From d0e323971e9a35f494dfe2bd8d652b89e2e08661 Mon Sep 17 00:00:00 2001
From: Trevor Norris <trev.norris@gmail.com>
Date: Tue, 17 Mar 2020 11:03:54 -0600
Subject: [PATCH] zos: fix potential event loop stall

This is a port of 70002c80 to z/OS to fix the same potential issue that
could effectively enter an infinite loop (but not a busy loop) under
certain conditions when polling for events.

PR-URL: https://github.com/libuv/libuv/pull/2725
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Jameson Nash <vtjnash@gmail.com>
---
 src/unix/os390.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/unix/os390.c b/src/unix/os390.c
index dce169b9..458e7310 100644
--- a/src/unix/os390.c
+++ b/src/unix/os390.c
@@ -887,12 +887,13 @@ void uv__io_poll(uv_loop_t* loop, int timeout) {
     if (nfds == 0) {
       assert(timeout != -1);
 
-      if (timeout > 0) {
-        timeout = real_timeout - timeout;
-        continue;
-      }
+      if (timeout == 0)
+        return;
 
-      return;
+      /* We may have been inside the system call for longer than |timeout|
+       * milliseconds so we need to update the timestamp to avoid drift.
+       */
+      goto update_timeout;
     }
 
     if (nfds == -1) {