Re: [PATCH] Use deltas to replace atomic inc

[Christoph Lameter <clameter@engr.sgi.com>]

On Sat, 20 Aug 2005, Andrew Morton wrote:

> Christoph Lameter <clameter@engr.sgi.com> wrote:
> >
> >  @@ -508,6 +508,16 @@ static int unuse_mm(struct mm_struct *mm
> >   {
> >   	struct vm_area_struct *vma;
> >   
> >  +	/*
> >  +	 * Ensure that existing deltas are charged to the current mm since
> >  +	 * we will charge the next batch manually to the target mm
> >  +	 */
> >  +	if (current->mm && mm_counter_updates_pending(current)) {
> 
> Is there a race window right here?

Why? current is tied to a thread.

The thing that bothers me more is that schedule() can be called both by 
handle_mm_fault as well as during unuse_mm. We may need some flag 
PF_NO_COUNTER_UPDATES or so there to insure that schedule() does not add 
deltas to the current->mm.
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