[Qemu-devel] [PATCH 01/20] monitor: Drop broken, unused asynchronous command interface

[Markus Armbruster <armbru@redhat.com>]

The asynchronous monitor command interface goes back to commit 940cc30
(Jan 2010).  Added a third case to command execution.  The hope back
then according to the commit message was that all commands get
converted to the asynchronous interface, killing off the other two
cases.  Didn't happen.

The initial asynchronous commands balloon and info balloon were
converted back to synchronous long ago (commit 96637bc and d72f32),
with commit messages calling the asynchronous interface "not fully
working" and "deprecated".  The only other user went away in commit
3b5704b.

New code generally uses synchronous commands and asynchronous events.

What exactly is still "not fully working" with asynchronous commands?
Well, here's a bug that defeats actual asynchronous use pretty
reliably: the reply's ID is wrong (and has always been wrong) unless
you use the command synchronously!  To reproduce, we need an
asynchronous command, so we have to go back before the commit 3b5704b.
Run QEMU with spice:

    $ qemu-system-x86_64 -nodefaults -S -spice port=5900,disable-ticketing -qmp stdio
    {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major":
2}, "package": ""}, "capabilities": []}}

Connect a spice client in another terminal:

    $ remote-viewer spice://localhost:5900

Set up a migration destination dummy in a third terminal:

    $ socat TCP-LISTEN:12345 STDIO

Now paste the following into the QMP monitor:

    { "execute": "qmp_capabilities" }
    { "execute": "client_migrate_info", "id": "i1", "arguments": { "protocol": "spice", "hostname": "localhost", "port": 12345 } }
    { "execute": "query-kvm", "id": "i2" }

Produces two replies immediately, one to qmp_capabilities, and one to
query-kvm:

    {"return": {}}
    {"return": {"enabled": false, "present": true}, "id": "i2"}

Both are correct.  Two lines of debug output from libspice-server not
shown.

Now EOF socat's standard input to make it close the connection.  This
makes the asynchronous client_migrate_info complete.  It replies:

    {"return": {}}

Bug: "id": "i1" is missing.  Two lines of debug output from
libspice-server not shown.  Cherry on top: storage for the missing ID
is leaked.

Get rid of this stuff before somebody hurts himself with it.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 include/monitor/monitor.h |  5 ----
 monitor.c                 | 68 ++---------------------------------------------
 2 files changed, 2 insertions(+), 71 deletions(-)

diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
index df67d56..d409b6a 100644
--- a/include/monitor/monitor.h
+++ b/include/monitor/monitor.h
@@ -16,9 +16,6 @@ extern Monitor *default_mon;
 #define MONITOR_USE_CONTROL   0x04
 #define MONITOR_USE_PRETTY    0x08
 
-/* flags for monitor commands */
-#define MONITOR_CMD_ASYNC       0x0001
-
 int monitor_cur_is_qmp(void);
 
 void monitor_init(CharDriverState *chr, int flags);
@@ -43,8 +40,6 @@ void monitor_flush(Monitor *mon);
 int monitor_set_cpu(int cpu_index);
 int monitor_get_cpu_index(void);
 
-typedef void (MonitorCompletion)(void *opaque, QObject *ret_data);
-
 void monitor_set_error(Monitor *mon, QError *qerror);
 void monitor_read_command(Monitor *mon, int show_prompt);
 int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
diff --git a/monitor.c b/monitor.c
index b2561e1..9a0c3b7 100644
--- a/monitor.c
+++ b/monitor.c
@@ -118,12 +118,6 @@
  *
  */
 
-typedef struct MonitorCompletionData MonitorCompletionData;
-struct MonitorCompletionData {
-    Monitor *mon;
-    void (*user_print)(Monitor *mon, const QObject *data);
-};
-
 typedef struct mon_cmd_t {
     const char *name;
     const char *args_type;
@@ -133,10 +127,7 @@ typedef struct mon_cmd_t {
     union {
         void (*cmd)(Monitor *mon, const QDict *qdict);
         int  (*cmd_new)(Monitor *mon, const QDict *params, QObject **ret_data);
-        int  (*cmd_async)(Monitor *mon, const QDict *params,
-                          MonitorCompletion *cb, void *opaque);
     } mhandler;
-    int flags;
     /* @sub_table is a list of 2nd level of commands. If it do not exist,
      * mhandler should be used. If it exist, sub_table[?].mhandler should be
      * used, and mhandler of 1st level plays the role of help function.
@@ -394,11 +385,6 @@ static inline int handler_is_qobject(const mon_cmd_t *cmd)
     return cmd->user_print != NULL;
 }
 
-static inline bool handler_is_async(const mon_cmd_t *cmd)
-{
-    return cmd->flags & MONITOR_CMD_ASYNC;
-}
-
 static inline int monitor_has_error(const Monitor *mon)
 {
     return mon->error != NULL;
@@ -917,45 +903,6 @@ static void hmp_trace_file(Monitor *mon, const QDict *qdict)
 }
 #endif
 
-static void user_monitor_complete(void *opaque, QObject *ret_data)
-{
-    MonitorCompletionData *data = (MonitorCompletionData *)opaque; 
-
-    if (ret_data) {
-        data->user_print(data->mon, ret_data);
-    }
-    monitor_resume(data->mon);
-    g_free(data);
-}
-
-static void qmp_monitor_complete(void *opaque, QObject *ret_data)
-{
-    monitor_protocol_emitter(opaque, ret_data);
-}
-
-static int qmp_async_cmd_handler(Monitor *mon, const mon_cmd_t *cmd,
-                                 const QDict *params)
-{
-    return cmd->mhandler.cmd_async(mon, params, qmp_monitor_complete, mon);
-}
-
-static void user_async_cmd_handler(Monitor *mon, const mon_cmd_t *cmd,
-                                   const QDict *params)
-{
-    int ret;
-
-    MonitorCompletionData *cb_data = g_malloc(sizeof(*cb_data));
-    cb_data->mon = mon;
-    cb_data->user_print = cmd->user_print;
-    monitor_suspend(mon);
-    ret = cmd->mhandler.cmd_async(mon, params,
-                                  user_monitor_complete, cb_data);
-    if (ret < 0) {
-        monitor_resume(mon);
-        g_free(cb_data);
-    }
-}
-
 static void hmp_info_help(Monitor *mon, const QDict *qdict)
 {
     help_cmd(mon, "info");
@@ -4121,9 +4068,7 @@ static void handle_user_command(Monitor *mon, const char *cmdline)
     if (!cmd)
         goto out;
 
-    if (handler_is_async(cmd)) {
-        user_async_cmd_handler(mon, cmd, qdict);
-    } else if (handler_is_qobject(cmd)) {
+    if (handler_is_qobject(cmd)) {
         QObject *data = NULL;
 
         /* XXX: ignores the error code */
@@ -5134,16 +5079,7 @@ static void handle_qmp_command(JSONMessageParser *parser, QList *tokens)
         goto err_out;
     }
 
-    if (handler_is_async(cmd)) {
-        err = qmp_async_cmd_handler(mon, cmd, args);
-        if (err) {
-            /* emit the error response */
-            goto err_out;
-        }
-    } else {
-        qmp_call_cmd(mon, cmd, args);
-    }
-
+    qmp_call_cmd(mon, cmd, args);
     goto out;
 
 err_out:
-- 
1.9.3