On 02/12, Raghavendra K T wrote:
@@ -191,8 +189,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
* We need to check "unlocked" in a loop, tmp.head == head
* can be false positive because of overflow.
- if (tmp.head == (tmp.tail & ~TICKET_SLOWPATH_FLAG) ||
- tmp.head != head)
+ if (__tickets_equal(tmp.head, tmp.tail) || tmp.head != head)
Ah, it seems that "tmp.head != head" should be turned into
Suppose that TICKET_SLOWPATH_FLAG is set after the first ACCESS_ONCE(head),
then tmp.head != head will be true before the first unlock we are waiting
And perhaps you can turn these ACCESS_ONCE into READ_ONCE as well.