Re: [Qemu-devel] [PATCH 0/5] qemu-char/monitor: make monitor_puts thread safe

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 27 Jun 2014 11:43:20 +0200
Stefan Hajnoczi <stefanha@redhat.com> wrote:

> On Tue, Jun 03, 2014 at 06:39:05PM +0200, Paolo Bonzini wrote:
> > Even though virtio-blk-dataplane mostly synchronizes with the block layer
> > by means of the AioContext, we still need to introduce mutexes for other
> > QEMU subsystems that the dataplane thread might encounter on its way.
> > Adding rerror/werror support, for example, means that the dataplane
> > thread will have to generate QMP events.
> > 
> > monitor_puts is the entry point for generating QMP responses and events.
> > Making it thread-safe lets virtio-blk-dataplane threads generate QMP
> > events; because the same entry point is also used for responses, a
> > response and an event will never be intertwined.
> > 
> > Protection is inserted at both the qemu-char and monitor levels.
> > A generic mutex is necessary in qemu_fe_chr_write so that
> > qemu_chr_fe_write_all does not break its output; we reuse that
> > mutex in some of the character devices.
> > 
> > There is no need to protect against removal of the monitor's backend,
> > since the monitor itself cannot be removed.
> > 
> > Paolo Bonzini (6):
> >   qemu-char: introduce qemu_chr_alloc
> >   qemu-char: do not call chr_write directly
> >   qemu-char: move pty_chr_update_read_handler around
> >   qemu-char: make writes thread-safe
> >   monitor: protect outbuf with mutex
> >   monitor: protect event emission
> > 
> >  backends/baum.c       |   2 +-
> >  backends/msmouse.c    |   2 +-
> >  include/sysemu/char.h |  20 ++++++--
> >  monitor.c             |  55 ++++++++++++++++++----
> >  qemu-char.c           | 125 +++++++++++++++++++++++++++++++++-----------------
> >  spice-qemu-char.c     |   2 +-
> >  ui/console.c          |   2 +-
> >  7 files changed, 149 insertions(+), 59 deletions(-)
> 
> Modulo Fam's missing unlock comment:
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

I appreciate your review, but this one is already merged on master.