From 4a9364082e8f1b2cf022cb372fb4ad5f845ea38d Mon Sep 17 00:00:00 2001
From: Yuval Tassa <tassa@google.com>
Date: Sat, 4 Jul 2026 12:07:06 -0700
Subject: [PATCH] Fix data race lazy-init spin lock deadlock on Windows.

PiperOrigin-RevId: 942556300
Change-Id: Iffe7a3e71c0f6273603e2ada14bf8d924b0ee6cf
---
 src/engine/engine_util_errmem.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/engine/engine_util_errmem.c b/src/engine/engine_util_errmem.c
index f6c51988..9eb93992 100644
--- a/src/engine/engine_util_errmem.c
+++ b/src/engine/engine_util_errmem.c
@@ -21,6 +21,12 @@
 #include <string.h>
 #include <time.h>
 
+#if defined(_WIN32)
+#include <windows.h>
+#elif defined(__unix__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__EMSCRIPTEN__)
+#include <sched.h>
+#endif
+
 #if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
 #include <unistd.h>
 #endif
@@ -152,7 +158,11 @@ static const mjLogConfig* mju_getLogConfigPtr(void) {
     } else {
       // another thread is initializing; spin until it completes
       while (!mj_atomic_load_bool(&env_init_done)) {
-        // empty
+#if defined(_WIN32)
+        Sleep(0);
+#elif defined(__unix__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__EMSCRIPTEN__)
+        sched_yield();
+#endif
       }
     }
   }