[Cbe-oss-dev] [PATCH 6/6] spufs: remove run mutex

[Arnd Bergmann]

On Friday 15 February 2008, Luke Browning wrote:
> > 
> > Moreover, your implementation seems to have a bug in that you now prevent
> > one context to be run inside of different threads, which is a feature that
> > people currently use.
> 
> hmm, I was intentionally trying to disallow that case.  With gang
> scheduling, it is somewhat problematic to have the identity of the
> controlling thread changing from instant to instant as the priority of
> the gang is an effective priority that is deduced from the set of
> controlling threads. I wanted to hook the platform specific layer of
> sys_setsched (?) system call to intercept priority changes and apply
> them to the gang.  This makes it much harder.
> 
> Are you sure people are doing this?  Seems like a violation of the
> programming model to me, although unstated at that.

Yes, I'm sure that people are doing this, I remember discussing this
as an obvious way to offload functions to an SPU from a highly threaded
program on the mailing list or on IRC.

It was certainly intended to be used this way, unfortunately we
had to restrict it to threads of a single process, so you can't
use an SPU context across a fork().

	Arnd <><