From eb9ffb378b9eb3b9f4a0f898e60ade01d3d48283 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Fri, 5 May 2017 20:29:58 +0200
Subject: erts: Add minor lock optimization for lcnt

---
 erts/emulator/beam/erl_lock_count.c | 21 ++++++++++-----------
 erts/emulator/beam/erl_lock_count.h |  1 -
 2 files changed, 10 insertions(+), 12 deletions(-)

(limited to 'erts/emulator/beam')

diff --git a/erts/emulator/beam/erl_lock_count.c b/erts/emulator/beam/erl_lock_count.c
index 49b1f08b44..aee9796171 100644
--- a/erts/emulator/beam/erl_lock_count.c
+++ b/erts/emulator/beam/erl_lock_count.c
@@ -299,22 +299,16 @@ erts_lcnt_lock_list_t *erts_lcnt_list_init(void) {
     return list;
 }
 
-/* only do this on the list with the deleted locks! */
-void erts_lcnt_list_clear(erts_lcnt_lock_list_t *list) {
-    erts_lcnt_lock_t *lock = NULL,
-                     *next = NULL;
+static void lcnt_list_free(erts_lcnt_lock_t *head) {
+    erts_lcnt_lock_t *lock, *next;
 
-    lock = list->head;
+    lock = head;
 
     while(lock != NULL) {
         next = lock->next;
         free(lock);
         lock = next;
     }
-
-    list->head = NULL;
-    list->tail = NULL;
-    list->n    = 0;
 }
 
 void erts_lcnt_list_insert(erts_lcnt_lock_list_t *list, erts_lcnt_lock_t *lock) {
@@ -679,12 +673,17 @@ void erts_lcnt_clear_counters(void) {
         lock->n_stats = 1;
     }
 
-    /* empty deleted locks in lock list */
-    erts_lcnt_list_clear(erts_lcnt_data->deleted_locks);
+    lock = erts_lcnt_data->deleted_locks->head;
+    erts_lcnt_data->deleted_locks->head = NULL;
+    erts_lcnt_data->deleted_locks->tail = NULL;
+    erts_lcnt_data->deleted_locks->n = 0;
 
     lcnt_time(&timer_start);
 
     lcnt_unlock();
+
+    /* free deleted locks */
+    lcnt_list_free(lock);
 }
 
 erts_lcnt_data_t *erts_lcnt_get_data(void) {
diff --git a/erts/emulator/beam/erl_lock_count.h b/erts/emulator/beam/erl_lock_count.h
index be601a26fc..6caffbfe86 100644
--- a/erts/emulator/beam/erl_lock_count.h
+++ b/erts/emulator/beam/erl_lock_count.h
@@ -206,7 +206,6 @@ void erts_lcnt_thread_exit_handler(void);
 /* list operations (local)  */
 erts_lcnt_lock_list_t *erts_lcnt_list_init(void);
 
-void erts_lcnt_list_clear( erts_lcnt_lock_list_t *list);
 void erts_lcnt_list_insert(erts_lcnt_lock_list_t *list, erts_lcnt_lock_t *lock);
 void erts_lcnt_list_delete(erts_lcnt_lock_list_t *list, erts_lcnt_lock_t *lock);
 
-- 
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