Il 05/06/2014 10:12, Stefan Hajnoczi ha scritto:
On Wed, Jun 04, 2014 at 08:02:06PM +0200, Paolo Bonzini wrote:
Il 04/06/2014 14:37, Stefan Hajnoczi ha scritto:
Why is this design cleaner? Because NBD code doesn't have to worry
about fd handlers. It uses straightforward coroutine send/recv for
socket I/O inside nbd_read_req() and nbd_write_resp(). It's easy to see
that only one coroutine receives from the socket and that only one
coroutine writes to the socket.
I don't understand how this would work without managing fd handlers.
fd handlers still need to be managed, but not by NBD code. They must be
managed by coroutine recv/send utility functions. In other words, fd
handlers are used locally, not globally.
def co_recv(fd, buf):
while True:
nbytes = recv(fd, buf, len(buf))
if nbytes == -1:
if errno == EINTR:
continue
if errno == EAGAIN or errno == EWOULDBLOCK:
aio_set_fd_read_handler(fd, co_recv_cb)
qemu_coroutine_yield()
aio_set_fd_read_handler(fd, NULL)
continue
return nbytes
The send function is similar.
I see what you mean now---this however is not how qemu_co_recv and
qemu_co_send work. NBD uses them, but they require the caller to set up
the handlers manually.
Paolo
