_gp++;
}
#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
projects / ~andy / linux / blobdiff