static struct rcu_state *rcu_state_p = &rcu_preempt_state;
static int rcu_preempted_readers_exp(struct rcu_node *rnp);
+static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
+ bool wake);
/*
* Tell them what RCU they are running.
return np;
}
+/*
+ * Return true if the specified rcu_node structure has tasks that were
+ * preempted within an RCU read-side critical section.
+ */
+static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
+{
+ return !list_empty(&rnp->blkd_tasks);
+}
+
/*
* Handle special cases during rcu_read_unlock(), such as needing to
* notify RCU core processing or task having blocked during the RCU
*/
void rcu_read_unlock_special(struct task_struct *t)
{
- int empty;
- int empty_exp;
- int empty_exp_now;
+ bool empty;
+ bool empty_exp;
+ bool empty_norm;
+ bool empty_exp_now;
unsigned long flags;
struct list_head *np;
#ifdef CONFIG_RCU_BOOST
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
- empty = !rcu_preempt_blocked_readers_cgp(rnp);
+ empty = !rcu_preempt_has_tasks(rnp);
+ empty_norm = !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);
drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;
#endif /* #ifdef CONFIG_RCU_BOOST */
+ /*
+ * If this was the last task on the list, go see if we
+ * need to propagate ->qsmaskinit bit clearing up the
+ * rcu_node tree.
+ */
+ if (!empty && !rcu_preempt_has_tasks(rnp))
+ rcu_cleanup_dead_rnp(rnp);
+
/*
* If this was the last task on the current list, and if
* we aren't waiting on any CPUs, report the quiescent state.
* so we must take a snapshot of the expedited state.
*/
empty_exp_now = !rcu_preempted_readers_exp(rnp);
- if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) {
+ if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) {
trace_rcu_quiescent_state_report(TPS("preempt_rcu"),
rnp->gpnum,
0, rnp->qsmask,
#ifdef CONFIG_RCU_BOOST
/* Unboost if we were boosted. */
- if (drop_boost_mutex) {
+ if (drop_boost_mutex)
rt_mutex_unlock(&rnp->boost_mtx);
- complete(&rnp->boost_completion);
- }
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
{
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
- if (!list_empty(&rnp->blkd_tasks))
+ if (rcu_preempt_has_tasks(rnp))
rnp->gp_tasks = rnp->blkd_tasks.next;
WARN_ON_ONCE(rnp->qsmask);
}
#ifdef CONFIG_HOTPLUG_CPU
-/*
- * Handle tasklist migration for case in which all CPUs covered by the
- * specified rcu_node have gone offline. Move them up to the root
- * rcu_node. The reason for not just moving them to the immediate
- * parent is to remove the need for rcu_read_unlock_special() to
- * make more than two attempts to acquire the target rcu_node's lock.
- * Returns true if there were tasks blocking the current RCU grace
- * period.
- *
- * Returns 1 if there was previously a task blocking the current grace
- * period on the specified rcu_node structure.
- *
- * The caller must hold rnp->lock with irqs disabled.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
- struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- struct list_head *lp;
- struct list_head *lp_root;
- int retval = 0;
- struct rcu_node *rnp_root = rcu_get_root(rsp);
- struct task_struct *t;
-
- if (rnp == rnp_root) {
- WARN_ONCE(1, "Last CPU thought to be offlined?");
- return 0; /* Shouldn't happen: at least one CPU online. */
- }
-
- /* If we are on an internal node, complain bitterly. */
- WARN_ON_ONCE(rnp != rdp->mynode);
-
- /*
- * Move tasks up to root rcu_node. Don't try to get fancy for
- * this corner-case operation -- just put this node's tasks
- * at the head of the root node's list, and update the root node's
- * ->gp_tasks and ->exp_tasks pointers to those of this node's,
- * if non-NULL. This might result in waiting for more tasks than
- * absolutely necessary, but this is a good performance/complexity
- * tradeoff.
- */
- if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0)
- retval |= RCU_OFL_TASKS_NORM_GP;
- if (rcu_preempted_readers_exp(rnp))
- retval |= RCU_OFL_TASKS_EXP_GP;
- lp = &rnp->blkd_tasks;
- lp_root = &rnp_root->blkd_tasks;
- while (!list_empty(lp)) {
- t = list_entry(lp->next, typeof(*t), rcu_node_entry);
- raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
- smp_mb__after_unlock_lock();
- list_del(&t->rcu_node_entry);
- t->rcu_blocked_node = rnp_root;
- list_add(&t->rcu_node_entry, lp_root);
- if (&t->rcu_node_entry == rnp->gp_tasks)
- 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 */
- }
-
- rnp->gp_tasks = NULL;
- rnp->exp_tasks = NULL;
-#ifdef CONFIG_RCU_BOOST
- 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 */
- smp_mb__after_unlock_lock();
- if (rnp_root->boost_tasks != NULL &&
- 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 */
-
- return retval;
-}
-
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
- if (list_empty(&rnp->blkd_tasks)) {
+ if (!rcu_preempt_has_tasks(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else {
rnp->exp_tasks = rnp->blkd_tasks.next;
#ifdef CONFIG_HOTPLUG_CPU
-/* Because preemptible RCU does not exist, no quieting of tasks. */
-static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
- __releases(rnp->lock)
+/*
+ * Because there is no preemptible RCU, there can be no readers blocked.
+ */
+static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
{
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ return false;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
WARN_ON_ONCE(rnp->qsmask);
}
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible RCU does not exist, it never needs to migrate
- * tasks that were blocked within RCU read-side critical sections, and
- * such non-existent tasks cannot possibly have been blocking the current
- * grace period.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
- struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- return 0;
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Because preemptible RCU does not exist, it never has any callbacks
* to check.
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible RCU does not exist, there is never any need to
- * report on tasks preempted in RCU read-side critical sections during
- * expedited RCU grace periods.
- */
-static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
- bool wake)
-{
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Because preemptible RCU does not exist, rcu_barrier() is just
* another name for rcu_barrier_sched().
static void rcu_initiate_boost_trace(struct rcu_node *rnp)
{
- if (list_empty(&rnp->blkd_tasks))
+ if (!rcu_preempt_has_tasks(rnp))
rnp->n_balk_blkd_tasks++;
else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL)
rnp->n_balk_exp_gp_tasks++;
struct task_struct *t;
struct list_head *tb;
- if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
+ if (ACCESS_ONCE(rnp->exp_tasks) == NULL &&
+ ACCESS_ONCE(rnp->boost_tasks) == NULL)
return 0; /* Nothing left to boost. */
raw_spin_lock_irqsave(&rnp->lock, flags);
*/
t = container_of(tb, struct task_struct, rcu_node_entry);
rt_mutex_init_proxy_locked(&rnp->boost_mtx, t);
- init_completion(&rnp->boost_completion);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/* Lock only for side effect: boosts task t's priority. */
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
- /* Wait for boostee to be done w/boost_mtx before reinitializing. */
- wait_for_completion(&rnp->boost_completion);
-
return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
ACCESS_ONCE(rnp->boost_tasks) != NULL;
}
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
if ((mask & 0x1) && cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm);
- if (cpumask_weight(cm) == 0) {
+ if (cpumask_weight(cm) == 0)
cpumask_setall(cm);
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
- cpumask_clear_cpu(cpu, cm);
- WARN_ON_ONCE(cpumask_weight(cm) == 0);
- }
set_cpus_allowed_ptr(t, cm);
free_cpumask_var(cm);
}
for_each_possible_cpu(cpu)
per_cpu(rcu_cpu_has_work, cpu) = 0;
BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
- rnp = rcu_get_root(rcu_state_p);
- (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
- if (NUM_RCU_NODES > 1) {
- rcu_for_each_leaf_node(rcu_state_p, rnp)
- (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
- }
+ rcu_for_each_leaf_node(rcu_state_p, rnp)
+ (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
}
static void rcu_prepare_kthreads(int cpu)
projects / mirror_ubuntu-jammy-kernel.git / blobdiff