On 02/15/2015 09:47 PM, Oleg Nesterov wrote:
Well, I regret I mentioned the lack of barrier after enter_slowpath ;) On 02/15, Raghavendra K T wrote:@@ -46,7 +46,8 @@ static __always_inline bool static_key_false(struct static_key *key); static inline void __ticket_enter_slowpath(arch_spinlock_t *lock) { - set_bit(0, (volatile unsigned long *)&lock->tickets.tail); + set_bit(0, (volatile unsigned long *)&lock->tickets.head); + barrier(); }Because this barrier() looks really confusing. Firsty, it is equally unneeded on x86. At the same time, it can not help. We need a memory barrier() between set_bit(SLOWPATH) and READ_ONCE(head) to avoid the race with spin_unlock(). So I think you should replace it with smp_mb__after_atomic() or remove it.
I resent the patch the above change.
Other than that I believe this version is correct. So I won't insist, this is cosmetic after all.
Thanks Oleg. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
