[RFC v7 07/21] um: extend arch_switch_to for alternate SUBARCH

[Hajime Tazaki]

On Thu, 08 Oct 2020 00:25:06 +0900,
Johannes Berg wrote:
> 
> On Tue, 2020-10-06 at 18:44 +0900, Hajime Tazaki wrote:
> > This commit introduces additional argument of previous task when
> > context switch happens.  New SUBARCH can use the new information to
> > switch tasks in a subarch-specific manner.
> > 
> > The patch is particularly required by nommu mode implemented as a
> > SUBARCH of UML.
> 
> Would probably be good to already say why here?

Agree.

The patch is particularly required by nommu mode because it uses
previous task information to control the previous thread (e.g., down
semaphore, terminate thread, clean up thread flags).

Something like this ?

-- Hajime