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: alex.kogan@oracle.com, dave.dice@oracle.com,
rahul.x.yadav@oracle.com, steven.sistare@oracle.com,
daniel.m.jordan@oracle.com
Subject: [PATCH v4 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Fri, 6 Sep 2019 10:25:38 -0400 [thread overview]
Message-ID: <20190906142541.34061-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20190906142541.34061-1-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 c3dfcb689400..070015156a10 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)
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next prev parent reply other threads:[~2019-09-06 14:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 14:25 [PATCH v4 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-09-06 14:25 ` [PATCH v4 1/5] locking/qspinlock: Rename arch_mcs_spin_unlock_contended to arch_mcs_pass_lock and make it more generic Alex Kogan
2019-09-17 6:25 ` Hanjun Guo
2019-09-06 14:25 ` Alex Kogan [this message]
2019-09-06 14:25 ` [PATCH v4 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-09-17 17:44 ` Waiman Long
2019-09-19 15:55 ` Alex Kogan
2019-09-19 20:54 ` Waiman Long
2019-09-06 14:25 ` [PATCH v4 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-09-17 18:07 ` Waiman Long
2019-09-06 14:25 ` [PATCH v4 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
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