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@xxxxxxxxxx>
Reviewed-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/locking/qspinlock.c | 38 ++++++++++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 435d696f9250..24b5802fc6f1 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -289,6 +289,34 @@ 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 */
/**
@@ -533,7 +561,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
* 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 */
}
@@ -550,7 +578,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
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:
@@ -575,6 +603,12 @@ 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
--
2.21.1 (Apple Git-122.3)
