1 files changed, 11 insertions, 0 deletions
diff --git a/thread.c b/thread.c
index 1364d73be2..e1b194861a 100644
--- a/thread.c
+++ b/thread.c
@@ -1675,6 +1675,12 @@ rb_thread_io_blocking_region(rb_blocking_function_t *func, void *data1, int fd)
         .th = rb_ec_thread_ptr(ec)
     };
 
+    // `errno` is only valid when there is an actual error - but we can't
+    // extract that from the return value of `func` alone, so we clear any
+    // prior `errno` value here so that we can later check if it was set by
+    // `func` or not (as opposed to some previously set value).
+    errno = 0;
+
     RB_VM_LOCK_ENTER();
     {
         ccan_list_add(&rb_ec_vm_ptr(ec)->waiting_fds, &waiting_fd.wfd_node);
@@ -1706,6 +1712,11 @@ rb_thread_io_blocking_region(rb_blocking_function_t *func, void *data1, int fd)
     /* TODO: check func() */
     RUBY_VM_CHECK_INTS_BLOCKING(ec);
 
+    // If the error was a timeout, we raise a specific exception for that:
+    if (saved_errno == ETIMEDOUT) {
+        rb_raise(rb_eIOTimeoutError, "Blocking operation timed out!");
+    }
+
     errno = saved_errno;
 
     return val;