Re: [PATCH 4/6] kvm tools: Add rwlock wrapper

Ingo Molnar
2011-05-27T11:11:07Z

* Ingo Molnar <mingo@elte.hu> wrote:

> I was thinking about that on and off so loudly that Peter
> implemented it long ago via fasync support on the perf event fd!
> :-)
>
> So if you set a notification signal via fcntl(F_SETOWN) on the
> scheduler context switch event fd, the user-space RCU code will get
> a signal on every context switch.
>
> I have not tried it for this purpose yet, so let us know if there
> are unexpected complications :)

Note that you do not want the context switch event, but the CPU
migration event: that will notify user-space when it gets migrated to
another CPU. This is the case that RCU really needs.

Thanks,

Ingo