rcu: Abstract rcu_start_future_gp() from rcu_nocb_wait_gp()
CPUs going idle will need to record the need for a future grace
period, but won't actually need to block waiting on it. This commit
therefore splits rcu_start_future_gp(), which does the recording, from
rcu_nocb_wait_gp(), which now invokes rcu_start_future_gp() to do the
recording, after which rcu_nocb_wait_gp() does the waiting.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f3f0020..723af5f 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2022,22 +2022,12 @@
}
/*
- * Clean up this rcu_node structure's no-CBs state at the end of
- * a grace period, and also return whether any no-CBs CPU associated
- * with this rcu_node structure needs another grace period.
+ * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
+ * grace period.
*/
-static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
{
- int c = rnp->completed;
- int needmore;
-
- wake_up_all(&rnp->nocb_gp_wq[c & 0x1]);
- rnp->need_future_gp[c & 0x1] = 0;
- needmore = rnp->need_future_gp[(c + 1) & 0x1];
- trace_rcu_future_grace_period(rsp->name, rnp->gpnum, rnp->completed,
- c, rnp->level, rnp->grplo, rnp->grphi,
- needmore ? "CleanupMore" : "Cleanup");
- return needmore;
+ wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]);
}
/*
@@ -2175,84 +2165,16 @@
bool d;
unsigned long flags;
struct rcu_node *rnp = rdp->mynode;
- struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
- c = rnp->completed + 2;
-
- /* Count our request for a grace period. */
- rnp->need_future_gp[c & 0x1]++;
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
- rnp->completed, c, rnp->level,
- rnp->grplo, rnp->grphi, "Startleaf");
-
- if (rnp->gpnum != rnp->completed) {
-
- /*
- * This rcu_node structure believes that a grace period
- * is in progress, so we are done. When this grace
- * period ends, our request will be acted upon.
- */
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
- rnp->completed, c, rnp->level,
- rnp->grplo, rnp->grphi,
- "Startedleaf");
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
- } else {
-
- /*
- * Might not be a grace period, check root rcu_node
- * structure to see if we must start one.
- */
- if (rnp != rnp_root)
- raw_spin_lock(&rnp_root->lock); /* irqs disabled. */
- if (rnp_root->gpnum != rnp_root->completed) {
- trace_rcu_future_grace_period(rdp->rsp->name,
- rnp->gpnum,
- rnp->completed,
- c, rnp->level,
- rnp->grplo, rnp->grphi,
- "Startedleafroot");
- raw_spin_unlock(&rnp_root->lock); /* irqs disabled. */
- } else {
-
- /*
- * No grace period, so we need to start one.
- * The good news is that we can wait for exactly
- * one grace period instead of part of the current
- * grace period and all of the next grace period.
- * Adjust counters accordingly and start the
- * needed grace period.
- */
- rnp->need_future_gp[c & 0x1]--;
- c = rnp_root->completed + 1;
- rnp->need_future_gp[c & 0x1]++;
- rnp_root->need_future_gp[c & 0x1]++;
- trace_rcu_future_grace_period(rdp->rsp->name,
- rnp->gpnum,
- rnp->completed,
- c, rnp->level,
- rnp->grplo, rnp->grphi,
- "Startedroot");
- rcu_start_gp(rdp->rsp);
- raw_spin_unlock(&rnp->lock);
- }
-
- /* Clean up locking and irq state. */
- if (rnp != rnp_root)
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- else
- local_irq_restore(flags);
- }
+ c = rcu_start_future_gp(rnp, rdp);
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
/*
* Wait for the grace period. Do so interruptibly to avoid messing
* up the load average.
*/
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
- rnp->completed, c, rnp->level,
- rnp->grplo, rnp->grphi, "StartWait");
+ trace_rcu_future_gp(rnp, rdp, c, "StartWait");
for (;;) {
wait_event_interruptible(
rnp->nocb_gp_wq[c & 0x1],
@@ -2260,14 +2182,9 @@
if (likely(d))
break;
flush_signals(current);
- trace_rcu_future_grace_period(rdp->rsp->name,
- rnp->gpnum, rnp->completed, c,
- rnp->level, rnp->grplo,
- rnp->grphi, "ResumeWait");
+ trace_rcu_future_gp(rnp, rdp, c, "ResumeWait");
}
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
- rnp->completed, c, rnp->level,
- rnp->grplo, rnp->grphi, "EndWait");
+ trace_rcu_future_gp(rnp, rdp, c, "EndWait");
smp_mb(); /* Ensure that CB invocation happens after GP end. */
}
@@ -2375,9 +2292,8 @@
return 0;
}
-static int rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
{
- return 0;
}
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
