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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,
	rahul.x.yadav@oracle.com
Subject: [PATCH v6 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Thu,  7 Nov 2019 12:46:19 -0500	[thread overview]
Message-ID: <20191107174622.61718-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20191107174622.61718-1-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>
---
 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 804c0fbd6328..c06d1e8075d9 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -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_pass_lock - 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_pass_lock(struct mcs_spinlock *node,
+					    struct mcs_spinlock *next)
+{
+	arch_mcs_pass_lock(&next->locked, 1);
+}
+
+#define try_clear_tail	__try_clear_tail
+#define mcs_pass_lock		__mcs_pass_lock
+
 #endif /* _GEN_PV_LOCK_SLOWPATH */
 
 /**
@@ -532,7 +560,7 @@ 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 */
 	}
 
@@ -549,7 +577,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 	if (!next)
 		next = smp_cond_load_relaxed(&node->next, (VAL));
 
-	arch_mcs_pass_lock(&next->locked, 1);
+	mcs_pass_lock(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_pass_lock
+#define mcs_pass_lock			__mcs_pass_lock
+
 #undef  queued_spin_lock_slowpath
 #define queued_spin_lock_slowpath	__pv_queued_spin_lock_slowpath
 
-- 
2.11.0 (Apple Git-81)


  parent reply	other threads:[~2019-11-07 17:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 17:46 [PATCH v6 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-11-07 17:46 ` [PATCH v6 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2019-11-07 17:46 ` Alex Kogan [this message]
2019-11-07 17:46 ` [PATCH v6 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-11-10 21:30   ` kbuild test robot
2019-11-14 20:57     ` Alex Kogan
2019-11-15  0:38       ` Luc Van Oostenryck
2019-11-19 14:48   ` [locking/qspinlock] ad3836e30e: will-it-scale.per_thread_ops 73.5% improvement kernel test robot
2019-11-20 15:16   ` [PATCH v6 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock kbuild test robot
2019-11-22 18:28     ` Alex Kogan
2019-11-22 19:29       ` Waiman Long
2019-11-22 19:52         ` Alex Kogan
2019-11-07 17:46 ` [PATCH v6 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-11-07 17:46 ` [PATCH v6 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan

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