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 v3 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Mon, 15 Jul 2019 15:25:33 -0400 [thread overview]
Message-ID: <20190715192536.104548-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20190715192536.104548-1-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 | 40 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 38 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 961781624638..5668466b3006 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -297,6 +297,36 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock,
#define queued_spin_lock_slowpath native_queued_spin_lock_slowpath
#endif
+/*
+ * set_locked_empty_mcs - Try to set the spinlock value to _Q_LOCKED_VAL,
+ * and by doing that unlock the MCS lock when its waiting queue is empty
+ * @lock: Pointer to queued spinlock structure
+ * @val: Current value of the lock
+ * @node: Pointer to the MCS node of the lock holder
+ *
+ * *,*,* -> 0,0,1
+ */
+static __always_inline bool __set_locked_empty_mcs(struct qspinlock *lock,
+ u32 val,
+ struct mcs_spinlock *node)
+{
+ return atomic_try_cmpxchg_relaxed(&lock->val, &val, _Q_LOCKED_VAL);
+}
+
+/*
+ * pass_mcs_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 __pass_mcs_lock(struct mcs_spinlock *node,
+ struct mcs_spinlock *next)
+{
+ arch_mcs_spin_unlock_contended(&next->locked, 1);
+}
+
+#define set_locked_empty_mcs __set_locked_empty_mcs
+#define pass_mcs_lock __pass_mcs_lock
+
#endif /* _GEN_PV_LOCK_SLOWPATH */
/**
@@ -541,7 +571,7 @@ 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 (set_locked_empty_mcs(lock, val, node))
goto release; /* No contention */
}
@@ -558,7 +588,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
if (!next)
next = smp_cond_load_relaxed(&node->next, (VAL));
- arch_mcs_spin_unlock_contended(&next->locked, 1);
+ pass_mcs_lock(node, next);
pv_kick_node(lock, next);
release:
@@ -583,6 +613,12 @@ EXPORT_SYMBOL(queued_spin_lock_slowpath);
#undef pv_kick_node
#undef pv_wait_head_or_lock
+#undef set_locked_empty_mcs
+#define set_locked_empty_mcs __set_locked_empty_mcs
+
+#undef pass_mcs_lock
+#define pass_mcs_lock __pass_mcs_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:[~2019-07-15 19:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 19:25 [PATCH v3 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-07-15 19:25 ` [PATCH v3 1/5] locking/qspinlock: Make arch_mcs_spin_unlock_contended more generic Alex Kogan
2019-07-16 10:23 ` Peter Zijlstra
2019-07-15 19:25 ` Alex Kogan [this message]
2019-07-16 10:20 ` [PATCH v3 2/5] locking/qspinlock: Refactor the qspinlock slow path Peter Zijlstra
2019-07-16 14:53 ` Alex Kogan
2019-07-16 15:58 ` Peter Zijlstra
2019-07-15 19:25 ` [PATCH v3 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-07-15 21:30 ` Waiman Long
2019-07-16 11:04 ` Peter Zijlstra
2019-07-16 14:26 ` Alex Kogan
2019-07-16 14:44 ` Waiman Long
[not found] ` <aa73b86d-902a-bb6f-d372-8645c8299a6d@redhat.com>
[not found] ` <C1C55A40-FDB1-43B5-B551-F9B8BE776DF8@oracle.com>
2019-07-16 14:50 ` Waiman Long
2019-07-17 17:44 ` Alex Kogan
2019-07-17 17:58 ` Waiman Long
2019-07-16 11:05 ` Peter Zijlstra
2019-07-16 14:30 ` Alex Kogan
2019-07-16 15:50 ` Peter Zijlstra
2019-07-16 17:19 ` Alex Kogan
2019-07-16 18:47 ` Peter Zijlstra
2019-07-17 8:39 ` Peter Zijlstra
2019-07-17 8:59 ` Peter Zijlstra
2019-07-17 14:52 ` Alex Kogan
[not found] ` <FFC2D45A-24B3-40E1-ABBB-1D696E830B23@oracle.com>
2019-07-17 15:09 ` Peter Zijlstra
2019-07-17 2:16 ` Waiman Long
2019-07-17 7:44 ` Peter Zijlstra
2019-07-17 13:35 ` Waiman Long
2019-07-17 14:42 ` Alex Kogan
2019-07-15 19:25 ` [PATCH v3 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-07-16 15:59 ` Peter Zijlstra
2019-07-15 19:25 ` [PATCH v3 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2019-07-16 11:47 ` [PATCH v3 0/5] Add NUMA-awareness to qspinlock Nicholas Piggin
[not found] ` <7D29555E-8F72-4EDD-8A87-B1A59C3945A6@oracle.com>
2019-07-16 23:07 ` Nicholas Piggin
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