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locking/mcs: Better differentiate between MCS variants 

We have two flavors of the MCS spinlock: standard and cancelable (OSQ).
While each one is independent of the other, we currently mix and match
them. This patch:

  - Moves the OSQ code out of mcs_spinlock.h (which only deals with the traditional
    version) into include/linux/osq_lock.h. No unnecessary code is added to the
    more global header file, anything locks that make use of OSQ must include
    it anyway.

  - Renames mcs_spinlock.c to osq_lock.c. This file only contains osq code.

  - Introduces a CONFIG_LOCK_SPIN_ON_OWNER in order to only build osq_lock
    if there is support for it.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1420573509-24774-5-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Davidlohr Bueso 2015-01-06 11:45:07 -08:00 committed by Ingo Molnar
parent 4bd19084fa
commit d84b6728c5
5 changed files with 17 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/osq_lock.h
View File

@ -5,8 +5,11 @@
* An MCS like lock especially tailored for optimistic spinning for sleeping
* lock implementations (mutex, rwsem, etc).
*/
#define OSQ_UNLOCKED_VAL (0)
struct optimistic_spin_node {
struct optimistic_spin_node *next, *prev;
int locked; /* 1 if lock acquired */
int cpu; /* encoded CPU # + 1 value */
};
struct optimistic_spin_queue {
/*
@ -16,6 +19,8 @@ struct optimistic_spin_queue {
atomic_t tail;
};
#define OSQ_UNLOCKED_VAL (0)
/* Init macro and function. */
#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
@ -24,4 +29,7 @@ static inline void osq_lock_init(struct optimistic_spin_queue *lock)
atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
}
extern bool osq_lock(struct optimistic_spin_queue *lock);
extern void osq_unlock(struct optimistic_spin_queue *lock);
#endif

4
kernel/Kconfig.locks
View File

@ -231,6 +231,10 @@ config RWSEM_SPIN_ON_OWNER
def_bool y
depends on SMP && RWSEM_XCHGADD_ALGORITHM && ARCH_SUPPORTS_ATOMIC_RMW
config LOCK_SPIN_ON_OWNER
def_bool y
depends on MUTEX_SPIN_ON_OWNER || RWSEM_SPIN_ON_OWNER
config ARCH_USE_QUEUE_RWLOCK
bool

3
kernel/locking/Makefile
View File

@ -1,5 +1,5 @@
obj-y += mutex.o semaphore.o rwsem.o mcs_spinlock.o
obj-y += mutex.o semaphore.o rwsem.o
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_lockdep.o = -pg
@ -14,6 +14,7 @@ ifeq ($(CONFIG_PROC_FS),y)
obj-$(CONFIG_LOCKDEP) += lockdep_proc.o
endif
obj-$(CONFIG_SMP) += spinlock.o
obj-$(CONFIG_LOCK_SPIN_ON_OWNER) += osq_lock.o
obj-$(CONFIG_SMP) += lglock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_RT_MUTEXES) += rtmutex.o

16
kernel/locking/mcs_spinlock.h
View File

@ -108,20 +108,4 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
arch_mcs_spin_unlock_contended(&next->locked);
}
/*
* Cancellable version of the MCS lock above.
*
* Intended for adaptive spinning of sleeping locks:
* mutex_lock()/rwsem_down_{read,write}() etc.
*/
struct optimistic_spin_node {
struct optimistic_spin_node *next, *prev;
int locked; /* 1 if lock acquired */
int cpu; /* encoded CPU # value */
};
extern bool osq_lock(struct optimistic_spin_queue *lock);
extern void osq_unlock(struct optimistic_spin_queue *lock);
#endif /* __LINUX_MCS_SPINLOCK_H */

7
kernel/locking/mcs_spinlock.c → kernel/locking/osq_lock.c
View File

@ -1,8 +1,6 @@
#include <linux/percpu.h>
#include <linux/sched.h>
#include "mcs_spinlock.h"
#ifdef CONFIG_SMP
#include <linux/osq_lock.h>
/*
* An MCS like lock especially tailored for optimistic spinning for sleeping
@ -203,6 +201,3 @@ void osq_unlock(struct optimistic_spin_queue *lock)
if (next)
ACCESS_ONCE(next->locked) = 1;
}
#endif