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locking/qspinlock: Refactor the qspinlock slow path 

Move some of the code manipulating the spin lock into separate functions.
	This would allow easier integration of alternative ways to manipulate
	that lock.

	Signed-off-by: Alex Kogan <alex.kogan@oracle.com>
	Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
	Reviewed-by: Waiman Long <longman@redhat.com>
This commit is contained in:
Mungerjiang 2021-11-04 14:38:32 +08:00 committed by kaixuxiakx
parent 05e8e4dd54
commit 473f02a34a
1 changed files with 36 additions and 2 deletions
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38
kernel/locking/qspinlock.c
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@ -288,6 +288,34 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock,
#define queued_spin_lock_slowpath native_queued_spin_lock_slowpath
#endif
/*
* __try_clear_tail - try to clear tail by setting the lock value to
* _Q_LOCKED_VAL.
* @lock: Pointer to the queued spinlock structure
* @val: Current value of the lock
* @node: Pointer to the MCS node of the lock holder
*/
static __always_inline bool __try_clear_tail(struct qspinlock *lock,
u32 val,
struct mcs_spinlock *node)
{
return atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL);
}
/*
* __mcs_lock_handoff - pass the MCS lock to the next waiter
* @node: Pointer to the MCS node of the lock holder
* @next: Pointer to the MCS node of the first waiter in the MCS queue
*/
static __always_inline void __mcs_lock_handoff(struct mcs_spinlock *node,
struct mcs_spinlock *next)
{
arch_mcs_lock_handoff(&next->locked, 1);
}
#define try_clear_tail __try_clear_tail
#define mcs_lock_handoff __mcs_lock_handoff
#endif /* _GEN_PV_LOCK_SLOWPATH */
/**
@ -532,7 +560,7 @@ locked:
* PENDING will make the uncontended transition fail.
*/
if ((val & _Q_TAIL_MASK) == tail) {
if (atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL))
if (try_clear_tail(lock, val, node))
goto release; /* No contention */
}
@ -549,7 +577,7 @@ locked:
if (!next)
next = smp_cond_load_relaxed(&node->next, (VAL));
arch_mcs_lock_handoff(&next->locked, 1);
mcs_lock_handoff(node, next);
pv_kick_node(lock, next);
release:
@ -574,6 +602,12 @@ EXPORT_SYMBOL(queued_spin_lock_slowpath);
#undef pv_kick_node
#undef pv_wait_head_or_lock
#undef try_clear_tail
#define try_clear_tail __try_clear_tail
#undef mcs_lock_handoff
#define mcs_lock_handoff __mcs_lock_handoff
#undef queued_spin_lock_slowpath
#define queued_spin_lock_slowpath __pv_queued_spin_lock_slowpath