[PATCH tip/core/rcu 1/9] rcu: Eliminate HOTPLUG_CPU #ifdef in favor of IS_ENABLED()

From: Paul E. McKenney
Date: Tue May 12 2015 - 17:51:34 EST


From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

This commit removes a HOTPLUG_CPU #ifdef, replacing it with
IS_ENABLED()-protected return statements. This relies on the
optimizer to remove any resulting dead code.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 39 ++++++++++++++-------------------------
1 file changed, 14 insertions(+), 25 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4d3299577d7b..7c323e320075 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2333,8 +2333,6 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
}

-#ifdef CONFIG_HOTPLUG_CPU
-
/*
* Send the specified CPU's RCU callbacks to the orphanage. The
* specified CPU must be offline, and the caller must hold the
@@ -2345,7 +2343,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
struct rcu_node *rnp, struct rcu_data *rdp)
{
/* No-CBs CPUs do not have orphanable callbacks. */
- if (rcu_is_nocb_cpu(rdp->cpu))
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_is_nocb_cpu(rdp->cpu))
return;

/*
@@ -2404,7 +2402,8 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);

/* No-CBs CPUs are handled specially. */
- if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
+ rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
return;

/* Do the accounting first. */
@@ -2451,6 +2450,9 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
RCU_TRACE(struct rcu_node *rnp = rdp->mynode);

+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ return;
+
RCU_TRACE(mask = rdp->grpmask);
trace_rcu_grace_period(rsp->name,
rnp->gpnum + 1 - !!(rnp->qsmask & mask),
@@ -2479,7 +2481,8 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
long mask;
struct rcu_node *rnp = rnp_leaf;

- if (rnp->qsmaskinit || rcu_preempt_has_tasks(rnp))
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
+ rnp->qsmaskinit || rcu_preempt_has_tasks(rnp))
return;
for (;;) {
mask = rnp->grpmask;
@@ -2510,6 +2513,9 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */

+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ return;
+
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
mask = rdp->grpmask;
raw_spin_lock_irqsave(&rnp->lock, flags);
@@ -2531,6 +2537,9 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */

+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
+ return;
+
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);

@@ -2545,26 +2554,6 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
cpu, rdp->qlen, rdp->nxtlist);
}

-#else /* #ifdef CONFIG_HOTPLUG_CPU */
-
-static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
-{
-}
-
-static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
-{
-}
-
-static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
-{
-}
-
-static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Invoke any RCU callbacks that have made it to the end of their grace
* period. Thottle as specified by rdp->blimit.
--
1.8.1.5

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