From c63552eab1a13c6c05e18d763c7acf3c4c5383ed Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Sun, 10 Jan 2021 21:29:07 +0900
Subject: [PATCH] Remove possibility of using same seeds

---
 random.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/random.c b/random.c
index 29491fa7fc..4b5965fea9 100644
--- a/random.c
+++ b/random.c
@@ -583,7 +583,7 @@ ruby_fill_random_bytes(void *seed, size_t size, int need_secure)
 static void
 fill_random_seed(uint32_t *seed, size_t cnt)
 {
-    static int n = 0;
+    static rb_atomic_t n = 0;
 #if defined HAVE_CLOCK_GETTIME
     struct timespec tv;
 #elif defined HAVE_GETTIMEOFDAY
@@ -606,7 +606,7 @@ fill_random_seed(uint32_t *seed, size_t cnt)
 #if SIZEOF_TIME_T > SIZEOF_INT
     seed[0] ^= (uint32_t)((time_t)tv.tv_sec >> SIZEOF_INT * CHAR_BIT);
 #endif
-    seed[2] ^= getpid() ^ (n++ << 16);
+    seed[2] ^= getpid() ^ (ATOMIC_FETCH_ADD(n, 1) << 16);
     seed[3] ^= (uint32_t)(VALUE)&seed;
 #if SIZEOF_VOIDP > SIZEOF_INT
     seed[2] ^= (uint32_t)((VALUE)&seed >> SIZEOF_INT * CHAR_BIT);