rcu: priority boosting for TREE_PREEMPT_RCU
Add priority boosting for TREE_PREEMPT_RCU, similar to that for TINY_PREEMPT_RCU. This is enabled by the default-off RCU_BOOST kernel parameter. The priority to which to boost preempted RCU readers is controlled by the RCU_BOOST_PRIO kernel parameter (defaulting to real-time priority 1) and the time to wait before boosting the readers who are blocking a given grace period is controlled by the RCU_BOOST_DELAY kernel parameter (defaulting to 500 milliseconds). Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney
Paul E. McKenney
Родитель
a26ac2455f
Коммит
27f4d28057
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@ -485,7 +485,7 @@ config TREE_RCU_TRACE
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config RCU_BOOST
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bool "Enable RCU priority boosting"
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depends on RT_MUTEXES && TINY_PREEMPT_RCU
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depends on RT_MUTEXES && PREEMPT_RCU
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default n
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help
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This option boosts the priority of preempted RCU readers that
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115
kernel/rcutree.c
115
kernel/rcutree.c
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@ -81,6 +81,8 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
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struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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static struct rcu_state *rcu_state;
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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@ -94,7 +96,7 @@ static DEFINE_PER_CPU(char, rcu_cpu_has_work);
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static char rcu_kthreads_spawnable;
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp);
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static void invoke_rcu_kthread(void);
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static void invoke_rcu_cpu_kthread(void);
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#define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */
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@ -791,6 +793,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
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rnp->completed = rsp->completed;
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rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
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rcu_start_gp_per_cpu(rsp, rnp, rdp);
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rcu_preempt_boost_start_gp(rnp);
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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return;
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}
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@ -826,6 +829,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
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rnp->completed = rsp->completed;
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if (rnp == rdp->mynode)
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rcu_start_gp_per_cpu(rsp, rnp, rdp);
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rcu_preempt_boost_start_gp(rnp);
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raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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}
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@ -882,7 +886,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
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return;
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}
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rnp->qsmask &= ~mask;
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if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
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if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
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/* Other bits still set at this level, so done. */
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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@ -1089,8 +1093,11 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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t = rnp->node_kthread_task;
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if (t != NULL &&
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rnp->qsmaskinit == 0) {
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kthread_stop(t);
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raw_spin_lock_irqsave(&rnp->lock, flags);
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rnp->node_kthread_task = NULL;
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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kthread_stop(t);
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rcu_stop_boost_kthread(rnp);
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} else
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rcu_node_kthread_setaffinity(rnp);
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}
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@ -1190,7 +1197,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
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/* Re-raise the RCU softirq if there are callbacks remaining. */
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if (cpu_has_callbacks_ready_to_invoke(rdp))
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invoke_rcu_kthread();
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invoke_rcu_cpu_kthread();
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}
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/*
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@ -1236,7 +1243,7 @@ void rcu_check_callbacks(int cpu, int user)
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}
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rcu_preempt_check_callbacks(cpu);
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if (rcu_pending(cpu))
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invoke_rcu_kthread();
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invoke_rcu_cpu_kthread();
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}
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#ifdef CONFIG_SMP
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@ -1244,6 +1251,8 @@ void rcu_check_callbacks(int cpu, int user)
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/*
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* Scan the leaf rcu_node structures, processing dyntick state for any that
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* have not yet encountered a quiescent state, using the function specified.
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* Also initiate boosting for any threads blocked on the root rcu_node.
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*
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* The caller must have suppressed start of new grace periods.
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*/
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static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
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@ -1262,6 +1271,7 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
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return;
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}
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if (rnp->qsmask == 0) {
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rcu_initiate_boost(rnp);
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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continue;
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}
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@ -1280,6 +1290,11 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
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}
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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}
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rnp = rcu_get_root(rsp);
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raw_spin_lock_irqsave(&rnp->lock, flags);
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if (rnp->qsmask == 0)
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rcu_initiate_boost(rnp);
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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}
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/*
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@ -1417,7 +1432,7 @@ static void rcu_process_callbacks(void)
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* the current CPU with interrupts disabled, the rcu_cpu_kthread_task
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* cannot disappear out from under us.
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*/
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static void invoke_rcu_kthread(void)
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static void invoke_rcu_cpu_kthread(void)
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{
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unsigned long flags;
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wait_queue_head_t *q;
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@ -1435,25 +1450,34 @@ static void invoke_rcu_kthread(void)
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local_irq_restore(flags);
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}
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/*
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* Wake up the specified per-rcu_node-structure kthread.
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* The caller must hold ->lock.
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*/
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static void invoke_rcu_node_kthread(struct rcu_node *rnp)
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{
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struct task_struct *t;
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t = rnp->node_kthread_task;
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if (t != NULL)
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wake_up_process(t);
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}
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/*
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* Timer handler to initiate the waking up of per-CPU kthreads that
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* have yielded the CPU due to excess numbers of RCU callbacks.
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* We wake up the per-rcu_node kthread, which in turn will wake up
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* the booster kthread.
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*/
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static void rcu_cpu_kthread_timer(unsigned long arg)
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{
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unsigned long flags;
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struct rcu_data *rdp = (struct rcu_data *)arg;
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struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
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struct rcu_node *rnp = rdp->mynode;
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struct task_struct *t;
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raw_spin_lock_irqsave(&rnp->lock, flags);
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rnp->wakemask |= rdp->grpmask;
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t = rnp->node_kthread_task;
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if (t == NULL) {
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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return;
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}
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wake_up_process(t);
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invoke_rcu_node_kthread(rnp);
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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}
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@ -1463,13 +1487,12 @@ static void rcu_cpu_kthread_timer(unsigned long arg)
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* remain preempted. Either way, we restore our real-time priority
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* before returning.
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*/
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static void rcu_yield(int cpu)
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static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
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{
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struct rcu_data *rdp = per_cpu_ptr(rcu_sched_state.rda, cpu);
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struct sched_param sp;
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struct timer_list yield_timer;
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setup_timer_on_stack(&yield_timer, rcu_cpu_kthread_timer, (unsigned long)rdp);
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setup_timer_on_stack(&yield_timer, f, arg);
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mod_timer(&yield_timer, jiffies + 2);
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sp.sched_priority = 0;
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sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
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@ -1540,7 +1563,7 @@ static int rcu_cpu_kthread(void *arg)
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else
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spincnt = 0;
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if (spincnt > 10) {
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rcu_yield(cpu);
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rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
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spincnt = 0;
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}
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}
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@ -1597,6 +1620,7 @@ static int rcu_node_kthread(void *arg)
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raw_spin_lock_irqsave(&rnp->lock, flags);
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mask = rnp->wakemask;
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rnp->wakemask = 0;
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rcu_initiate_boost(rnp);
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
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if ((mask & 0x1) == 0)
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@ -1618,7 +1642,8 @@ static int rcu_node_kthread(void *arg)
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/*
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* Set the per-rcu_node kthread's affinity to cover all CPUs that are
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* served by the rcu_node in question.
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* served by the rcu_node in question. The CPU hotplug lock is still
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* held, so the value of rnp->qsmaskinit will be stable.
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*/
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp)
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{
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@ -1626,8 +1651,7 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp)
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int cpu;
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unsigned long mask = rnp->qsmaskinit;
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if (rnp->node_kthread_task == NULL ||
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rnp->qsmaskinit == 0)
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if (rnp->node_kthread_task == NULL || mask == 0)
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return;
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if (!alloc_cpumask_var(&cm, GFP_KERNEL))
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return;
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@ -1636,31 +1660,40 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp)
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if (mask & 0x1)
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cpumask_set_cpu(cpu, cm);
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set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
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rcu_boost_kthread_setaffinity(rnp, cm);
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free_cpumask_var(cm);
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}
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/*
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* Spawn a per-rcu_node kthread, setting priority and affinity.
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* Called during boot before online/offline can happen, or, if
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* during runtime, with the main CPU-hotplug locks held. So only
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* one of these can be executing at a time.
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*/
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static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
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struct rcu_node *rnp)
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{
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unsigned long flags;
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int rnp_index = rnp - &rsp->node[0];
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struct sched_param sp;
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struct task_struct *t;
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if (!rcu_kthreads_spawnable ||
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rnp->qsmaskinit == 0 ||
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rnp->node_kthread_task != NULL)
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rnp->qsmaskinit == 0)
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return 0;
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t = kthread_create(rcu_node_kthread, (void *)rnp, "rcun%d", rnp_index);
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if (IS_ERR(t))
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return PTR_ERR(t);
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rnp->node_kthread_task = t;
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wake_up_process(t);
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sp.sched_priority = 99;
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sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
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return 0;
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if (rnp->node_kthread_task == NULL) {
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t = kthread_create(rcu_node_kthread, (void *)rnp,
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"rcun%d", rnp_index);
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if (IS_ERR(t))
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return PTR_ERR(t);
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raw_spin_lock_irqsave(&rnp->lock, flags);
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rnp->node_kthread_task = t;
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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wake_up_process(t);
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sp.sched_priority = 99;
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sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
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}
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return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
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}
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/*
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@ -1678,10 +1711,16 @@ static int __init rcu_spawn_kthreads(void)
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if (cpu_online(cpu))
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(void)rcu_spawn_one_cpu_kthread(cpu);
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}
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rcu_for_each_leaf_node(&rcu_sched_state, rnp) {
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init_waitqueue_head(&rnp->node_wq);
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(void)rcu_spawn_one_node_kthread(&rcu_sched_state, rnp);
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}
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rnp = rcu_get_root(rcu_state);
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init_waitqueue_head(&rnp->node_wq);
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rcu_init_boost_waitqueue(rnp);
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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if (NUM_RCU_NODES > 1)
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rcu_for_each_leaf_node(rcu_state, rnp) {
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init_waitqueue_head(&rnp->node_wq);
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rcu_init_boost_waitqueue(rnp);
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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}
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return 0;
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}
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early_initcall(rcu_spawn_kthreads);
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@ -2087,14 +2126,14 @@ static void __cpuinit rcu_online_cpu(int cpu)
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static void __cpuinit rcu_online_kthreads(int cpu)
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{
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struct rcu_data *rdp = per_cpu_ptr(rcu_sched_state.rda, cpu);
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struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
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struct rcu_node *rnp = rdp->mynode;
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/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
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if (rcu_kthreads_spawnable) {
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(void)rcu_spawn_one_cpu_kthread(cpu);
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if (rnp->node_kthread_task == NULL)
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(void)rcu_spawn_one_node_kthread(&rcu_sched_state, rnp);
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(void)rcu_spawn_one_node_kthread(rcu_state, rnp);
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}
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}
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@ -2105,7 +2144,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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long cpu = (long)hcpu;
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struct rcu_data *rdp = per_cpu_ptr(rcu_sched_state.rda, cpu);
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struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
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struct rcu_node *rnp = rdp->mynode;
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switch (action) {
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@ -135,6 +135,24 @@ struct rcu_node {
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/* if there is no such task. If there */
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/* is no current expedited grace period, */
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/* then there can cannot be any such task. */
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#ifdef CONFIG_RCU_BOOST
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struct list_head *boost_tasks;
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/* Pointer to first task that needs to be */
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/* priority boosted, or NULL if no priority */
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/* boosting is needed for this rcu_node */
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/* structure. If there are no tasks */
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/* queued on this rcu_node structure that */
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/* are blocking the current grace period, */
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/* there can be no such task. */
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unsigned long boost_time;
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/* When to start boosting (jiffies). */
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struct task_struct *boost_kthread_task;
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/* kthread that takes care of priority */
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/* boosting for this rcu_node structure. */
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wait_queue_head_t boost_wq;
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/* Wait queue on which to park the boost */
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/* kthread. */
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#endif /* #ifdef CONFIG_RCU_BOOST */
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struct task_struct *node_kthread_task;
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/* kthread that takes care of this rcu_node */
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/* structure, for example, awakening the */
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@ -365,7 +383,7 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
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static void rcu_bootup_announce(void);
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long rcu_batches_completed(void);
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static void rcu_preempt_note_context_switch(int cpu);
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static int rcu_preempted_readers(struct rcu_node *rnp);
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static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
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#ifdef CONFIG_HOTPLUG_CPU
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static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
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unsigned long flags);
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@ -392,5 +410,16 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
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static void rcu_preempt_send_cbs_to_online(void);
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static void __init __rcu_init_preempt(void);
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static void rcu_needs_cpu_flush(void);
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static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp);
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static void rcu_initiate_boost(struct rcu_node *rnp);
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static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
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cpumask_var_t cm);
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static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
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static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
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struct rcu_node *rnp,
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int rnp_index);
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#ifdef CONFIG_HOTPLUG_CPU
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static void rcu_stop_boost_kthread(struct rcu_node *rnp);
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#endif /* #ifdef CONFIG_HOTPLUG_CPU */
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#endif /* #ifndef RCU_TREE_NONCORE */
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@ -66,6 +66,7 @@ static void __init rcu_bootup_announce_oddness(void)
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struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
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static struct rcu_state *rcu_state = &rcu_preempt_state;
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|
||||
static int rcu_preempted_readers_exp(struct rcu_node *rnp);
|
||||
|
||||
|
|
@ -179,6 +180,10 @@ static void rcu_preempt_note_context_switch(int cpu)
|
|||
if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) {
|
||||
list_add(&t->rcu_node_entry, rnp->gp_tasks->prev);
|
||||
rnp->gp_tasks = &t->rcu_node_entry;
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
if (rnp->boost_tasks != NULL)
|
||||
rnp->boost_tasks = rnp->gp_tasks;
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
} else {
|
||||
list_add(&t->rcu_node_entry, &rnp->blkd_tasks);
|
||||
if (rnp->qsmask & rdp->grpmask)
|
||||
|
|
@ -218,7 +223,7 @@ EXPORT_SYMBOL_GPL(__rcu_read_lock);
|
|||
* for the specified rcu_node structure. If the caller needs a reliable
|
||||
* answer, it must hold the rcu_node's ->lock.
|
||||
*/
|
||||
static int rcu_preempted_readers(struct rcu_node *rnp)
|
||||
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
|
||||
{
|
||||
return rnp->gp_tasks != NULL;
|
||||
}
|
||||
|
|
@ -236,7 +241,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
|
|||
unsigned long mask;
|
||||
struct rcu_node *rnp_p;
|
||||
|
||||
if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
|
||||
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
return; /* Still need more quiescent states! */
|
||||
}
|
||||
|
|
@ -325,7 +330,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
|
|||
break;
|
||||
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
||||
}
|
||||
empty = !rcu_preempted_readers(rnp);
|
||||
empty = !rcu_preempt_blocked_readers_cgp(rnp);
|
||||
empty_exp = !rcu_preempted_readers_exp(rnp);
|
||||
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
|
||||
np = rcu_next_node_entry(t, rnp);
|
||||
|
|
@ -334,6 +339,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
|
|||
rnp->gp_tasks = np;
|
||||
if (&t->rcu_node_entry == rnp->exp_tasks)
|
||||
rnp->exp_tasks = np;
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
if (&t->rcu_node_entry == rnp->boost_tasks)
|
||||
rnp->boost_tasks = np;
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
t->rcu_blocked_node = NULL;
|
||||
|
||||
/*
|
||||
|
|
@ -346,6 +355,15 @@ static void rcu_read_unlock_special(struct task_struct *t)
|
|||
else
|
||||
rcu_report_unblock_qs_rnp(rnp, flags);
|
||||
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
/* Unboost if we were boosted. */
|
||||
if (special & RCU_READ_UNLOCK_BOOSTED) {
|
||||
t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED;
|
||||
rt_mutex_unlock(t->rcu_boost_mutex);
|
||||
t->rcu_boost_mutex = NULL;
|
||||
}
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
/*
|
||||
* If this was the last task on the expedited lists,
|
||||
* then we need to report up the rcu_node hierarchy.
|
||||
|
|
@ -391,7 +409,7 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
|
|||
unsigned long flags;
|
||||
struct task_struct *t;
|
||||
|
||||
if (!rcu_preempted_readers(rnp))
|
||||
if (!rcu_preempt_blocked_readers_cgp(rnp))
|
||||
return;
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
t = list_entry(rnp->gp_tasks,
|
||||
|
|
@ -430,7 +448,7 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
|
|||
{
|
||||
struct task_struct *t;
|
||||
|
||||
if (!rcu_preempted_readers(rnp))
|
||||
if (!rcu_preempt_blocked_readers_cgp(rnp))
|
||||
return;
|
||||
t = list_entry(rnp->gp_tasks,
|
||||
struct task_struct, rcu_node_entry);
|
||||
|
|
@ -460,7 +478,7 @@ static void rcu_preempt_stall_reset(void)
|
|||
*/
|
||||
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
|
||||
{
|
||||
WARN_ON_ONCE(rcu_preempted_readers(rnp));
|
||||
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
|
||||
if (!list_empty(&rnp->blkd_tasks))
|
||||
rnp->gp_tasks = rnp->blkd_tasks.next;
|
||||
WARN_ON_ONCE(rnp->qsmask);
|
||||
|
|
@ -509,7 +527,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
|
|||
* absolutely necessary, but this is a good performance/complexity
|
||||
* tradeoff.
|
||||
*/
|
||||
if (rcu_preempted_readers(rnp))
|
||||
if (rcu_preempt_blocked_readers_cgp(rnp))
|
||||
retval |= RCU_OFL_TASKS_NORM_GP;
|
||||
if (rcu_preempted_readers_exp(rnp))
|
||||
retval |= RCU_OFL_TASKS_EXP_GP;
|
||||
|
|
@ -525,8 +543,22 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
|
|||
rnp_root->gp_tasks = rnp->gp_tasks;
|
||||
if (&t->rcu_node_entry == rnp->exp_tasks)
|
||||
rnp_root->exp_tasks = rnp->exp_tasks;
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
if (&t->rcu_node_entry == rnp->boost_tasks)
|
||||
rnp_root->boost_tasks = rnp->boost_tasks;
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
|
||||
}
|
||||
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
/* In case root is being boosted and leaf is not. */
|
||||
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;
|
||||
raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
|
||||
#endif /* #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
rnp->gp_tasks = NULL;
|
||||
rnp->exp_tasks = NULL;
|
||||
return retval;
|
||||
|
|
@ -684,6 +716,7 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
|
|||
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
||||
if (!list_empty(&rnp->blkd_tasks)) {
|
||||
rnp->exp_tasks = rnp->blkd_tasks.next;
|
||||
rcu_initiate_boost(rnp);
|
||||
must_wait = 1;
|
||||
}
|
||||
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
||||
|
|
@ -830,6 +863,8 @@ void exit_rcu(void)
|
|||
|
||||
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
static struct rcu_state *rcu_state = &rcu_sched_state;
|
||||
|
||||
/*
|
||||
* Tell them what RCU they are running.
|
||||
*/
|
||||
|
|
@ -870,7 +905,7 @@ static void rcu_preempt_note_context_switch(int cpu)
|
|||
* Because preemptable RCU does not exist, there are never any preempted
|
||||
* RCU readers.
|
||||
*/
|
||||
static int rcu_preempted_readers(struct rcu_node *rnp)
|
||||
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -1034,6 +1069,263 @@ static void __init __rcu_init_preempt(void)
|
|||
|
||||
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
|
||||
|
||||
#ifdef CONFIG_RCU_BOOST
|
||||
|
||||
#include "rtmutex_common.h"
|
||||
|
||||
/*
|
||||
* Carry out RCU priority boosting on the task indicated by ->exp_tasks
|
||||
* or ->boost_tasks, advancing the pointer to the next task in the
|
||||
* ->blkd_tasks list.
|
||||
*
|
||||
* Note that irqs must be enabled: boosting the task can block.
|
||||
* Returns 1 if there are more tasks needing to be boosted.
|
||||
*/
|
||||
static int rcu_boost(struct rcu_node *rnp)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rt_mutex mtx;
|
||||
struct task_struct *t;
|
||||
struct list_head *tb;
|
||||
|
||||
if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
|
||||
return 0; /* Nothing left to boost. */
|
||||
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
|
||||
/*
|
||||
* Recheck under the lock: all tasks in need of boosting
|
||||
* might exit their RCU read-side critical sections on their own.
|
||||
*/
|
||||
if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) {
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Preferentially boost tasks blocking expedited grace periods.
|
||||
* This cannot starve the normal grace periods because a second
|
||||
* expedited grace period must boost all blocked tasks, including
|
||||
* those blocking the pre-existing normal grace period.
|
||||
*/
|
||||
if (rnp->exp_tasks != NULL)
|
||||
tb = rnp->exp_tasks;
|
||||
else
|
||||
tb = rnp->boost_tasks;
|
||||
|
||||
/*
|
||||
* We boost task t by manufacturing an rt_mutex that appears to
|
||||
* be held by task t. We leave a pointer to that rt_mutex where
|
||||
* task t can find it, and task t will release the mutex when it
|
||||
* exits its outermost RCU read-side critical section. Then
|
||||
* simply acquiring this artificial rt_mutex will boost task
|
||||
* t's priority. (Thanks to tglx for suggesting this approach!)
|
||||
*
|
||||
* Note that task t must acquire rnp->lock to remove itself from
|
||||
* the ->blkd_tasks list, which it will do from exit() if from
|
||||
* nowhere else. We therefore are guaranteed that task t will
|
||||
* stay around at least until we drop rnp->lock. Note that
|
||||
* rnp->lock also resolves races between our priority boosting
|
||||
* and task t's exiting its outermost RCU read-side critical
|
||||
* section.
|
||||
*/
|
||||
t = container_of(tb, struct task_struct, rcu_node_entry);
|
||||
rt_mutex_init_proxy_locked(&mtx, t);
|
||||
t->rcu_boost_mutex = &mtx;
|
||||
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED;
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */
|
||||
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */
|
||||
|
||||
return rnp->exp_tasks != NULL || 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)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_node *rnp = (struct rcu_node *)arg;
|
||||
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
invoke_rcu_node_kthread(rnp);
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* Priority-boosting kthread. One per leaf rcu_node and one for the
|
||||
* root rcu_node.
|
||||
*/
|
||||
static int rcu_boost_kthread(void *arg)
|
||||
{
|
||||
struct rcu_node *rnp = (struct rcu_node *)arg;
|
||||
int spincnt = 0;
|
||||
int more2boost;
|
||||
|
||||
for (;;) {
|
||||
wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks ||
|
||||
rnp->exp_tasks ||
|
||||
kthread_should_stop());
|
||||
if (kthread_should_stop())
|
||||
break;
|
||||
more2boost = rcu_boost(rnp);
|
||||
if (more2boost)
|
||||
spincnt++;
|
||||
else
|
||||
spincnt = 0;
|
||||
if (spincnt > 10) {
|
||||
rcu_yield(rcu_boost_kthread_timer, (unsigned long)rnp);
|
||||
spincnt = 0;
|
||||
}
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Check to see if it is time to start boosting RCU readers that are
|
||||
* blocking the current grace period, and, if so, tell the per-rcu_node
|
||||
* 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.
|
||||
*/
|
||||
static void rcu_initiate_boost(struct rcu_node *rnp)
|
||||
{
|
||||
struct task_struct *t;
|
||||
|
||||
if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL)
|
||||
return;
|
||||
if (rnp->exp_tasks != NULL ||
|
||||
(rnp->gp_tasks != NULL &&
|
||||
rnp->boost_tasks == NULL &&
|
||||
rnp->qsmask == 0 &&
|
||||
ULONG_CMP_GE(jiffies, rnp->boost_time))) {
|
||||
if (rnp->exp_tasks == NULL)
|
||||
rnp->boost_tasks = rnp->gp_tasks;
|
||||
t = rnp->boost_kthread_task;
|
||||
if (t != NULL)
|
||||
wake_up_process(t);
|
||||
}
|
||||
}
|
||||
|
||||
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
|
||||
cpumask_var_t cm)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct task_struct *t;
|
||||
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
t = rnp->boost_kthread_task;
|
||||
if (t != NULL)
|
||||
set_cpus_allowed_ptr(rnp->boost_kthread_task, cm);
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
}
|
||||
|
||||
#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
|
||||
|
||||
/*
|
||||
* Do priority-boost accounting for the start of a new grace period.
|
||||
*/
|
||||
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
|
||||
{
|
||||
rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES;
|
||||
}
|
||||
|
||||
/*
|
||||
* Initialize the RCU-boost waitqueue.
|
||||
*/
|
||||
static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp)
|
||||
{
|
||||
init_waitqueue_head(&rnp->boost_wq);
|
||||
}
|
||||
|
||||
/*
|
||||
* Create an RCU-boost kthread for the specified node if one does not
|
||||
* already exist. We only create this kthread for preemptible RCU.
|
||||
* 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)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct sched_param sp;
|
||||
struct task_struct *t;
|
||||
|
||||
if (&rcu_preempt_state != rsp)
|
||||
return 0;
|
||||
if (rnp->boost_kthread_task != NULL)
|
||||
return 0;
|
||||
t = kthread_create(rcu_boost_kthread, (void *)rnp,
|
||||
"rcub%d", rnp_index);
|
||||
if (IS_ERR(t))
|
||||
return PTR_ERR(t);
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
rnp->boost_kthread_task = t;
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
wake_up_process(t);
|
||||
sp.sched_priority = RCU_KTHREAD_PRIO;
|
||||
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
||||
return 0;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
|
||||
static void rcu_stop_boost_kthread(struct rcu_node *rnp)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct task_struct *t;
|
||||
|
||||
raw_spin_lock_irqsave(&rnp->lock, flags);
|
||||
t = rnp->boost_kthread_task;
|
||||
rnp->boost_kthread_task = NULL;
|
||||
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
||||
if (t != NULL)
|
||||
kthread_stop(t);
|
||||
}
|
||||
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
#else /* #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
static void rcu_initiate_boost(struct rcu_node *rnp)
|
||||
{
|
||||
}
|
||||
|
||||
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
|
||||
cpumask_var_t cm)
|
||||
{
|
||||
}
|
||||
|
||||
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
|
||||
{
|
||||
}
|
||||
|
||||
static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp)
|
||||
{
|
||||
}
|
||||
|
||||
static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
|
||||
struct rcu_node *rnp,
|
||||
int rnp_index)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
|
||||
static void rcu_stop_boost_kthread(struct rcu_node *rnp)
|
||||
{
|
||||
}
|
||||
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
#endif /* #else #ifdef CONFIG_RCU_BOOST */
|
||||
|
||||
#ifndef CONFIG_SMP
|
||||
|
||||
void synchronize_sched_expedited(void)
|
||||
|
|
@ -1206,8 +1498,8 @@ static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
|
|||
*
|
||||
* Because it is not legal to invoke rcu_process_callbacks() with irqs
|
||||
* disabled, we do one pass of force_quiescent_state(), then do a
|
||||
* invoke_rcu_kthread() to cause rcu_process_callbacks() to be invoked later.
|
||||
* The per-cpu rcu_dyntick_drain variable controls the sequencing.
|
||||
* invoke_rcu_cpu_kthread() to cause rcu_process_callbacks() to be invoked
|
||||
* later. The per-cpu rcu_dyntick_drain variable controls the sequencing.
|
||||
*/
|
||||
int rcu_needs_cpu(int cpu)
|
||||
{
|
||||
|
|
@ -1257,7 +1549,7 @@ int rcu_needs_cpu(int cpu)
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/* If RCU callbacks are still pending, RCU still needs this CPU. */
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if (c)
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invoke_rcu_kthread();
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invoke_rcu_cpu_kthread();
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return c;
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}
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