Am 11.07.2019 um 21:58 hat Max Reitz geschrieben: > When nbd_close() is called from a coroutine, the connection_co never > gets to run, and thus nbd_teardown_connection() hangs. > > This is because aio_co_enter() only puts the connection_co into the main > coroutine's wake-up queue, so this main coroutine needs to yield and > reschedule itself to let the connection_co run. > > Signed-off-by: Max Reitz <mre...@redhat.com> > --- > block/nbd.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/block/nbd.c b/block/nbd.c > index 81edabbf35..b83b6cd43e 100644 > --- a/block/nbd.c > +++ b/block/nbd.c > @@ -135,7 +135,17 @@ static void nbd_teardown_connection(BlockDriverState *bs) > qio_channel_shutdown(s->ioc, > QIO_CHANNEL_SHUTDOWN_BOTH, > NULL); > - BDRV_POLL_WHILE(bs, s->connection_co); > + > + if (qemu_in_coroutine()) { > + /* Let our caller poll and just yield until connection_co is done */ > + while (s->connection_co) { > + aio_co_schedule(qemu_get_current_aio_context(), > + qemu_coroutine_self()); > + qemu_coroutine_yield(); > + }
Isn't this busy waiting? Why not let s->connection_co wake us up when it's about to terminate instead of immediately rescheduling ourselves? > + } else { > + BDRV_POLL_WHILE(bs, s->connection_co); > + } > > nbd_client_detach_aio_context(bs); > object_unref(OBJECT(s->sioc)); Kevin