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rcu: Consolidate tree setup for synchronize_rcu_expedited()

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This commit replaces sync_rcu_preempt_exp_init1(() and
sync_rcu_preempt_exp_init2() with sync_exp_reset_tree_hotplug()
and sync_exp_reset_tree(), which will also be used by
synchronize_sched_expedited(), and sync_rcu_exp_select_nodes(), which
contains code specific to synchronize_rcu_expedited().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2015-07-31 16:04:45 -07:00
parent 7922cd0e56
commit b9585e940a
3 changed files with 115 additions and 90 deletions
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86
kernel/rcu/tree.c
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@@ -3379,6 +3379,87 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
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.
@@ -3971,7 +4052,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
/* 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;
@@ -3993,6 +4073,10 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
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;