linux-kernel - [PATCH tip/locking/core 3/3] locking/pvqspinlock: Direct lock stealing count tracking in pv_queued_spin_steal

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Date:	Thu, 10 Dec 2015 15:17:46 -0500
From:	Waiman Long <Waiman.Long@....com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>,
	Waiman Long <Waiman.Long@....com>
Subject: [PATCH tip/locking/core 3/3] locking/pvqspinlock: Direct lock stealing count tracking in pv_queued_spin_steal_lock

This patch moves the lock stealing count tracking code into
pv_queued_spin_steal_lock instead of via a jacket function simplifying
the code.

Signed-off-by: Waiman Long <Waiman.Long@....com>
---
 kernel/locking/qspinlock_paravirt.h |   16 +++++++++-------
 kernel/locking/qspinlock_stat.h     |   13 -------------
 2 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index 72cec9e..21ede57 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -55,6 +55,11 @@ struct pv_node {
 };
 
 /*
+ * Include queued spinlock statistics code
+ */
+#include "qspinlock_stat.h"
+
+/*
  * By replacing the regular queued_spin_trylock() with the function below,
  * it will be called once when a lock waiter enter the PV slowpath before
  * being queued. By allowing one lock stealing attempt here when the pending
@@ -65,9 +70,11 @@ struct pv_node {
 static inline bool pv_queued_spin_steal_lock(struct qspinlock *lock)
 {
 	struct __qspinlock *l = (void *)lock;
+	int ret = !(atomic_read(&lock->val) & _Q_LOCKED_PENDING_MASK) &&
+		   (cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0);
 
-	return !(atomic_read(&lock->val) & _Q_LOCKED_PENDING_MASK) &&
-		(cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0);
+	qstat_inc(qstat_pv_lock_stealing, ret);
+	return ret;
 }
 
 /*
@@ -138,11 +145,6 @@ static __always_inline int trylock_clear_pending(struct qspinlock *lock)
 #endif /* _Q_PENDING_BITS == 8 */
 
 /*
- * Include queued spinlock statistics code
- */
-#include "qspinlock_stat.h"
-
-/*
  * Lock and MCS node addresses hash table for fast lookup
  *
  * Hashing is done on a per-cacheline basis to minimize the need to access
diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
index 283a615..eb2a2c9 100644
--- a/kernel/locking/qspinlock_stat.h
+++ b/kernel/locking/qspinlock_stat.h
@@ -282,19 +282,6 @@ static inline void __pv_wait(u8 *ptr, u8 val)
 #define pv_kick(c)	__pv_kick(c)
 #define pv_wait(p, v)	__pv_wait(p, v)
 
-/*
- * PV unfair trylock count tracking function
- */
-static inline int qstat_spin_steal_lock(struct qspinlock *lock)
-{
-	int ret = pv_queued_spin_steal_lock(lock);
-
-	qstat_inc(qstat_pv_lock_stealing, ret);
-	return ret;
-}
-#undef  queued_spin_trylock
-#define queued_spin_trylock(l)	qstat_spin_steal_lock(l)
-
 #else /* CONFIG_QUEUED_LOCK_STAT */
 
 static inline void qstat_inc(enum qlock_stats stat, bool cond)	{ }
-- 
1.7.1

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