libqtest: add qtest_kill_qemu()

Tests that manage multiple processes may wish to kill QEMU before
destroying the QTestState. Expose a function to do that.

The vhost-user-blk-test testcase will need this.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-Id: <20210223144653.811468-4-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qtest/libqos/libqtest.h

@@ -74,6 +74,17 @@ QTestState *qtest_init_without_qmp_handshake(const char *extra_args);
  */
 QTestState *qtest_init_with_serial(const char *extra_args, int *sock_fd);
 
+/**
+ * qtest_kill_qemu:
+ * @s: #QTestState instance to operate on.
+ *
+ * Kill the QEMU process and wait for it to terminate. It is safe to call this
+ * function multiple times. Normally qtest_quit() is used instead because it
+ * also frees QTestState. Use qtest_kill_qemu() when you just want to kill QEMU
+ * and qtest_quit() will be called later.
+ */
+void qtest_kill_qemu(QTestState *s);
+
 /**
  * qtest_quit:
  * @s: #QTestState instance to operate on.

tests/qtest/libqtest.c

@@ -133,7 +133,7 @@ void qtest_set_expected_status(QTestState *s, int status)
     s->expected_status = status;
 }
 
-static void kill_qemu(QTestState *s)
+void qtest_kill_qemu(QTestState *s)
 {
     pid_t pid = s->qemu_pid;
     int wstatus;
@@ -143,6 +143,7 @@ static void kill_qemu(QTestState *s)
         kill(pid, SIGTERM);
         TFR(pid = waitpid(s->qemu_pid, &s->wstatus, 0));
         assert(pid == s->qemu_pid);
+        s->qemu_pid = -1;
     }
 
     /*
@@ -169,7 +170,7 @@ static void kill_qemu(QTestState *s)
 
 static void kill_qemu_hook_func(void *s)
 {
-    kill_qemu(s);
+    qtest_kill_qemu(s);
 }
 
 static void sigabrt_handler(int signo)
@@ -373,7 +374,7 @@ void qtest_quit(QTestState *s)
     /* Uninstall SIGABRT handler on last instance */
     cleanup_sigabrt_handler();
 
-    kill_qemu(s);
+    qtest_kill_qemu(s);
     close(s->fd);
     close(s->qmp_fd);
     g_string_free(s->rx, true);