return rcu_seq_done(&rsp->expedited_sequence, s);
}
+/*
+ * Reset the ->expmaskinit values in the rcu_node tree to reflect any
+ * recent CPU-online activity. Note that these masks are not cleared
+ * when CPUs go offline, so they reflect the union of all CPUs that have
+ * ever been online. This means that this function normally takes its
+ * no-work-to-do fastpath.
+ */
+static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
+{
+ bool done;
+ unsigned long flags;
+ unsigned long mask;
+ unsigned long oldmask;
+ int ncpus = READ_ONCE(rsp->ncpus);
+ struct rcu_node *rnp;
+ struct rcu_node *rnp_up;
+
+ /* If no new CPUs onlined since last time, nothing to do. */
+ if (likely(ncpus == rsp->ncpus_snap))
+ return;
+ rsp->ncpus_snap = ncpus;
+
+ /*
+ * Each pass through the following loop propagates newly onlined
+ * CPUs for the current rcu_node structure up the rcu_node tree.
+ */
+ rcu_for_each_leaf_node(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ if (rnp->expmaskinit == rnp->expmaskinitnext) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ continue; /* No new CPUs, nothing to do. */
+ }
+
+ /* Update this node's mask, track old value for propagation. */
+ oldmask = rnp->expmaskinit;
+ rnp->expmaskinit = rnp->expmaskinitnext;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+ /* If was already nonzero, nothing to propagate. */
+ if (oldmask)
+ continue;
+
+ /* Propagate the new CPU up the tree. */
+ mask = rnp->grpmask;
+ rnp_up = rnp->parent;
+ done = false;
+ while (rnp_up) {
+ raw_spin_lock_irqsave(&rnp_up->lock, flags);
+ smp_mb__after_unlock_lock();
+ if (rnp_up->expmaskinit)
+ done = true;
+ rnp_up->expmaskinit |= mask;
+ raw_spin_unlock_irqrestore(&rnp_up->lock, flags);
+ if (done)
+ break;
+ mask = rnp_up->grpmask;
+ rnp_up = rnp_up->parent;
+ }
+ }
+}
+
+/*
+ * Reset the ->expmask values in the rcu_node tree in preparation for
+ * a new expedited grace period.
+ */
+static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
+{
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ sync_exp_reset_tree_hotplug(rsp);
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ WARN_ON_ONCE(rnp->expmask);
+ rnp->expmask = rnp->expmaskinit;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ }
+}
+
/*
* Return non-zero if there are any tasks in RCU read-side critical
* sections blocking the current preemptible-RCU expedited grace period.
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
- rdp->beenonline = 1; /* We have now been online. */
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->blimit = blimit;
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock();
rnp->qsmaskinitnext |= mask;
+ rnp->expmaskinitnext |= mask;
+ if (!rdp->beenonline)
+ WRITE_ONCE(rsp->ncpus, READ_ONCE(rsp->ncpus) + 1);
+ rdp->beenonline = true; /* We have now been online. */
rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
rdp->completed = rnp->completed;
rdp->passed_quiesce = false;
/* an rcu_data structure, otherwise, each */
/* bit corresponds to a child rcu_node */
/* structure. */
- unsigned long expmask; /* Groups that have ->blkd_tasks */
- /* elements that need to drain to allow the */
- /* current expedited grace period to */
- /* complete (only for PREEMPT_RCU). */
unsigned long qsmaskinit;
- /* Per-GP initial value for qsmask & expmask. */
+ /* Per-GP initial value for qsmask. */
/* Initialized from ->qsmaskinitnext at the */
/* beginning of each grace period. */
unsigned long qsmaskinitnext;
/* Online CPUs for next grace period. */
+ unsigned long expmask; /* CPUs or groups that need to check in */
+ /* to allow the current expedited GP */
+ /* to complete. */
+ unsigned long expmaskinit;
+ /* Per-GP initial values for expmask. */
+ /* Initialized from ->expmaskinitnext at the */
+ /* beginning of each expedited GP. */
+ unsigned long expmaskinitnext;
+ /* Online CPUs for next expedited GP. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
void (*call)(struct rcu_head *head, /* call_rcu() flavor. */
void (*func)(struct rcu_head *head));
+ int ncpus; /* # CPUs seen so far. */
/* The following fields are guarded by the root rcu_node's lock. */
atomic_long_t expedited_normal; /* # fallbacks to normal. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
wait_queue_head_t expedited_wq; /* Wait for check-ins. */
+ int ncpus_snap; /* # CPUs seen last time. */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
EXPORT_SYMBOL_GPL(synchronize_rcu);
/*
- * Snapshot the tasks blocking the newly started preemptible-RCU expedited
- * grace period for the specified rcu_node structure, phase 1. If there
- * are such tasks, set the ->expmask bits up the rcu_node tree and also
- * set the ->expmask bits on the leaf rcu_node structures to tell phase 2
- * that work is needed here.
- *
- * Caller must hold the root rcu_node's exp_funnel_mutex.
+ * Select the nodes that the upcoming expedited grace period needs
+ * to wait for.
*/
-static void
-sync_rcu_preempt_exp_init1(struct rcu_state *rsp, struct rcu_node *rnp)
+static void sync_rcu_exp_select_nodes(struct rcu_state *rsp)
{
unsigned long flags;
- unsigned long mask;
- struct rcu_node *rnp_up;
+ struct rcu_node *rnp;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- smp_mb__after_unlock_lock();
- WARN_ON_ONCE(rnp->expmask);
- WARN_ON_ONCE(rnp->exp_tasks);
- if (!rcu_preempt_has_tasks(rnp)) {
- /* No blocked tasks, nothing to do. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- /* Call for Phase 2 and propagate ->expmask bits up the tree. */
- rnp->expmask = 1;
- rnp_up = rnp;
- while (rnp_up->parent) {
- mask = rnp_up->grpmask;
- rnp_up = rnp_up->parent;
- if (rnp_up->expmask & mask)
- break;
- raw_spin_lock(&rnp_up->lock); /* irqs already off */
+ sync_exp_reset_tree(rsp);
+ rcu_for_each_leaf_node(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
- rnp_up->expmask |= mask;
- raw_spin_unlock(&rnp_up->lock); /* irqs still off */
- }
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Snapshot the tasks blocking the newly started preemptible-RCU expedited
- * grace period for the specified rcu_node structure, phase 2. If the
- * leaf rcu_node structure has its ->expmask field set, check for tasks.
- * If there are some, clear ->expmask and set ->exp_tasks accordingly,
- * then initiate RCU priority boosting. Otherwise, clear ->expmask and
- * invoke rcu_report_exp_rnp() to clear out the upper-level ->expmask bits,
- * enabling rcu_read_unlock_special() to do the bit-clearing.
- *
- * Caller must hold the root rcu_node's exp_funnel_mutex.
- */
-static void
-sync_rcu_preempt_exp_init2(struct rcu_state *rsp, struct rcu_node *rnp)
-{
- unsigned long flags;
-
- raw_spin_lock_irqsave(&rnp->lock, flags);
- smp_mb__after_unlock_lock();
- if (!rnp->expmask) {
- /* Phase 1 didn't do anything, so Phase 2 doesn't either. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
-
- /* Phase 1 is over. */
- rnp->expmask = 0;
-
- /*
- * If there are still blocked tasks, set up ->exp_tasks so that
- * rcu_read_unlock_special() will wake us and then boost them.
- */
- if (rcu_preempt_has_tasks(rnp)) {
- rnp->exp_tasks = rnp->blkd_tasks.next;
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
- return;
+ rnp->expmask = 0; /* No per-CPU component yet. */
+ if (!rcu_preempt_has_tasks(rnp)) {
+ /* FIXME: Want __rcu_report_exp_rnp() here. */
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ } else {
+ rnp->exp_tasks = rnp->blkd_tasks.next;
+ rcu_initiate_boost(rnp, flags);
+ }
+ rcu_report_exp_rnp(rsp, rnp, false);
}
-
- /* No longer any blocked tasks, so undo bit setting. */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- rcu_report_exp_rnp(rsp, rnp, false);
}
/**
/* force all RCU readers onto ->blkd_tasks lists. */
synchronize_sched_expedited();
- /*
- * Snapshot current state of ->blkd_tasks lists into ->expmask.
- * Phase 1 sets bits and phase 2 permits rcu_read_unlock_special()
- * to start clearing them. Doing this in one phase leads to
- * strange races between setting and clearing bits, so just say "no"!
- */
- rcu_for_each_leaf_node(rsp, rnp)
- sync_rcu_preempt_exp_init1(rsp, rnp);
- rcu_for_each_leaf_node(rsp, rnp)
- sync_rcu_preempt_exp_init2(rsp, rnp);
+ /* Initialize the rcu_node tree in preparation for the wait. */
+ sync_rcu_exp_select_nodes(rsp);
/* Wait for snapshotted ->blkd_tasks lists to drain. */
rnp = rcu_get_root(rsp);
projects / karo-tx-linux.git / commitdiff