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Re: [Qemu-devel] [PATCH] New API for asynchronous monitor commands (V2)
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH] New API for asynchronous monitor commands (V2) |
Date: |
Thu, 28 Jan 2010 19:29:22 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 |
Am 25.01.2010 19:18, schrieb Adam Litke:
> Changes since V1:
> - Miscellaneous code cleanups (Thanks Luiz)
>
> Qemu has a number of commands that can operate asynchronously (savevm,
> migrate,
> etc) and it will be getting more. For these commands, the user monitor needs
> to be suspended, but QMP monitors could continue to to accept other commands.
> This patch introduces a new command API that isolates the details of handling
> different monitor types from the actual command execution.
>
> A monitor command can use this API by implementing the mhandler.cmd_async
> handler (or info_async if appropriate). This function is responsible for
> submitting the command and does not return any data although it may raise
> errors. When the command completes, the QMPCompletion callback should be
> invoked with its opaque data and the command result.
>
> The process for submitting and completing an asynchronous command is different
> for QMP and user monitors. A user monitor must be suspended at submit time
> and
> resumed at completion time. The user_print() function must be passed to the
> QMPCompletion callback so the result can be displayed properly. QMP monitors
> are simpler. No submit time setup is required. When the command completes,
> monitor_protocol_emitter() writes the result in JSON format.
>
> This API can also be used to implement synchronous commands. In this case,
> the
> cmd_async handler should immediately call the QMPCompletion callback. It is
> my
> hope that this new interface will work for all commands, leading to a
> drastically simplified monitor.c once all commands are ported.
>
> Thanks to Anthony for helping me out with the initial design.
>
> Signed-off-by: Adam Litke <address@hidden>
This commit introduces a segfault on info pci for me. The following
patch seems to make it work again. Is it correct or is rather info pci
doing something wrong?
diff --git a/monitor.c b/monitor.c
index fbae5ce..22690c4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3700,7 +3700,12 @@ static void monitor_print_error(Monitor *mon)
static int is_async_return(const QObject *data)
{
- return data && qdict_haskey(qobject_to_qdict(data), "__mon_async");
+ const QDict *dict = NULL;
+
+ if (data != NULL) {
+ dict = qobject_to_qdict(data);
+ }
+ return dict && qdict_haskey(dict, "__mon_async");
}
static void monitor_call_handler(Monitor *mon, const mon_cmd_t *cmd,
Kevin