* [PATCH-queue/locking/core] locking/mutex: Unify yield_to_waiter & waiter_spinning
@ 2016-08-19 1:15 Waiman Long
2016-08-19 1:28 ` Jason Low
0 siblings, 1 reply; 3+ messages in thread
From: Waiman Long @ 2016-08-19 1:15 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: linux-kernel, Linus Torvalds, Ding Tianhong, Jason Low,
Davidlohr Bueso, Paul E. McKenney, Thomas Gleixner, Will Deacon,
Tim Chen, Imre Deak, Waiman Long
Both waiter_spinning and yield_to_waiter are used for somewhat similar
purpose. The waiter_spinning flag is used in CONFIG_MUTEX_SPIN_ON_OWNER
to make optimistic spinner yield to spinning waiter; whereas the
yield_to_waiter is used in !CONFIG_MUTEX_SPIN_ON_OWNER to make new
incoming mutex locker to yield to the sleeping waiter.
This patch unifies these 2 flags into a single yield_to_waiter
flag that is used in both CONFIG_MUTEX_SPIN_ON_OWNER and
!CONFIG_MUTEX_SPIN_ON_OWNER codes.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
---
include/linux/mutex.h | 8 ++++++--
kernel/locking/mutex.c | 12 ++++++------
2 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 988c020..2b3dcdb 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -57,8 +57,12 @@ struct mutex {
#endif
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
struct optimistic_spin_queue osq; /* Spinner MCS lock */
- int waiter_spinning;
-#elif defined(CONFIG_SMP)
+#endif
+#ifdef CONFIG_SMP
+ /*
+ * Used by both CONFIG_MUTEX_SPIN_ON_OWNER (depends on CONFIG_SMP) &
+ * !CONFIG_MUTEX_SPIN_ON_OWNER codes.
+ */
int yield_to_waiter;
#endif
#ifdef CONFIG_DEBUG_MUTEXES
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index c4261fa..7218835 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -55,8 +55,8 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
mutex_clear_owner(lock);
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
osq_lock_init(&lock->osq);
- lock->waiter_spinning = false;
-#elif defined(CONFIG_SMP)
+#endif
+#ifdef CONFIG_SMP
lock->yield_to_waiter = false;
#endif
@@ -351,7 +351,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
* Turn on the waiter spinning flag to discourage the spinner
* from getting the lock.
*/
- lock->waiter_spinning = true;
+ lock->yield_to_waiter = true;
}
for (;;) {
@@ -374,11 +374,11 @@ static bool mutex_optimistic_spin(struct mutex *lock,
}
/*
- * For regular opt-spinner, it waits until the waiter_spinning
+ * For regular opt-spinner, it waits until the yield_to_waiter
* flag isn't set. This will ensure forward progress for
* the waiter spinner.
*/
- if (!waiter && READ_ONCE(lock->waiter_spinning)) {
+ if (!waiter && READ_ONCE(lock->yield_to_waiter)) {
if (need_resched())
break;
goto relax;
@@ -430,7 +430,7 @@ relax:
if (!waiter)
osq_unlock(&lock->osq);
else
- lock->waiter_spinning = false;
+ lock->yield_to_waiter = false;
done:
/*
* If we fell out of the spin path because of need_resched(),
--
1.7.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH-queue/locking/core] locking/mutex: Unify yield_to_waiter & waiter_spinning
2016-08-19 1:15 [PATCH-queue/locking/core] locking/mutex: Unify yield_to_waiter & waiter_spinning Waiman Long
@ 2016-08-19 1:28 ` Jason Low
2016-08-19 15:25 ` Waiman Long
0 siblings, 1 reply; 3+ messages in thread
From: Jason Low @ 2016-08-19 1:28 UTC (permalink / raw)
To: Waiman Long
Cc: jason.low2, Peter Zijlstra, Ingo Molnar, linux-kernel,
Linus Torvalds, Ding Tianhong, Davidlohr Bueso, Paul E. McKenney,
Thomas Gleixner, Will Deacon, Tim Chen, Imre Deak, jason.low2
On Thu, 2016-08-18 at 21:15 -0400, Waiman Long wrote:
> Both waiter_spinning and yield_to_waiter are used for somewhat similar
> purpose. The waiter_spinning flag is used in CONFIG_MUTEX_SPIN_ON_OWNER
> to make optimistic spinner yield to spinning waiter; whereas the
> yield_to_waiter is used in !CONFIG_MUTEX_SPIN_ON_OWNER to make new
> incoming mutex locker to yield to the sleeping waiter.
>
> This patch unifies these 2 flags into a single yield_to_waiter
> flag that is used in both CONFIG_MUTEX_SPIN_ON_OWNER and
> !CONFIG_MUTEX_SPIN_ON_OWNER codes.
>
> Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
> ---
> include/linux/mutex.h | 8 ++++++--
> kernel/locking/mutex.c | 12 ++++++------
> 2 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 988c020..2b3dcdb 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -57,8 +57,12 @@ struct mutex {
> #endif
> #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
> struct optimistic_spin_queue osq; /* Spinner MCS lock */
> - int waiter_spinning;
> -#elif defined(CONFIG_SMP)
> +#endif
> +#ifdef CONFIG_SMP
> + /*
> + * Used by both CONFIG_MUTEX_SPIN_ON_OWNER (depends on CONFIG_SMP) &
> + * !CONFIG_MUTEX_SPIN_ON_OWNER codes.
> + */
> int yield_to_waiter;
> #endif
> #ifdef CONFIG_DEBUG_MUTEXES
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index c4261fa..7218835 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -55,8 +55,8 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
> mutex_clear_owner(lock);
> #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
> osq_lock_init(&lock->osq);
> - lock->waiter_spinning = false;
> -#elif defined(CONFIG_SMP)
> +#endif
> +#ifdef CONFIG_SMP
> lock->yield_to_waiter = false;
> #endif
>
> @@ -351,7 +351,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
> * Turn on the waiter spinning flag to discourage the spinner
> * from getting the lock.
Might want to update this comment to "Turn on the yield to waiter flag
to discourage optimistic spinners from stealing the lock."
Besides that:
Acked-by: Jason Low <jason.low2@hpe.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH-queue/locking/core] locking/mutex: Unify yield_to_waiter & waiter_spinning
2016-08-19 1:28 ` Jason Low
@ 2016-08-19 15:25 ` Waiman Long
0 siblings, 0 replies; 3+ messages in thread
From: Waiman Long @ 2016-08-19 15:25 UTC (permalink / raw)
To: Jason Low
Cc: Peter Zijlstra, Ingo Molnar, linux-kernel, Linus Torvalds,
Ding Tianhong, Davidlohr Bueso, Paul E. McKenney, Thomas Gleixner,
Will Deacon, Tim Chen, Imre Deak, jason.low2
On 08/18/2016 09:28 PM, Jason Low wrote:
> On Thu, 2016-08-18 at 21:15 -0400, Waiman Long wrote:
>> Both waiter_spinning and yield_to_waiter are used for somewhat similar
>> purpose. The waiter_spinning flag is used in CONFIG_MUTEX_SPIN_ON_OWNER
>> to make optimistic spinner yield to spinning waiter; whereas the
>> yield_to_waiter is used in !CONFIG_MUTEX_SPIN_ON_OWNER to make new
>> incoming mutex locker to yield to the sleeping waiter.
>>
>> This patch unifies these 2 flags into a single yield_to_waiter
>> flag that is used in both CONFIG_MUTEX_SPIN_ON_OWNER and
>> !CONFIG_MUTEX_SPIN_ON_OWNER codes.
>>
>> Signed-off-by: Waiman Long<Waiman.Long@hpe.com>
>> ---
>> include/linux/mutex.h | 8 ++++++--
>> kernel/locking/mutex.c | 12 ++++++------
>> 2 files changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
>> index 988c020..2b3dcdb 100644
>> --- a/include/linux/mutex.h
>> +++ b/include/linux/mutex.h
>> @@ -57,8 +57,12 @@ struct mutex {
>> #endif
>> #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
>> struct optimistic_spin_queue osq; /* Spinner MCS lock */
>> - int waiter_spinning;
>> -#elif defined(CONFIG_SMP)
>> +#endif
>> +#ifdef CONFIG_SMP
>> + /*
>> + * Used by both CONFIG_MUTEX_SPIN_ON_OWNER (depends on CONFIG_SMP)&
>> + * !CONFIG_MUTEX_SPIN_ON_OWNER codes.
>> + */
>> int yield_to_waiter;
>> #endif
>> #ifdef CONFIG_DEBUG_MUTEXES
>> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
>> index c4261fa..7218835 100644
>> --- a/kernel/locking/mutex.c
>> +++ b/kernel/locking/mutex.c
>> @@ -55,8 +55,8 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
>> mutex_clear_owner(lock);
>> #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
>> osq_lock_init(&lock->osq);
>> - lock->waiter_spinning = false;
>> -#elif defined(CONFIG_SMP)
>> +#endif
>> +#ifdef CONFIG_SMP
>> lock->yield_to_waiter = false;
>> #endif
>>
>> @@ -351,7 +351,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
>> * Turn on the waiter spinning flag to discourage the spinner
>> * from getting the lock.
> Might want to update this comment to "Turn on the yield to waiter flag
> to discourage optimistic spinners from stealing the lock."
>
> Besides that:
>
> Acked-by: Jason Low<jason.low2@hpe.com>
>
You are right. I should have made that comment change. As you have a new
patch outstanding, I will wait a bit until it stabilizes before I update
my patch.
Cheers,
Longman
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-08-19 1:15 [PATCH-queue/locking/core] locking/mutex: Unify yield_to_waiter & waiter_spinning Waiman Long
2016-08-19 1:28 ` Jason Low
2016-08-19 15:25 ` Waiman Long
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