Re: [Qemu-devel] [PATCH v2 0/5] Fix socket chardev regression

[Peter Xu <peterx@redhat.com>]

On Thu, Aug 23, 2018 at 04:31:20PM +0200, Marc-André Lureau wrote:
> Hi,
> 
> In commit 25679e5d58e "chardev: tcp: postpone async connection setup"
> (and its follow up 99f2f54174a59), Peter moved chardev socket
> connection to machine_done event. However, chardev created later will
> no longer attempt to connect, and chardev created in tests do not have
> machine_done event (breaking some of vhost-user-test).
> 
> The goal was to move the "connect" source to the chardev frontend
> context (the monitor thread context in his case). chr->gcontext is set
> with qemu_chr_fe_set_handlers(). But there is no guarantee that the
> function will be called in general, so we can't delay connection until
> then: the chardev should still attempt to connect during open(), using
> the main context.
> 
> An alternative would be to specify the iothread during chardev
> creation. Setting up monitor OOB would be quite different too, it
> would take the same iothread as argument.
> 
> 99f2f54174a595e is also a bit problematic, since it will behave
> differently before and after machine_done (the first case gives a
> chance to use a different context reliably, the second looks racy)
> 
> In the end, I am not sure this is all necessary, as chardev callbacks
> are called after qemu_chr_fe_set_handlers(), at which point the
> context of sources are updated. In "char-socket: update all ioc
> handlers when changing context", I moved also the hup handler to the
> updated context. So unless the main thread is already stuck, we can
> setup a different context for the chardev at that time. Or not?
> 
> v2:
> - fix a random socket chardev test failure

I have no problem on patch 3-5, but aren't patch 1-2 still breaking
the context switch of chardev?  Or did I misunderstood?

Regards,

-- 
Peter Xu