linux-kernel - [PATCH v2 5/5] locking/lockdep: Call lock

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Date:   Tue,  2 Oct 2018 16:19:20 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, Waiman Long <longman@...hat.com>
Subject: [PATCH v2 5/5] locking/lockdep: Call lock_release() after releasing the lock

Currently, lock_acquire() is called before acquiring the lock and
lock_release() is called before the releasing the lock. As a result,
the execution time of lock_release() is added to the lock hold time
reducing locking throughput, especially for spinlocks and rwlocks which
tend to have a much shorter lock hold time.

As lock_release() is not going to update any shared data that needs
protection from the lock, we don't actually need to call it before
releasing the lock. So the lock_release() calls are now postponed to
after releasing the lock for spinlocks and rwlocks.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/rwlock_api_smp.h   | 16 ++++++++--------
 include/linux/spinlock_api_smp.h |  8 ++++----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/rwlock_api_smp.h b/include/linux/rwlock_api_smp.h
index 86ebb4bf9c6e..b026940a0962 100644
--- a/include/linux/rwlock_api_smp.h
+++ b/include/linux/rwlock_api_smp.h
@@ -215,63 +215,63 @@ static inline void __raw_write_lock(rwlock_t *lock)
 
 static inline void __raw_write_unlock(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_write_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	preempt_enable();
 }
 
 static inline void __raw_read_unlock(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_read_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	preempt_enable();
 }
 
 static inline void
 __raw_read_unlock_irqrestore(rwlock_t *lock, unsigned long flags)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_read_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_restore(flags);
 	preempt_enable();
 }
 
 static inline void __raw_read_unlock_irq(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_read_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_enable();
 	preempt_enable();
 }
 
 static inline void __raw_read_unlock_bh(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_read_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
 }
 
 static inline void __raw_write_unlock_irqrestore(rwlock_t *lock,
 					     unsigned long flags)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_write_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_restore(flags);
 	preempt_enable();
 }
 
 static inline void __raw_write_unlock_irq(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_write_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_enable();
 	preempt_enable();
 }
 
 static inline void __raw_write_unlock_bh(rwlock_t *lock)
 {
-	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_write_unlock(lock);
+	rwlock_release(&lock->dep_map, 1, _RET_IP_);
 	__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
 }
 
diff --git a/include/linux/spinlock_api_smp.h b/include/linux/spinlock_api_smp.h
index 42dfab89e740..fcb84df0678b 100644
--- a/include/linux/spinlock_api_smp.h
+++ b/include/linux/spinlock_api_smp.h
@@ -147,32 +147,32 @@ static inline void __raw_spin_lock(raw_spinlock_t *lock)
 
 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 {
-	spin_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_spin_unlock(lock);
+	spin_release(&lock->dep_map, 1, _RET_IP_);
 	preempt_enable();
 }
 
 static inline void __raw_spin_unlock_irqrestore(raw_spinlock_t *lock,
 					    unsigned long flags)
 {
-	spin_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_spin_unlock(lock);
+	spin_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_restore(flags);
 	preempt_enable();
 }
 
 static inline void __raw_spin_unlock_irq(raw_spinlock_t *lock)
 {
-	spin_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_spin_unlock(lock);
+	spin_release(&lock->dep_map, 1, _RET_IP_);
 	local_irq_enable();
 	preempt_enable();
 }
 
 static inline void __raw_spin_unlock_bh(raw_spinlock_t *lock)
 {
-	spin_release(&lock->dep_map, 1, _RET_IP_);
 	do_raw_spin_unlock(lock);
+	spin_release(&lock->dep_map, 1, _RET_IP_);
 	__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
 }
 
-- 
2.18.0