From: Maxim Levitsky <mlevitsk@redhat.com>
Date: Tue, 6 Oct 2020 15:38:53 +0300
Subject: qtest: Reintroduce qtest_qmp_receive with QMP event buffering

Git-commit: c22045bfe6d5ceebd414ff53ff23fff7ad5930d1
References: bsc#1184574

The new qtest_qmp_receive buffers all the received qmp events, allowing
qtest_qmp_eventwait_ref to return them.

This is intended to solve the race in regard to ordering of qmp events
vs qmp responses, as soon as the callers start using the new interface.

In addition to that, define qtest_qmp_event_ref a function which only scans
the buffer that qtest_qmp_receive stores the events to.  This is intended
for callers that are only interested in events that were received during
the last call to the qtest_qmp_receive.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201006123904.610658-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Lin Ma <lma@suse.com>
---
 tests/libqtest.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 tests/libqtest.h | 23 +++++++++++++++++++++++
 2 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/tests/libqtest.c b/tests/libqtest.c
index a6c446237f06a379880849012103..80476fef3edb1e6bd7ceff832859 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -45,6 +45,7 @@ struct QTestState
     bool big_endian;
     bool irq_level[MAX_IRQ];
     GString *rx;
+    GList *pending_events;
 };
 
 static GHookList abrt_hooks;
@@ -250,6 +251,7 @@ QTestState *qtest_init_without_qmp_handshake(const char *extra_args)
 
     g_test_message("starting QEMU: %s", command);
 
+    s->pending_events = NULL;
     s->wstatus = 0;
     s->expected_status = 0;
     s->qemu_pid = fork();
@@ -357,6 +359,13 @@ void qtest_quit(QTestState *s)
     close(s->fd);
     close(s->qmp_fd);
     g_string_free(s->rx, true);
+
+    for (GList *it = s->pending_events; it != NULL; it = it->next) {
+        qobject_unref((QDict *)it->data);
+    }
+
+    g_list_free(s->pending_events);
+
     g_free(s);
 }
 
@@ -575,6 +584,19 @@ QDict *qmp_fd_receive(int fd)
     return qmp.response;
 }
 
+QDict *qtest_qmp_receive(QTestState *s)
+{
+    while (true) {
+        QDict *response = qtest_qmp_receive_dict(s);
+
+        if (!qdict_get_try_str(response, "event")) {
+            return response;
+        }
+        /* Stash the event for a later consumption */
+        s->pending_events = g_list_prepend(s->pending_events, response);
+    }
+}
+
 QDict *qtest_qmp_receive_dict(QTestState *s)
 {
     return qmp_fd_receive(s->qmp_fd);
@@ -743,10 +765,34 @@ void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
     va_end(ap);
 }
 
-QDict *qtest_qmp_eventwait_ref(QTestState *s, const char *event)
+QDict *qtest_qmp_event_ref(QTestState *s, const char *event)
 {
+    GList *next = NULL;
     QDict *response;
 
+    for (GList *it = s->pending_events; it != NULL; it = next) {
+
+        next = it->next;
+        response = (QDict *)it->data;
+
+        s->pending_events = g_list_remove_link(s->pending_events, it);
+
+        if (!strcmp(qdict_get_str(response, "event"), event)) {
+            return response;
+        }
+        qobject_unref(response);
+    }
+    return NULL;
+}
+
+QDict *qtest_qmp_eventwait_ref(QTestState *s, const char *event)
+{
+    QDict *response = qtest_qmp_event_ref(s, event);
+
+    if (response) {
+        return response;
+    }
+
     for (;;) {
         response = qtest_qmp_receive_dict(s);
         if ((qdict_haskey(response, "event")) &&
diff --git a/tests/libqtest.h b/tests/libqtest.h
index 63818d0d607765cdafe5ed0354e2..a8d0aea4d4e871ef35bbaf481fcb 100644
--- a/tests/libqtest.h
+++ b/tests/libqtest.h
@@ -198,6 +198,16 @@ void qtest_qmp_vsend(QTestState *s, const char *fmt, va_list ap)
  */
 QDict *qtest_qmp_receive_dict(QTestState *s);
 
+/**
+ * qtest_qmp_receive:
+ * @s: #QTestState instance to operate on.
+ *
+ * Reads a QMP message from QEMU and returns the response.
+ * Buffers all the events received meanwhile, until a
+ * call to qtest_qmp_eventwait
+ */
+QDict *qtest_qmp_receive(QTestState *s);
+
 /**
  * qtest_qmp_eventwait:
  * @s: #QTestState instance to operate on.
@@ -217,6 +227,19 @@ void qtest_qmp_eventwait(QTestState *s, const char *event);
  */
 QDict *qtest_qmp_eventwait_ref(QTestState *s, const char *event);
 
+/**
+ * qtest_qmp_event_ref:
+ * @s: #QTestState instance to operate on.
+ * @event: event to return.
+ *
+ * Removes non-matching events from the buffer that was set by
+ * qtest_qmp_receive, until an event bearing the given name is found,
+ * and returns it.
+ * If no event matches, clears the buffer and returns NULL.
+ *
+ */
+QDict *qtest_qmp_event_ref(QTestState *s, const char *event);
+
 /**
  * qtest_qmp_receive_success:
  * @s: #QTestState instance to operate on
