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

[Stefan Hajnoczi]

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 <address@hidden>

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