#include "../locking/rtmutex_common.h"
-/* rcuc/rcub kthread realtime priority */
-static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
-module_param(kthread_prio, int, 0644);
-
/*
* Control variables for per-CPU and per-rcu_node kthreads. These
* handle all flavors of RCU.
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.
rcu_bootup_announce_oddness();
}
-/*
- * Return the number of RCU-preempt batches processed thus far
- * for debug and statistics.
- */
-static long rcu_batches_completed_preempt(void)
-{
- return rcu_preempt_state.completed;
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
-
-/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
- return rcu_batches_completed_preempt();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
/*
* Record a preemptible-RCU quiescent state for the specified CPU. Note
* that this just means that the task currently running on the CPU is
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;
rcu_bootup_announce_oddness();
}
-/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
- return rcu_batches_completed_sched();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
/*
* Because preemptible RCU does not exist, we never have to check for
* CPUs being in quiescent states.
#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)
* completed since we last checked and there are
* callbacks not yet ready to invoke.
*/
- if (rdp->completed != rnp->completed &&
+ if ((rdp->completed != rnp->completed ||
+ unlikely(ACCESS_ONCE(rdp->gpwrap))) &&
rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
note_gp_changes(rsp, rdp);
ticks_value = rsp->gpnum - rdp->gpnum;
}
print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
- pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n",
+ pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n",
cpu, ticks_value, ticks_title,
atomic_read(&rdtp->dynticks) & 0xfff,
rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
+ ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
fast_no_hz);
}
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
{
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+ unsigned long ret;
+#ifdef CONFIG_PROVE_RCU
struct rcu_head *rhp;
+#endif /* #ifdef CONFIG_PROVE_RCU */
- /* No-CBs CPUs might have callbacks on any of three lists. */
+ /*
+ * Check count of all no-CBs callbacks awaiting invocation.
+ * There needs to be a barrier before this function is called,
+ * but associated with a prior determination that no more
+ * callbacks would be posted. In the worst case, the first
+ * barrier in _rcu_barrier() suffices (but the caller cannot
+ * necessarily rely on this, not a substitute for the caller
+ * getting the concurrency design right!). There must also be
+ * a barrier between the following load an posting of a callback
+ * (if a callback is in fact needed). This is associated with an
+ * atomic_inc() in the caller.
+ */
+ ret = atomic_long_read(&rdp->nocb_q_count);
+
+#ifdef CONFIG_PROVE_RCU
rhp = ACCESS_ONCE(rdp->nocb_head);
if (!rhp)
rhp = ACCESS_ONCE(rdp->nocb_gp_head);
cpu, rhp->func);
WARN_ON_ONCE(1);
}
+#endif /* #ifdef CONFIG_PROVE_RCU */
- return !!rhp;
+ return !!ret;
}
/*
struct task_struct *t;
/* Enqueue the callback on the nocb list and update counts. */
+ atomic_long_add(rhcount, &rdp->nocb_q_count);
+ /* rcu_barrier() relies on ->nocb_q_count add before xchg. */
old_rhpp = xchg(&rdp->nocb_tail, rhtp);
ACCESS_ONCE(*old_rhpp) = rhp;
- atomic_long_add(rhcount, &rdp->nocb_q_count);
atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy);
smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */
/* Move callbacks to wait-for-GP list, which is empty. */
ACCESS_ONCE(rdp->nocb_head) = NULL;
rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head);
- rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0);
- rdp->nocb_gp_count_lazy =
- atomic_long_xchg(&rdp->nocb_q_count_lazy, 0);
gotcbs = true;
}
/* Append callbacks to follower's "done" list. */
tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail);
*tail = rdp->nocb_gp_head;
- atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count);
- atomic_long_add(rdp->nocb_gp_count_lazy,
- &rdp->nocb_follower_count_lazy);
smp_mb__after_atomic(); /* Store *tail before wakeup. */
if (rdp != my_rdp && tail == &rdp->nocb_follower_head) {
/*
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty");
ACCESS_ONCE(rdp->nocb_follower_head) = NULL;
tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head);
- c = atomic_long_xchg(&rdp->nocb_follower_count, 0);
- cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0);
- rdp->nocb_p_count += c;
- rdp->nocb_p_count_lazy += cl;
/* Each pass through the following loop invokes a callback. */
- trace_rcu_batch_start(rdp->rsp->name, cl, c, -1);
+ trace_rcu_batch_start(rdp->rsp->name,
+ atomic_long_read(&rdp->nocb_q_count_lazy),
+ atomic_long_read(&rdp->nocb_q_count), -1);
c = cl = 0;
while (list) {
next = list->next;
list = next;
}
trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
- ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c;
- ACCESS_ONCE(rdp->nocb_p_count_lazy) =
- rdp->nocb_p_count_lazy - cl;
+ smp_mb__before_atomic(); /* _add after CB invocation. */
+ atomic_long_add(-c, &rdp->nocb_q_count);
+ atomic_long_add(-cl, &rdp->nocb_q_count_lazy);
rdp->n_nocbs_invoked += c;
}
return 0;
projects / linux-drm-fsl-dcu.git / blobdiff