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Re: [Xen-devel] [PATCH V3] x86 spinlock: Fix memory corruption on completing completions

On 02/12/2015 07:07 PM, Oleg Nesterov wrote:
On 02/12, 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 = ACCESS_ONCE(lock->tickets.head);
+       if (__tickets_equal(head, want)) {
                add_stats(TAKEN_SLOW_PICKUP, 1);

While at it, perhaps it makes sense to s/ACCESS_ONCE/READ_ONCE/ but this
is cosmetic.

yes.. will do.

We also need to change another user of enter_slow_path, xen_lock_spinning()
in arch/x86/xen/spinlock.c.

Had in mind but forgot before sending. will update resend.

Other than that looks correct at first glance... but this is up to


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