On Thu, Sep 05, 2019 at 11:12:59PM -0400, Mathieu Desnoyers wrote: > When the prev and next task's mm change, switch_mm() provides the core > serializing guarantees before returning to usermode. The only case > where an explicit core serialization is needed is when the scheduler > keeps the same mm for prev and next. > > Suggested-by: Oleg Nesterov <[email protected]> > Signed-off-by: Mathieu Desnoyers <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Oleg Nesterov <[email protected]> > Cc: "Eric W. Biederman" <[email protected]> > Cc: Linus Torvalds <[email protected]> > Cc: Russell King - ARM Linux admin <[email protected]> > Cc: Chris Metcalf <[email protected]> > Cc: Christoph Lameter <[email protected]> > Cc: Kirill Tkhai <[email protected]> > Cc: Mike Galbraith <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > --- > include/linux/sched/mm.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 4a7944078cc3..8557ec664213 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -362,6 +362,8 @@ enum { > > static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct > *mm) > { > + if (current->mm != mm) > + return; > if (likely(!(atomic_read(&mm->membarrier_state) & > MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE))) > return;
So SYNC_CORE is about I$ coherency and funny thing like that. Now it seems 'natural' that if we flip the address space, that I$ also gets wiped/updated, because the whole text mapping changes. But did we just assume that, or did we verify the truth of this? (I'm just being paranoid here)
