Re: [patch 5/5] sched: consolidate sbe sbf

[Ingo Molnar <mingo@elte.hu>]

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> We could just do a set_cpus_allowed, or take the lock, 
> set_cpus_allowed, and take the new lock, but that's probably a bit 
> heavy if we can avoid it. In the interests of speed in this fast path, 
> do you think we can do this in sched_fork, before the task has even 
> been put on the tasklist?

yeah, that shouldnt be a problem. Technically we set cpus_allowed up 
under the tasklist lock just to be non-preemptible and to copy the 
parent's _current_ affinity to the child. But sched_fork() is called 
just before and if the parent got its affinity changed between the two 
calls, so what? I'd move all of this code into sched_fork().

> That would avoid all locking problems. Passing clone_flags into 
> sched_fork would not be a problem if we want to distinguish fork() and 
> clone(CLONE_VM).

sure, that was the plan all along with sched_fork() anyway. (i think the 
initial versions had the flag)

> Yes? I'll cut a new patch to do just that.

sure, fine by me.

	Ingo