Re: freezing of kernel threads

[Keir Fraser <keir.xen@gmail.com>]

On 22/11/2012 11:21, "Jan Beulich" <JBeulich@suse.com> wrote:

> Keir,
> 
> in linux-2.6.18-xen.hg c/s 74:cb50d25a9468 you made blktap
> match blkback in calling try_to_freeze() from the main thread loop.
> Threads in other drivers didn't get changed, though. Is there a
> particular reason why only block, and only backend, threads are in
> need of this (the only other one using it is xenfb_thread())?

I don't really recall. I expect someone pointed out the difference between
the two drivers and so I added the call to blktap. Back then I don't know
that any of our other drivers had kthreads?

 -- Keir

> Konrad, as of 2.6.23 kernel threads are non-freezable by default,
> i.e. xen-blkback calling try_to_freeze() is completely pointless
> without a prior call to set_freezable(). Also, in case the latter is to
> be added, switching to wait_event_freezable() instead of the
> direct use of try_to_freeze() might be the right way to go.
> 
> Jan
>