From 133df75cec1379ccd1603c56cf44b73e2ea8161f Mon Sep 17 00:00:00 2001
From: Hongze Cheng <hzcheng@taosdata.com>
Date: Thu, 13 May 2021 15:15:30 +0800
Subject: [PATCH] [TD-4170]<hotfix>:improve skiplist rand performance

---
 src/util/inc/tskiplist.h | 1 +
 src/util/src/tskiplist.c | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/util/inc/tskiplist.h b/src/util/inc/tskiplist.h
index 2c4d1a86ef..17f5940b49 100644
--- a/src/util/inc/tskiplist.h
+++ b/src/util/inc/tskiplist.h
@@ -96,6 +96,7 @@ typedef struct tSkipListState {
 } tSkipListState;
 
 typedef struct SSkipList {
+  unsigned int      seed;
   __compar_fn_t     comparFn;
   __sl_key_fn_t     keyFn;
   pthread_rwlock_t *lock;
diff --git a/src/util/src/tskiplist.c b/src/util/src/tskiplist.c
index e3798162e8..1bf6385288 100644
--- a/src/util/src/tskiplist.c
+++ b/src/util/src/tskiplist.c
@@ -50,6 +50,7 @@ SSkipList *tSkipListCreate(uint8_t maxLevel, uint8_t keyType, uint16_t keyLen, _
   pSkipList->len = keyLen;
   pSkipList->flags = flags;
   pSkipList->keyFn = fn;
+  pSkipList->seed = rand();
   if (comparFn == NULL) {
     pSkipList->comparFn = getKeyComparFunc(keyType);
   } else {
@@ -545,7 +546,7 @@ static FORCE_INLINE int32_t getSkipListNodeRandomHeight(SSkipList *pSkipList) {
   const uint32_t factor = 4;
 
   int32_t n = 1;
-  while ((rand() % factor) == 0 && n <= pSkipList->maxLevel) {
+  while ((rand_r(&(pSkipList->seed)) % factor) == 0 && n <= pSkipList->maxLevel) {
     n++;
   }
 
-- 
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