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Subject[PATCH tip/core/rcu 1/3] rcu: Open-code the rcu_cblist_empty() function
Date
Because the rcu_cblist_empty() just samples the ->head pointer, and
because the rcu_cblist structure is quite straightforward, it makes
sense to open-code rcu_cblist_empty(p) as !p->head, cutting out a
level of indirection. This commit makes this change.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/rcu/rcu_segcblist.h | 8 +-------
kernel/rcu/tree.c | 9 ++++-----
kernel/rcu/tree_plugin.h | 4 ++--
3 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 86bc1101b806..7d18d41f0116 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -22,12 +22,6 @@

#include <linux/rcu_segcblist.h>

-/* Is simple callback list empty? */
-static inline bool rcu_cblist_empty(struct rcu_cblist *rclp)
-{
- return !rclp->head;
-}
-
/* Return number of callbacks in simple callback list. */
static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
{
@@ -66,7 +60,7 @@ static inline struct rcu_head *rcu_cblist_head(struct rcu_cblist *rclp)
*/
static inline struct rcu_head **rcu_cblist_tail(struct rcu_cblist *rclp)
{
- WARN_ON_ONCE(rcu_cblist_empty(rclp));
+ WARN_ON_ONCE(!rclp->head);
return rclp->tail;
}

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 91fff49d5869..35152414760d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2647,9 +2647,9 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)

/* First adopt the ready-to-invoke callbacks, then the done ones. */
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rsp->orphan_done);
- WARN_ON_ONCE(!rcu_cblist_empty(&rsp->orphan_done));
+ WARN_ON_ONCE(rsp->orphan_done.head);
rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rsp->orphan_pend);
- WARN_ON_ONCE(!rcu_cblist_empty(&rsp->orphan_pend));
+ WARN_ON_ONCE(rsp->orphan_pend.head);
WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) !=
!rcu_segcblist_n_cbs(&rdp->cblist));
}
@@ -2800,9 +2800,8 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)

local_irq_save(flags);
count = -rcu_cblist_n_cbs(&rcl);
- trace_rcu_batch_end(rsp->name, count, !rcu_cblist_empty(&rcl),
- need_resched(), is_idle_task(current),
- rcu_is_callbacks_kthread());
+ trace_rcu_batch_end(rsp->name, count, !!rcl.head, need_resched(),
+ is_idle_task(current), rcu_is_callbacks_kthread());

/* Update counts and requeue any remaining callbacks. */
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7f1d677a2a25..6b4b1f8a272d 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1942,12 +1942,12 @@ static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
return false;

/* First, enqueue the donelist, if any. This preserves CB ordering. */
- if (!rcu_cblist_empty(&rsp->orphan_done)) {
+ if (rsp->orphan_done.head) {
__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_done),
rcu_cblist_tail(&rsp->orphan_done),
ql, qll, flags);
}
- if (!rcu_cblist_empty(&rsp->orphan_pend)) {
+ if (rsp->orphan_pend.head) {
__call_rcu_nocb_enqueue(rdp, rcu_cblist_head(&rsp->orphan_pend),
rcu_cblist_tail(&rsp->orphan_pend),
ql, qll, flags);
--
2.5.2
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