On Thu, 11/30 17:04, Paolo Bonzini wrote: > On 30/11/2017 16:10, Kevin Wolf wrote: > >> Yes, I agree, but that (using CoMutex around graph change) requires > >> everything, especially the defer_to_main_loop_bh, runs in a coroutine > >> context, which is exactly what I mean by "introducing 'ubiquitous > >> coroutines'", because currently we don't have them. > > Is it hard to do, though? Instead of using a BH to switch to the main > > loop and outside of coroutine context, you could use aio_co_schedule() > > and yield, which would leave you in the main loop, but still in > > coroutine context. > > Not that I think of, but just aio_co_schedule wouldn't work, because > "the coroutine must have yielded unless ctx is the context in which the > coroutine is running (i.e. the value of qemu_get_current_aio_context() > from the coroutine itself)". > > So you'd have to use a bottom half that calls aio_co_schedule. But that > would work. >
We have QMP commands that can manupulate the graph which are all not coroutines. I think running QMP commands in coroutines has it merit especially regarding to the nested event loops. Also the bdrv_close_all() and similar at the end of main() do draining too, which I'm not sure how to deal with. Maybe special case them and forget the draining CoMutex? Fam
