Re: [Qemu-devel] [PATCH V8 00/13] monitor: support sub command group in auto completion and help

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 30 Jul 2013 12:03:11 -0400
Luiz Capitulino <lcapitulino@redhat.com> wrote:

> On Fri, 26 Jul 2013 11:20:29 +0800
> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> 
> > This series make auto completion and help functions works normal for sub
> > command, by using reentrant functions. In order to do that, global variables
> > are not directly used in those functions any more. With this series, cmd_table
> > is a member of structure Monitor so it is possible to create a monitor with
> > different command table now, auto completion will work in that monitor. In
> > short, "info" is not treated as a special case now, this series ensure help
> > and auto complete function works normal for any sub command added in the future.
> > 
> > Patch 5 replaced cur_mon with rs->mon, it is safe because:
> > monitor_init() calls readline_init() which initialize mon->rs, result is
> > mon->rs->mon == mon. Then qemu_chr_add_handlers() is called, which make
> > monitor_read() function take *mon as its opaque. Later, when user input,
> > monitor_read() is called, where cur_mon is set to *mon by "cur_mon = opaque".
> > If qemu's monitors run in one thread, then later in readline_handle_byte()
> > and readline_comletion(), cur_mon is actually equal to rs->mon, in another
> > word, it points to the monitor instance, so it is safe to replace *cur_mon
> > in those functions.
> 
> I've applied this to qmp-next with the change I suggested for
> patch 09/13.

Unfortunately this series brakes make check:

GTESTER check-qtest-x86_64
Broken pipe
GTester: last random seed: R02S3492bd34f44dd17460851643383be44d
main-loop: WARNING: I/O thread spun for 1000 iterations
make: *** [check-qtest-x86_64] Error 1

I debugged it (with some help from Laszlo) and the problem is that it
broke the human-monitor-command command. Any usage of this command
triggers the bug like:

{ "execute": "human-monitor-command",
             "arguments": { "command-line": "info registers" } }

It seems simple to fix, I think you just have to initialize
mon->cmd_table in qmp_human_monitor_command(), but I'd recommend two
things:

 1. It's better to split off some/all QMP initialization from
    monitor_init() and call it from qmp_human_monitor_command()

 2. Can you please take the opportunity and test all commands using
    cur_mon? Just grep for it

Sorry for noticing this only now, but I only run make check before
sending a pull request (although this very likely shows you didn't
run it either).