[tip:locking/core] locking/mcs: Better differentiate between MCS variants
From: tip-bot for Davidlohr Bueso
Date: Wed Jan 14 2015 - 14:20:38 EST
Commit-ID: d84b6728c54dcf73bcef3e3f7cf6767e2d224e39
Gitweb: http://git.kernel.org/tip/d84b6728c54dcf73bcef3e3f7cf6767e2d224e39
Author: Davidlohr Bueso <dave@xxxxxxxxxxxx>
AuthorDate: Tue, 6 Jan 2015 11:45:07 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 14 Jan 2015 15:07:32 +0100
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@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Jason Low <jason.low2@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Waiman Long <Waiman.Long@xxxxxx>
Link: http://lkml.kernel.org/r/1420573509-24774-5-git-send-email-dave@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
include/linux/osq_lock.h | 12 ++++++++++--
kernel/Kconfig.locks | 4 ++++
kernel/locking/Makefile | 3 ++-
kernel/locking/mcs_spinlock.h | 16 ----------------
kernel/locking/{mcs_spinlock.c => osq_lock.c} | 7 +------
5 files changed, 17 insertions(+), 25 deletions(-)
diff --git a/include/linux/osq_lock.h b/include/linux/osq_lock.h
index 90230d5..3a6490e 100644
--- a/include/linux/osq_lock.h
+++ b/include/linux/osq_lock.h
@@ -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
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index 76768ee..08561f1 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -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
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 8541bfd..4ca8eb1 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -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
diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h
index 4d60986..d1fe2ba 100644
--- a/kernel/locking/mcs_spinlock.h
+++ b/kernel/locking/mcs_spinlock.h
@@ -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 */
diff --git a/kernel/locking/mcs_spinlock.c b/kernel/locking/osq_lock.c
similarity index 98%
rename from kernel/locking/mcs_spinlock.c
rename to kernel/locking/osq_lock.c
index 9887a90..ec83d4d 100644
--- a/kernel/locking/mcs_spinlock.c
+++ b/kernel/locking/osq_lock.c
@@ -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
-
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/