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 v7 2/5] locking/qspinlock: Refactor the qspinlock slow path
Date: Mon, 25 Nov 2019 16:07:06 -0500 [thread overview]
Message-ID: <20191125210709.10293-3-alex.kogan@oracle.com> (raw)
In-Reply-To: <20191125210709.10293-1-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
--
2.21.0 (Apple Git-122.2)
next prev parent reply other threads:[~2019-11-25 21:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-25 21:07 [PATCH v7 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-11-25 21:07 ` [PATCH v7 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2020-01-22 9:15 ` Peter Zijlstra
[not found] ` <C608A39E-CAFC-4C79-9EB6-3DFD9621E3F6@oracle.com>
2020-01-25 11:23 ` Peter Zijlstra
2019-11-25 21:07 ` Alex Kogan [this message]
2019-11-25 21:07 ` [PATCH v7 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-12-06 17:21 ` Waiman Long
2019-12-06 19:50 ` Alex Kogan
2020-01-21 20:29 ` Peter Zijlstra
2020-01-22 8:58 ` Will Deacon
2020-01-22 9:22 ` Peter Zijlstra
2020-01-22 9:51 ` Peter Zijlstra
2020-01-22 17:04 ` Peter Zijlstra
2020-01-23 9:00 ` Peter Zijlstra
2020-01-30 22:01 ` Alex Kogan
2020-01-31 13:35 ` Peter Zijlstra
2020-01-31 18:33 ` Alex Kogan
2019-11-25 21:07 ` [PATCH v7 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-12-06 18:09 ` Waiman Long
2019-11-25 21:07 ` [PATCH v7 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2019-12-06 22:00 ` Waiman Long
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