[PATCH] system/qtest.c: Allow for multiple CHR_EVENT_CLOSED events

[Peter Maydell <peter.maydell@linaro.org>]

In the qtest_event() QEMUChrEvent handler, we create a timer
and log OPENED on CHR_EVENT_OPENED, and we destroy the timer and
log CLOSED on CHR_EVENT_CLOSED. However, the chardev subsystem
can send us more than one CHR_EVENT_CLOSED if we're reading from
a file chardev:
 * the first one happens when we read the last data from the file
 * the second one happens when the user hits ^C to exit QEMU
   and the chardev is finalized: char_fd_finalize()

This causes us to call g_timer_elapsed() with a NULL timer
(which glib complains about) and print an extra CLOSED log line
with a zero timestamp:

[I +0.063829] CLOSED
qemu-system-aarch64: GLib: g_timer_elapsed: assertion 'timer != NULL' failed
[I +0.000000] CLOSED

Avoid this by ignoring a CHR_EVENT_CLOSED if we have already
processed one.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 system/qtest.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/system/qtest.c b/system/qtest.c
index baef06d4d1b..67e2385f4b0 100644
--- a/system/qtest.c
+++ b/system/qtest.c
@@ -815,6 +815,10 @@ static void qtest_event(void *opaque, QEMUChrEvent event)
         }
         break;
     case CHR_EVENT_CLOSED:
+        if (!qtest_opened) {
+            /* Ignore CLOSED events if we have already closed the log */
+            break;
+        }
         qtest_opened = false;
         if (qtest_log_fp) {
             fprintf(qtest_log_fp, "[I +" FMT_timeval "] CLOSED\n", g_timer_elapsed(timer, NULL));
-- 
2.43.0