diff --git a/include/aws/common/private/thread_shared.h b/include/aws/common/private/thread_shared.h
index ca263e56c..19e648319 100644
--- a/include/aws/common/private/thread_shared.h
+++ b/include/aws/common/private/thread_shared.h
@@ -36,4 +36,9 @@ AWS_COMMON_API void aws_thread_initialize_thread_management(void);
  */
 AWS_COMMON_API size_t aws_thread_get_managed_thread_count(void);
 
+/**
+ * The handler before fork in the parent process.
+ */
+void aws_pthread_atfork_on_fork_prepare(void);
+
 #endif /* AWS_COMMON_PRIVATE_THREAD_SHARED_H */
diff --git a/source/common.c b/source/common.c
index a391f4fcb..eed29174b 100644
--- a/source/common.c
+++ b/source/common.c
@@ -390,6 +390,12 @@ void aws_common_library_init(struct aws_allocator *allocator) {
             AWS_LOGF_INFO(AWS_LS_COMMON_GENERAL, "static: libnuma.so failed to load");
         }
 #endif
+
+#ifndef AWS_OS_WINDOWS
+        if (pthread_atfork(aws_pthread_atfork_on_fork_prepare, NULL, NULL) != 0) {
+            AWS_LOGF_INFO(AWS_LS_COMMON_GENERAL, "static: failed to register pthread at fork");
+        }
+#endif
     }
 }
 
diff --git a/source/posix/cross_process_lock.c b/source/posix/cross_process_lock.c
index 1ef5d2b5f..f94834184 100644
--- a/source/posix/cross_process_lock.c
+++ b/source/posix/cross_process_lock.c
@@ -133,7 +133,6 @@ struct aws_cross_process_lock *aws_cross_process_lock_try_acquire(
 
 void aws_cross_process_lock_release(struct aws_cross_process_lock *instance_lock) {
     if (instance_lock) {
-        flock(instance_lock->locked_fd, LOCK_UN);
         close(instance_lock->locked_fd);
         AWS_LOGF_TRACE(AWS_LS_COMMON_GENERAL, "static: Lock file released for fd %d", instance_lock->locked_fd);
         aws_mem_release(instance_lock->allocator, instance_lock);
diff --git a/source/thread_shared.c b/source/thread_shared.c
index bd479a16e..e3c414aaf 100644
--- a/source/thread_shared.c
+++ b/source/thread_shared.c
@@ -165,3 +165,19 @@ void aws_thread_pending_join_add(struct aws_linked_list_node *node) {
 void aws_thread_initialize_thread_management(void) {
     aws_linked_list_init(&s_pending_join_managed_threads);
 }
+
+void aws_pthread_atfork_on_fork_prepare(void) {
+    /**
+     * The handler before fork in the parent process.
+     *
+     * Clean up the s_pending_join_managed_threads now, the list is created by the parent process and should not be used
+     * in child process.
+     * Fork will copy the list, but not the real threads.
+     */
+    struct aws_linked_list empty;
+    aws_linked_list_init(&empty);
+    aws_mutex_lock(&s_managed_thread_lock);
+    aws_linked_list_swap_contents(&empty, &s_pending_join_managed_threads);
+    aws_mutex_unlock(&s_managed_thread_lock);
+    aws_thread_join_and_free_wrapper_list(&empty);
+}