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* [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path
@ 2016-06-01 18:58 Peter Zijlstra
  2016-06-02 13:27 ` Paul E. McKenney
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Peter Zijlstra @ 2016-06-01 18:58 UTC (permalink / raw)
  To: Ingo Molnar, Davidlohr Bueso, Waiman Long, Paul McKenney, viro
  Cc: linux-kernel


A while back Viro posted a number of 'interesting' mutex_is_locked()
users on IRC, one of those was RCU.

RCU seems to use mutex_is_locked() to avoid doing mutex_trylock(), the
regular load before modify pattern.

While the use isn't wrong per se, its curious in that its needed at all,
mutex_trylock() should be good enough on its own to avoid the pointless
cacheline bounces.

So fix those and remove the mutex_is_locked() (ab)use from RCU.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/ia64/include/asm/mutex.h    | 2 +-
 arch/powerpc/include/asm/mutex.h | 2 +-
 arch/x86/include/asm/mutex_32.h  | 2 +-
 arch/x86/include/asm/mutex_64.h  | 6 +++---
 include/asm-generic/mutex-dec.h  | 2 +-
 include/asm-generic/mutex-xchg.h | 6 +++++-
 kernel/rcu/tree.c                | 1 -
 7 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/ia64/include/asm/mutex.h b/arch/ia64/include/asm/mutex.h
index f41e66d65e31..28cb819e0ff9 100644
--- a/arch/ia64/include/asm/mutex.h
+++ b/arch/ia64/include/asm/mutex.h
@@ -82,7 +82,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (cmpxchg_acq(count, 1, 0) == 1)
+	if (atomic_read(count) == 1 && cmpxchg_acq(count, 1, 0) == 1)
 		return 1;
 	return 0;
 }
diff --git a/arch/powerpc/include/asm/mutex.h b/arch/powerpc/include/asm/mutex.h
index 127ab23e1f6c..078155fa1189 100644
--- a/arch/powerpc/include/asm/mutex.h
+++ b/arch/powerpc/include/asm/mutex.h
@@ -124,7 +124,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && __mutex_cmpxchg_lock(count, 1, 0) == 1))
 		return 1;
 	return 0;
 }
diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 85e6cda45a02..e9355a84fc67 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -101,7 +101,7 @@ static inline int __mutex_fastpath_trylock(atomic_t *count,
 					   int (*fail_fn)(atomic_t *))
 {
 	/* cmpxchg because it never induces a false contention state. */
-	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
 		return 1;
 
 	return 0;
diff --git a/arch/x86/include/asm/mutex_64.h b/arch/x86/include/asm/mutex_64.h
index 07537a44216e..d9850758464e 100644
--- a/arch/x86/include/asm/mutex_64.h
+++ b/arch/x86/include/asm/mutex_64.h
@@ -118,10 +118,10 @@ do {								\
 static inline int __mutex_fastpath_trylock(atomic_t *count,
 					   int (*fail_fn)(atomic_t *))
 {
-	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
 		return 1;
-	else
-		return 0;
+
+	return 0;
 }
 
 #endif /* _ASM_X86_MUTEX_64_H */
diff --git a/include/asm-generic/mutex-dec.h b/include/asm-generic/mutex-dec.h
index fd694cfd678a..c54829d3de37 100644
--- a/include/asm-generic/mutex-dec.h
+++ b/include/asm-generic/mutex-dec.h
@@ -80,7 +80,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (likely(atomic_cmpxchg_acquire(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg_acquire(count, 1, 0) == 1))
 		return 1;
 	return 0;
 }
diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
index a6b4a7bd6ac9..3269ec4e195f 100644
--- a/include/asm-generic/mutex-xchg.h
+++ b/include/asm-generic/mutex-xchg.h
@@ -91,8 +91,12 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	int prev = atomic_xchg_acquire(count, 0);
+	int prev;
 
+	if (atomic_read(count) != 1)
+		return 0;
+
+	prev = atomic_xchg_acquire(count, 0);
 	if (unlikely(prev < 0)) {
 		/*
 		 * The lock was marked contended so we must restore that
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c7f1bc4f817c..b7326893221f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3681,7 +3681,6 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 	if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
 	    (rnp == rnp_root ||
 	     ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
-	    !mutex_is_locked(&rsp->exp_mutex) &&
 	    mutex_trylock(&rsp->exp_mutex))
 		goto fastpath;
 

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path
  2016-06-01 18:58 [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path Peter Zijlstra
@ 2016-06-02 13:27 ` Paul E. McKenney
  2016-06-02 14:26 ` Davidlohr Bueso
  2016-06-08 14:26 ` [tip:locking/core] locking/mutex: " tip-bot for Peter Zijlstra
  2 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2016-06-02 13:27 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Ingo Molnar, Davidlohr Bueso, Waiman Long, viro, linux-kernel

On Wed, Jun 01, 2016 at 08:58:15PM +0200, Peter Zijlstra wrote:
> 
> A while back Viro posted a number of 'interesting' mutex_is_locked()
> users on IRC, one of those was RCU.
> 
> RCU seems to use mutex_is_locked() to avoid doing mutex_trylock(), the
> regular load before modify pattern.

Definitely -- the old versions of mutex_trylock() looked to take ownership
of the cacheline, which most definitely is not what you want if you have
a bunch of CPUs doing expedited grace periods concurrently.

> While the use isn't wrong per se, its curious in that its needed at all,
> mutex_trylock() should be good enough on its own to avoid the pointless
> cacheline bounces.
> 
> So fix those and remove the mutex_is_locked() (ab)use from RCU.

Given the changes below that push the mutex_is_locked() check into
mutex_trylock():

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Or I could pull the changes into -rcu if you prefer.

							Thanx, Paul

> Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  arch/ia64/include/asm/mutex.h    | 2 +-
>  arch/powerpc/include/asm/mutex.h | 2 +-
>  arch/x86/include/asm/mutex_32.h  | 2 +-
>  arch/x86/include/asm/mutex_64.h  | 6 +++---
>  include/asm-generic/mutex-dec.h  | 2 +-
>  include/asm-generic/mutex-xchg.h | 6 +++++-
>  kernel/rcu/tree.c                | 1 -
>  7 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/mutex.h b/arch/ia64/include/asm/mutex.h
> index f41e66d65e31..28cb819e0ff9 100644
> --- a/arch/ia64/include/asm/mutex.h
> +++ b/arch/ia64/include/asm/mutex.h
> @@ -82,7 +82,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
>  static inline int
>  __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
>  {
> -	if (cmpxchg_acq(count, 1, 0) == 1)
> +	if (atomic_read(count) == 1 && cmpxchg_acq(count, 1, 0) == 1)
>  		return 1;
>  	return 0;
>  }
> diff --git a/arch/powerpc/include/asm/mutex.h b/arch/powerpc/include/asm/mutex.h
> index 127ab23e1f6c..078155fa1189 100644
> --- a/arch/powerpc/include/asm/mutex.h
> +++ b/arch/powerpc/include/asm/mutex.h
> @@ -124,7 +124,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
>  static inline int
>  __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
>  {
> -	if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
> +	if (likely(atomic_read(count) == 1 && __mutex_cmpxchg_lock(count, 1, 0) == 1))
>  		return 1;
>  	return 0;
>  }
> diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
> index 85e6cda45a02..e9355a84fc67 100644
> --- a/arch/x86/include/asm/mutex_32.h
> +++ b/arch/x86/include/asm/mutex_32.h
> @@ -101,7 +101,7 @@ static inline int __mutex_fastpath_trylock(atomic_t *count,
>  					   int (*fail_fn)(atomic_t *))
>  {
>  	/* cmpxchg because it never induces a false contention state. */
> -	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
> +	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
>  		return 1;
> 
>  	return 0;
> diff --git a/arch/x86/include/asm/mutex_64.h b/arch/x86/include/asm/mutex_64.h
> index 07537a44216e..d9850758464e 100644
> --- a/arch/x86/include/asm/mutex_64.h
> +++ b/arch/x86/include/asm/mutex_64.h
> @@ -118,10 +118,10 @@ do {								\
>  static inline int __mutex_fastpath_trylock(atomic_t *count,
>  					   int (*fail_fn)(atomic_t *))
>  {
> -	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
> +	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
>  		return 1;
> -	else
> -		return 0;
> +
> +	return 0;
>  }
> 
>  #endif /* _ASM_X86_MUTEX_64_H */
> diff --git a/include/asm-generic/mutex-dec.h b/include/asm-generic/mutex-dec.h
> index fd694cfd678a..c54829d3de37 100644
> --- a/include/asm-generic/mutex-dec.h
> +++ b/include/asm-generic/mutex-dec.h
> @@ -80,7 +80,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
>  static inline int
>  __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
>  {
> -	if (likely(atomic_cmpxchg_acquire(count, 1, 0) == 1))
> +	if (likely(atomic_read(count) == 1 && atomic_cmpxchg_acquire(count, 1, 0) == 1))
>  		return 1;
>  	return 0;
>  }
> diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
> index a6b4a7bd6ac9..3269ec4e195f 100644
> --- a/include/asm-generic/mutex-xchg.h
> +++ b/include/asm-generic/mutex-xchg.h
> @@ -91,8 +91,12 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
>  static inline int
>  __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
>  {
> -	int prev = atomic_xchg_acquire(count, 0);
> +	int prev;
> 
> +	if (atomic_read(count) != 1)
> +		return 0;
> +
> +	prev = atomic_xchg_acquire(count, 0);
>  	if (unlikely(prev < 0)) {
>  		/*
>  		 * The lock was marked contended so we must restore that
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c7f1bc4f817c..b7326893221f 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3681,7 +3681,6 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
>  	if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
>  	    (rnp == rnp_root ||
>  	     ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
> -	    !mutex_is_locked(&rsp->exp_mutex) &&
>  	    mutex_trylock(&rsp->exp_mutex))
>  		goto fastpath;
> 
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path
  2016-06-01 18:58 [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path Peter Zijlstra
  2016-06-02 13:27 ` Paul E. McKenney
@ 2016-06-02 14:26 ` Davidlohr Bueso
  2016-06-08 14:26 ` [tip:locking/core] locking/mutex: " tip-bot for Peter Zijlstra
  2 siblings, 0 replies; 4+ messages in thread
From: Davidlohr Bueso @ 2016-06-02 14:26 UTC (permalink / raw)
  To: Peter Zijlstra
  Cc: Ingo Molnar, Waiman Long, Paul McKenney, viro, linux-kernel

On Wed, 01 Jun 2016, Peter Zijlstra wrote:

>
>A while back Viro posted a number of 'interesting' mutex_is_locked()
>users on IRC, one of those was RCU.
>
>RCU seems to use mutex_is_locked() to avoid doing mutex_trylock(), the
>regular load before modify pattern.
>
>While the use isn't wrong per se, its curious in that its needed at all,
>mutex_trylock() should be good enough on its own to avoid the pointless
>cacheline bounces.

Yeah, and we use ccas just about everywhere else for mutexes.

>
>So fix those and remove the mutex_is_locked() (ab)use from RCU.
>
>Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
>Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Acked-by: Davidlohr Bueso <dave@stgolabs.net>

^ permalink raw reply	[flat|nested] 4+ messages in thread
* [tip:locking/core] locking/mutex: Optimize mutex_trylock() fast-path
  2016-06-01 18:58 [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path Peter Zijlstra
  2016-06-02 13:27 ` Paul E. McKenney
  2016-06-02 14:26 ` Davidlohr Bueso
@ 2016-06-08 14:26 ` tip-bot for Peter Zijlstra
  2 siblings, 0 replies; 4+ messages in thread
From: tip-bot for Peter Zijlstra @ 2016-06-08 14:26 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: linux-kernel, dave, viro, Waiman.Long, peterz, akpm, hpa, tglx,
	torvalds, mingo, paulmck

Commit-ID:  6428671bae97caa7040e24e79e969fd87908f4f3
Gitweb:     http://git.kernel.org/tip/6428671bae97caa7040e24e79e969fd87908f4f3
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 1 Jun 2016 20:58:15 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 8 Jun 2016 15:17:01 +0200

locking/mutex: Optimize mutex_trylock() fast-path

A while back Viro posted a number of 'interesting' mutex_is_locked()
users on IRC, one of those was RCU.

RCU seems to use mutex_is_locked() to avoid doing mutex_trylock(), the
regular load before modify pattern.

While the use isn't wrong per se, its curious in that its needed at all,
mutex_trylock() should be good enough on its own to avoid the pointless
cacheline bounces.

So fix those and remove the mutex_is_locked() (ab)use from RCU.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <Waiman.Long@hpe.com>
Link: http://lkml.kernel.org/r/20160601185815.GW3190@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/ia64/include/asm/mutex.h    | 2 +-
 arch/powerpc/include/asm/mutex.h | 2 +-
 arch/x86/include/asm/mutex_32.h  | 2 +-
 arch/x86/include/asm/mutex_64.h  | 6 +++---
 include/asm-generic/mutex-dec.h  | 2 +-
 include/asm-generic/mutex-xchg.h | 6 +++++-
 kernel/rcu/tree.c                | 1 -
 7 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/ia64/include/asm/mutex.h b/arch/ia64/include/asm/mutex.h
index f41e66d..28cb819 100644
--- a/arch/ia64/include/asm/mutex.h
+++ b/arch/ia64/include/asm/mutex.h
@@ -82,7 +82,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (cmpxchg_acq(count, 1, 0) == 1)
+	if (atomic_read(count) == 1 && cmpxchg_acq(count, 1, 0) == 1)
 		return 1;
 	return 0;
 }
diff --git a/arch/powerpc/include/asm/mutex.h b/arch/powerpc/include/asm/mutex.h
index 127ab23..078155f 100644
--- a/arch/powerpc/include/asm/mutex.h
+++ b/arch/powerpc/include/asm/mutex.h
@@ -124,7 +124,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && __mutex_cmpxchg_lock(count, 1, 0) == 1))
 		return 1;
 	return 0;
 }
diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 85e6cda..e9355a8 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -101,7 +101,7 @@ static inline int __mutex_fastpath_trylock(atomic_t *count,
 					   int (*fail_fn)(atomic_t *))
 {
 	/* cmpxchg because it never induces a false contention state. */
-	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
 		return 1;
 
 	return 0;
diff --git a/arch/x86/include/asm/mutex_64.h b/arch/x86/include/asm/mutex_64.h
index 07537a4..d985075 100644
--- a/arch/x86/include/asm/mutex_64.h
+++ b/arch/x86/include/asm/mutex_64.h
@@ -118,10 +118,10 @@ do {								\
 static inline int __mutex_fastpath_trylock(atomic_t *count,
 					   int (*fail_fn)(atomic_t *))
 {
-	if (likely(atomic_cmpxchg(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg(count, 1, 0) == 1))
 		return 1;
-	else
-		return 0;
+
+	return 0;
 }
 
 #endif /* _ASM_X86_MUTEX_64_H */
diff --git a/include/asm-generic/mutex-dec.h b/include/asm-generic/mutex-dec.h
index fd694cf..c54829d 100644
--- a/include/asm-generic/mutex-dec.h
+++ b/include/asm-generic/mutex-dec.h
@@ -80,7 +80,7 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	if (likely(atomic_cmpxchg_acquire(count, 1, 0) == 1))
+	if (likely(atomic_read(count) == 1 && atomic_cmpxchg_acquire(count, 1, 0) == 1))
 		return 1;
 	return 0;
 }
diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
index a6b4a7b..3269ec4 100644
--- a/include/asm-generic/mutex-xchg.h
+++ b/include/asm-generic/mutex-xchg.h
@@ -91,8 +91,12 @@ __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
 static inline int
 __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
 {
-	int prev = atomic_xchg_acquire(count, 0);
+	int prev;
 
+	if (atomic_read(count) != 1)
+		return 0;
+
+	prev = atomic_xchg_acquire(count, 0);
 	if (unlikely(prev < 0)) {
 		/*
 		 * The lock was marked contended so we must restore that
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c7f1bc4..b732689 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3681,7 +3681,6 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 	if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
 	    (rnp == rnp_root ||
 	     ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
-	    !mutex_is_locked(&rsp->exp_mutex) &&
 	    mutex_trylock(&rsp->exp_mutex))
 		goto fastpath;
 

^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2016-06-08 14:27 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-06-01 18:58 [RFC][PATCH] mutex: Optimize mutex_trylock() fast-path Peter Zijlstra
2016-06-02 13:27 ` Paul E. McKenney
2016-06-02 14:26 ` Davidlohr Bueso
2016-06-08 14:26 ` [tip:locking/core] locking/mutex: " tip-bot for Peter Zijlstra

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