1 files changed, 4 insertions, 0 deletions
diff --git a/thread.c b/thread.c
index 9f723d0d64..dce0ca800f 100644
--- a/thread.c
+++ b/thread.c
@@ -5210,6 +5210,10 @@ ruby_kill(rb_pid_t pid, int sig)
     rb_thread_t *th = GET_THREAD();
     rb_vm_t *vm = GET_VM();
 
+    /*
+     * When target pid is self, many caller assume signal will be
+     * delivered immediately and synchronously.
+     */
     if ((th == vm->main_thread) && (pid == getpid())) {
 	GVL_UNLOCK_BEGIN();
 	native_mutex_lock(&th->interrupt_lock);