Re: [Qemu-devel] [PATCH] New API for asynchronous monitor commands (V2)

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 28 Jan 2010 19:29:22 +0100
Kevin Wolf <kwolf@redhat.com> wrote:

> 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 <agl@us.ibm.com>
> 
> 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?

 Breaks others 'info' commands as well, I've submitted a proper fix already:

http://lists.gnu.org/archive/html/qemu-devel/2010-01/msg01965.html