shutdown: Simplify shutdown_signal

There is no signal 0 (kill(pid, 0) has special semantics to probe whether
a process is alive), rather than actually sending a signal 0).  So we
can use the simpler 0, instead of -1, for our sentinel of whether a
shutdown request due to a signal has happened.

Suggested-by: Markus Armbruster <[email protected]>
Signed-off-by: Eric Blake <[email protected]>
Reviewed-by: Markus Armbruster <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Message-Id: <20170515214114[email protected]>
Signed-off-by: Markus Armbruster <[email protected]>

diff --git a/vl.c b/vl.c
index 1512df6e9ef340a8e5b615b9f6015105ce8eb593..b42b0b32a01eb3415f3872ba965dfab35139a6f7 100644 (file)
--- a/vl.c
+++ b/vl.c
@@ -1598,7 +1598,7 @@ void vm_state_notify(int running, RunState state)
 }
 
 static int reset_requested;
-static int shutdown_requested, shutdown_signal = -1;
+static int shutdown_requested, shutdown_signal;
 static pid_t shutdown_pid;
 static int powerdown_requested;
 static int debug_requested;
@@ -1629,7 +1629,7 @@ static int qemu_shutdown_requested(void)
 
 static void qemu_kill_report(void)
 {
-    if (!qtest_driver() && shutdown_signal != -1) {
+    if (!qtest_driver() && shutdown_signal) {
         if (shutdown_pid == 0) {
             /* This happens for eg ^C at the terminal, so it's worth
              * avoiding printing an odd message in that case.
@@ -1643,7 +1643,7 @@ static void qemu_kill_report(void)
                          shutdown_cmd ? shutdown_cmd : "<unknown process>");
             g_free(shutdown_cmd);
         }
-        shutdown_signal = -1;
+        shutdown_signal = 0;
     }
 }