Re: [Qemu-devel] [PATCH v7 19/23] qmp: isolate responses into io thread

[Stefan Hajnoczi]

On Wed, Jan 24, 2018 at 01:39:53PM +0800, Peter Xu wrote:
> For those monitors who have enabled IO thread, we'll offload the
> responding procedure into IO thread.  The main reason is that chardev is
> not thread safe, and we need to do all the read/write IOs in the same
> thread.  For use_io_thr=true monitors, that thread is the IO thread.
> 
> We do this isolation in similar pattern as what we have done to the
> request queue: we first create one response queue for each monitor, then
> instead of replying directly in the main thread, we queue the responses
> and kick the IO thread to do the rest of the job for us.
> 
> A funny thing after doing this is that, when the QMP clients send "quit"
> to QEMU, it's possible that we close the IOThread even earlier than
> replying to that "quit".  So another thing we need to do before cleaning
> up the monitors is that we need to flush the response queue (we don't
> need to do that for command queue; after all we are quitting) to make
> sure replies for handled commands are always flushed back to clients.
> 
> Reviewed-by: Fam Zheng <address@hidden>
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  monitor.c | 96 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 95 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <address@hidden>

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