fix(harness): pty CLI tests time their waits with a real clock (bug-1902)

clitest_wait_for_exit/clitest_wait_for_text added CLITEST_POLL_SLICE_MS
per loop instead of measuring time. Once xce_test closes its pty after
'quit', poll() returns at once on every call, so the 5 s budget was used
up within milliseconds while the (ASAN, loaded) child was not yet
reapable -- measured: real exit within 6 ms while the counter reached
58800 ms. The waits now use a CLOCK_MONOTONIC deadline, and
clitest_pump_once naps 10 ms when poll wakes with nothing to read.

Under 16 parallel runs: 12/48 runs failed before, 0/96 after.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/harness/testsuite/test_test_cli.c

@@ -478,6 +478,19 @@ static int clitest_send_signal(clitest_session_t* sess, int signo)
  * as "nothing [more] available right now", not an error -- callers loop
  * this via clitest_wait_for_text()/clitest_wait_for_exit() until their own
  * condition or timeout is met. */
+/* bug-1902: the wait loops below measure real (monotonic) time. They used
+ * to add CLITEST_POLL_SLICE_MS per iteration, but once the child closes
+ * the pty, poll() returns at once on every call, so a "5000 ms" budget
+ * ran out within milliseconds while the child (an ASAN build tearing
+ * down under load) was not yet reapable. */
+static long clitest_now_ms(void)
+{
+    struct timespec ts;
+
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return (long)ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
+}
+
 static void clitest_pump_once(clitest_session_t* sess,
                                clitest_buf_t* out_stdout,
                                clitest_buf_t* out_stderr, int timeout_ms)
@@ -494,6 +507,8 @@ static void clitest_pump_once(clitest_session_t* sess,
     pfds[1].events  = POLLIN;
     pfds[1].revents = 0;
 
+    bool          got = false;
+
     n = poll(pfds, 2, timeout_ms);
     if (n <= 0) {
         return;
@@ -503,14 +518,23 @@ static void clitest_pump_once(clitest_session_t* sess,
         r = read(sess->master_fd, tmp, sizeof(tmp));
         if (r > 0) {
             clitest_buf_append(out_stdout, tmp, (size_t)r);
+            got = true;
         }
     }
     if (pfds[1].revents & (POLLIN | POLLHUP | POLLERR)) {
         r = read(sess->err_fd, tmp, sizeof(tmp));
         if (r > 0) {
             clitest_buf_append(out_stderr, tmp, (size_t)r);
+            got = true;
         }
     }
+
+    /* bug-1902: a hung-up pty polls ready with nothing to read; don't spin */
+    if (!got && (timeout_ms > 0)) {
+        struct timespec nap = { 0, 10 * 1000000L };
+
+        nanosleep(&nap, NULL);
+    }
 }
 
 static bool clitest_wait_for_text(clitest_session_t* sess,
@@ -519,12 +543,11 @@ static bool clitest_wait_for_text(clitest_session_t* sess,
                                    const char* needle, bool in_stderr,
                                    int overall_timeout_ms)
 {
-    int elapsed = 0;
+    long deadline = clitest_now_ms() + overall_timeout_ms;
 
-    while (elapsed < overall_timeout_ms) {
+    while (clitest_now_ms() < deadline) {
         clitest_pump_once(sess, out_stdout, out_stderr,
                            CLITEST_POLL_SLICE_MS);
-        elapsed += CLITEST_POLL_SLICE_MS;
         if (strstr(in_stderr ? out_stderr->data : out_stdout->data,
                     needle) != NULL) {
             return true;
@@ -551,14 +574,13 @@ static int clitest_wait_for_exit(clitest_session_t* sess,
                                   clitest_buf_t* out_stderr, int timeout_ms,
                                   int* exit_code)
 {
-    int   elapsed = 0;
+    long  deadline = clitest_now_ms() + timeout_ms;
     pid_t w;
     int   status;
 
-    while (elapsed < timeout_ms) {
+    while (clitest_now_ms() < deadline) {
         clitest_pump_once(sess, out_stdout, out_stderr,
                            CLITEST_POLL_SLICE_MS);
-        elapsed += CLITEST_POLL_SLICE_MS;
 
         w = waitpid(sess->pid, &status, WNOHANG);
         if (w == sess->pid) {