*/
static int rcu_scheduler_fully_active __read_mostly;
+static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
+static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
unsigned long rcutorture_testseq;
unsigned long rcutorture_vernum;
+/*
+ * Compute the mask of online CPUs for the specified rcu_node structure.
+ * This will not be stable unless the rcu_node structure's ->lock is
+ * held, but the bit corresponding to the current CPU will be stable
+ * in most contexts.
+ */
+unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
+{
+ return ACCESS_ONCE(rnp->qsmaskinitnext);
+}
+
/*
* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
* permit this function to be invoked without holding the root rcu_node
preempt_disable();
rdp = this_cpu_ptr(&rcu_sched_data);
rnp = rdp->mynode;
- ret = (rdp->grpmask & rnp->qsmaskinit) ||
+ ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) ||
!rcu_scheduler_fully_active;
preempt_enable();
return ret;
*/
static int rcu_gp_init(struct rcu_state *rsp)
{
+ unsigned long oldmask;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
mutex_lock(&rsp->onoff_mutex);
smp_mb__after_unlock_lock(); /* ->gpnum increment before GP! */
+ /*
+ * Apply per-leaf buffered online and offline operations to the
+ * rcu_node tree. Note that this new grace period need not wait
+ * for subsequent online CPUs, and that quiescent-state forcing
+ * will handle subsequent offline CPUs.
+ */
+ rcu_for_each_leaf_node(rsp, rnp) {
+ raw_spin_lock_irq(&rnp->lock);
+ smp_mb__after_unlock_lock();
+ if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
+ !rnp->wait_blkd_tasks) {
+ /* Nothing to do on this leaf rcu_node structure. */
+ raw_spin_unlock_irq(&rnp->lock);
+ continue;
+ }
+
+ /* Record old state, apply changes to ->qsmaskinit field. */
+ oldmask = rnp->qsmaskinit;
+ rnp->qsmaskinit = rnp->qsmaskinitnext;
+
+ /* If zero-ness of ->qsmaskinit changed, propagate up tree. */
+ if (!oldmask != !rnp->qsmaskinit) {
+ if (!oldmask) /* First online CPU for this rcu_node. */
+ rcu_init_new_rnp(rnp);
+ else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */
+ rnp->wait_blkd_tasks = true;
+ else /* Last offline CPU and can propagate. */
+ rcu_cleanup_dead_rnp(rnp);
+ }
+
+ /*
+ * If all waited-on tasks from prior grace period are
+ * done, and if all this rcu_node structure's CPUs are
+ * still offline, propagate up the rcu_node tree and
+ * clear ->wait_blkd_tasks. Otherwise, if one of this
+ * rcu_node structure's CPUs has since come back online,
+ * simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp()
+ * checks for this, so just call it unconditionally).
+ */
+ if (rnp->wait_blkd_tasks &&
+ (!rcu_preempt_has_tasks(rnp) ||
+ rnp->qsmaskinit)) {
+ rnp->wait_blkd_tasks = false;
+ rcu_cleanup_dead_rnp(rnp);
+ }
+
+ raw_spin_unlock_irq(&rnp->lock);
+ }
+
/*
* Set the quiescent-state-needed bits in all the rcu_node
* structures for all currently online CPUs in breadth-first order,
* irqs disabled, and this lock is released upon return, but irqs remain
* disabled.
*/
-static void __maybe_unused rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
+static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock(); /* GP memory ordering. */
rnp->qsmaskinit &= ~mask;
+ rnp->qsmask &= ~mask;
if (rnp->qsmaskinit) {
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
return;
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
+ unsigned long mask;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
+ mask = rdp->grpmask;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */
- rnp->qsmaskinit &= ~rdp->grpmask;
- if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
- rcu_cleanup_dead_rnp(rnp);
- rcu_report_qs_rnp(rdp->grpmask, rsp, rnp, flags); /* Rlses rnp->lock. */
+ rnp->qsmaskinitnext &= ~mask;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
cpu, rdp->qlen, rdp->nxtlist);
}
}
if (mask != 0) {
-
- /* rcu_report_qs_rnp() releases rnp->lock. */
+ /* Idle/offline CPUs, report. */
rcu_report_qs_rnp(mask, rsp, rnp, flags);
- continue;
+ } else if (rnp->parent &&
+ list_empty(&rnp->blkd_tasks) &&
+ !rnp->qsmask &&
+ (rnp->parent->qsmask & rnp->grpmask)) {
+ /*
+ * Race between grace-period initialization and task
+ * existing RCU read-side critical section, report.
+ */
+ rcu_report_unblock_qs_rnp(rsp, rnp, flags);
+ } else {
+ /* Nothing to do here, so just drop the lock. */
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
}
}
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+/*
+ * Propagate ->qsinitmask bits up the rcu_node tree to account for the
+ * first CPU in a given leaf rcu_node structure coming online. The caller
+ * must hold the corresponding leaf rcu_node ->lock with interrrupts
+ * disabled.
+ */
+static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
+{
+ long mask;
+ struct rcu_node *rnp = rnp_leaf;
+
+ for (;;) {
+ mask = rnp->grpmask;
+ rnp = rnp->parent;
+ if (rnp == NULL)
+ return;
+ raw_spin_lock(&rnp->lock); /* Interrupts already disabled. */
+ rnp->qsmaskinit |= mask;
+ raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
+ }
+}
+
/*
* Do boot-time initialization of a CPU's per-CPU RCU data.
*/
(atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- /* Add CPU to rcu_node bitmasks. */
+ /*
+ * Add CPU to leaf rcu_node pending-online bitmask. Any needed
+ * propagation up the rcu_node tree will happen at the beginning
+ * of the next grace period.
+ */
rnp = rdp->mynode;
mask = rdp->grpmask;
- do {
- /* Exclude any attempts to start a new GP on small systems. */
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rnp->qsmaskinit |= mask;
- mask = rnp->grpmask;
- if (rnp == rdp->mynode) {
- /*
- * If there is a grace period in progress, we will
- * set up to wait for it next time we run the
- * RCU core code.
- */
- rdp->gpnum = rnp->completed;
- rdp->completed = rnp->completed;
- rdp->passed_quiesce = 0;
- rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
- rdp->qs_pending = 0;
- trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
- }
- raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
- rnp = rnp->parent;
- } while (rnp != NULL && !(rnp->qsmaskinit & mask));
- local_irq_restore(flags);
+ raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ smp_mb__after_unlock_lock();
+ rnp->qsmaskinitnext |= mask;
+ rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
+ rdp->completed = rnp->completed;
+ rdp->passed_quiesce = false;
+ rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
+ rdp->qs_pending = false;
+ trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
mutex_unlock(&rsp->onoff_mutex);
}
* But first, note that the current CPU must still be
* on line!
*/
- WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0);
+ WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0);
WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) {
list_add(&t->rcu_node_entry, rnp->gp_tasks->prev);
*/
void rcu_read_unlock_special(struct task_struct *t)
{
- bool empty;
bool empty_exp;
bool empty_norm;
bool empty_exp_now;
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
- 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. */
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.
return 0;
}
-#ifdef CONFIG_HOTPLUG_CPU
-
/*
* Because there is no preemptible RCU, there can be no readers blocked.
*/
return false;
}
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Because preemptible RCU does not exist, we never have to check for
* tasks blocked within RCU read-side critical sections.
* Returns zero if all is well, a negated errno otherwise.
*/
static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
- struct rcu_node *rnp)
+ struct rcu_node *rnp)
{
int rnp_index = rnp - &rsp->node[0];
unsigned long flags;
if (&rcu_preempt_state != rsp)
return 0;
- if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
+ if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0)
return 0;
rsp->boost = 1;
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;
+ unsigned long mask = rcu_rnp_online_cpus(rnp);
cpumask_var_t cm;
int cpu;
projects / firefly-linux-kernel-4.4.55.git / commitdiff