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

[Luke Browning]

On Wed, 2008-02-13 at 06:03 +0100, Arnd Bergmann wrote:

> AFAICS, this return value gets propagated to user space, in the place where
> we would formerly block. This is an ABI change that should be thought through
> carefully!

yes.

> 
> 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.

> 
> Also, you would at least need to document the new interface in the spu_run
> man page and check if there are any ABI relevant implications to the libspe
> interface.

yes, that was coming.

Regards,
Luke