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

[Luke Browning]

On Fri, 2008-02-15 at 12:35 +0100, Arnd Bergmann wrote:
> 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().

Ok, thanks for the info.

Luke