> From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Sent: Tuesday, October 8, 2019 6:00 AM
> ...
> > Looking at the uses of VERSION_INVAL, I find one remaining occurrence
> > of this macro in vmbus_bus_resume(), which does:
> >
> > if (vmbus_proto_version == VERSION_INVAL ||
> > vmbus_proto_version == 0) {
> > ...
> > }
> >
> > TBH I'm looking at vmbus_bus_resume() and vmbus_bus_suspend() for the
> > first time and I'm not sure about how to change such check yet... any
> > suggestions?
>
> Hm, I don't think vmbus_proto_version can ever become == VERSION_INVAL
> if we rewrite the code the way you suggest, right? So you'll reduce this
> to 'if (!vmbus_proto_version)' meaning we haven't negotiated any version
> (yet).
Yeah, Vitaly is correct. The check may be a little paranoid as I believe
"vmbus_proto_version" must be a negotiated value in vmbus_bus_resume()
and vmbus_bus_suspend(). I added the check just in case.
> > Mmh, I see that vmbus_bus_resume() and vmbus_bus_suspend() can access
> > vmbus_connection.conn_state: can such accesses race with a concurrent
> > vmbus_connect()?
>
> Let's summon Dexuan who's the author! :-)
There should not be an issue:
vmbus_connect() is called in the early subsys_initcall(hv_acpi_init).
vmbus_bus_suspend() is called late in the PM code after the kernel boots up, e.g.
in the hibernation function hibernation_snapshot() -> dpm_suspend().
vmbus_bus_resume() is also called later in late_initcall_sync(software_resume).
In the hibernatin process, vmbus_bus_suspend()/resume() can also be called a
few times, and vmbus_bus_resume() calls vmbus_negotiate_version(). As I
checked, there is no issue, either.
Thanks,
Dexuan
