zos: fix timeout for condition variable

The pthread_cond_timedwait requires a timeout relative to the Epoch.
So don't use uv__hrtime to set the timeout because it is relative to an
arbitrary time in the past. Use gettimeofday instead.

PR-URL: https://github.com/libuv/libuv/pull/1711
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jamie Davis <davisjam@vt.edu>

2 files changed, 18 insertions, 2 deletions

diff --git a/docs/src/threading.rst b/docs/src/threading.rst
index bca8ba1d..89bb4a6f 100644
--- a/docs/src/threading.rst
+++ b/docs/src/threading.rst
@@ -131,8 +131,15 @@ Functions return 0 on success or an error code < 0 (unless the
 return type is void, of course).
 
 .. note::
-    Callers should be prepared to deal with spurious wakeups on :c:func:`uv_cond_wait` and
-    :c:func:`uv_cond_timedwait`.
+    1. Callers should be prepared to deal with spurious wakeups on :c:func:`uv_cond_wait`
+       and :c:func:`uv_cond_timedwait`.
+    2. The timeout parameter for :c:func:`uv_cond_timedwait` is relative to the time
+       at which function is called.
+    3. On z/OS, the timeout parameter for :c:func:`uv_cond_timedwait` is converted to an
+       absolute system time at which the wait expires. If the current system clock time
+       passes the absolute time calculated before the condition is signaled, an ETIMEDOUT
+       error results. After the wait begins, the wait time is not affected by changes
+       to the system clock.
 
 .. c:function:: int uv_cond_init(uv_cond_t* cond)
 .. c:function:: void uv_cond_destroy(uv_cond_t* cond)
diff --git a/src/unix/thread.c b/src/unix/thread.c
index 8229c275..3def2945 100644
--- a/src/unix/thread.c
+++ b/src/unix/thread.c
@@ -646,13 +646,22 @@ void uv_cond_wait(uv_cond_t* cond, uv_mutex_t* mutex) {
 int uv_cond_timedwait(uv_cond_t* cond, uv_mutex_t* mutex, uint64_t timeout) {
   int r;
   struct timespec ts;
+#if defined(__MVS__)
+  struct timeval tv;
+#endif
 
 #if defined(__APPLE__) && defined(__MACH__)
   ts.tv_sec = timeout / NANOSEC;
   ts.tv_nsec = timeout % NANOSEC;
   r = pthread_cond_timedwait_relative_np(cond, mutex, &ts);
 #else
+#if defined(__MVS__)
+  if (gettimeofday(&tv, NULL))
+    abort();
+  timeout += tv.tv_sec * NANOSEC + tv.tv_usec * 1e3;
+#else
   timeout += uv__hrtime(UV_CLOCK_PRECISE);
+#endif
   ts.tv_sec = timeout / NANOSEC;
   ts.tv_nsec = timeout % NANOSEC;
 #if defined(__ANDROID_API__) && __ANDROID_API__ < 21