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From: Alex Kogan <alex.kogan@oracle.com>
To: linux@armlinux.org.uk, peterz@infradead.org, mingo@redhat.com,
	will.deacon@arm.com, arnd@arndb.de, longman@redhat.com,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
	hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com,
	jglauber@marvell.com
Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
	alex.kogan@oracle.com, dave.dice@oracle.com
Subject: [PATCH v15 2/6] locking/qspinlock: Refactor the qspinlock slow path
Date: Fri, 14 May 2021 16:07:39 -0400	[thread overview]
Message-ID: <20210514200743.3026725-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20210514200743.3026725-1-alex.kogan@oracle.com>

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>
---
 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..e3518709ffdc 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
 
-- 
2.24.3 (Apple Git-128)


  parent reply	other threads:[~2021-05-14 20:09 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-14 20:07 [PATCH v15 0/6] Add NUMA-awareness to qspinlock Alex Kogan
2021-05-14 20:07 ` [PATCH v15 1/6] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2021-05-14 20:07 ` Alex Kogan [this message]
2021-05-14 20:07 ` [PATCH v15 3/6] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2021-09-22 19:25   ` Davidlohr Bueso
2021-09-22 19:52     ` Waiman Long
2021-09-30 10:05   ` Barry Song
2021-05-14 20:07 ` [PATCH v15 4/6] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2021-05-14 20:07 ` [PATCH v15 5/6] locking/qspinlock: Avoid moving certain threads between waiting queues in CNA Alex Kogan
2021-05-14 20:07 ` [PATCH v15 6/6] locking/qspinlock: Introduce the shuffle reduction optimization into CNA Alex Kogan
2021-09-30  9:44 ` [PATCH v15 0/6] Add NUMA-awareness to qspinlock Barry Song
2021-09-30 16:58   ` Waiman Long
2021-09-30 22:57     ` Barry Song
2021-09-30 23:51   ` Alex Kogan

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