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

[Oleg Nesterov]

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.

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

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

Oleg.

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