[Qemu-devel] Re: [PATCH 2/2] qemu-io: check registered fds in command_loop()

[Kevin Wolf <kwolf@redhat.com>]

Am 15.06.2010 19:53, schrieb MORITA Kazutaka:
> Some block drivers use an aio handler and do I/O completion routines
> in it.  However, the handler is not invoked if we only do
> aio_read/write, because registered fds are not checked at all.
> 
> This patch registers a command processing function as a fd handler to
> STDIO, and calls qemu_aio_wait() in command_loop().  Any other
> handlers can be invoked when user input is idle.
> 
> Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>

This breaks qemu-iotests. The reason is that synchronous requests get
out of order. Previously, do_aio_readv/writev waited until the request
was completed, and only afterwards the next command was read from stdio.
Now the next command can start during the qemu_aio_wait() that
do_aio_readv/writev uses internally to wait.

So we either need to deregister the fd handler while a command is
running, or (more cleanly) have an async_context_push/pop for any
command except aio_*.

Kevin