osq_wait

Name:Get a stable @node->next pointer, either for unlock() or unqueue() purposes.* Can return NULL in case we were the last queued and we updated @lock instead.

Proto:static inline struct optimistic_spin_node *osq_wait_next(struct optimistic_spin_queue *lock, struct optimistic_spin_node *node, struct optimistic_spin_node *prev)

Type:struct optimistic_spin_node

Parameter:

Type	Parameter	Name
struct optimistic_spin_queue *	lock
struct optimistic_spin_node *	node
struct optimistic_spin_node *	prev

struct optimistic_spin_node * next = NULL

curr = We use the value 0 to represent "no CPU", thus the encoded value* will be the CPU number incremented by 1.

old = If prev Then coded CPU # + 1 value Else OSQ_UNLOCKED_VAL

cycle

If atomic_read( & * Stores an encoded value of the CPU # of the tail node in the queue. * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.) == curr && atomic_cmpxchg_acquire( & * Stores an encoded value of the CPU # of the tail node in the queue. * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL., curr, old) == curr Then

Break

If next Then

next = xchg( & next, NULL)

If next Then Break

cpu_relax()

Return next

**Caller**
Name	Describe
osq_lock
osq_unlock

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Function report