Re: [Xen-devel] [PATCH V4] x86 spinlock: Fix memory corruption on completing completions

[Oleg Nesterov <oleg@xxxxxxxxxx>]

On 02/13, Oleg Nesterov wrote:
>
> On 02/13, Raghavendra K T wrote:
> >
> > @@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock 
> > *lock, __ticket_t want)
> >      * check again make sure it didn't become free while
> >      * we weren't looking.
> >      */
> > -   if (ACCESS_ONCE(lock->tickets.head) == want) {
> > +   head = READ_ONCE(lock->tickets.head);
> > +   if (__tickets_equal(head, want)) {
> >             add_stats(TAKEN_SLOW_PICKUP, 1);
> >             goto out;
>
> This is off-topic, but with or without this change perhaps it makes sense
> to add smp_mb__after_atomic(). It is nop on x86, just to make this code
> more understandable for those (for me ;) who can never remember even the
> x86 rules.

Not that I think you should do this in v5, so please ignore.

Oleg.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel