On Wed, Aug 31, 2016 at 07:28:18AM +1000, Benjamin Herrenschmidt wrote: > It's always been a requirement that if you actually context switch a > full mb() is implied ...
> On powerpc we have a sync deep in _switch to achieve that. OK, fair enough. I must've missed it in the x86 switch_to, must be one of those implied serializing instructions I'm not too familiar with. > (though that isn't the case if you don't actually > switch, ie, you are back to RUNNING before you even hit schedule). Right, which invalidates the claim that schedule() implies a full mb, > This is necessary so that a process who wakes up on a different CPU sees > all of its own load/stores. Don't actually think its needed for that, see the comment from 8643cda549ca4, the scheduler has enough barriers to guarantee Program-Order for tasks without that.
