From: Waiman Long <Waiman.Long@xxxxxx>
The following changes are made:
1) Create a new mcs_spinlock.c file to contain the
mcs_spin_lock() and mcs_spin_unlock() function.
2) Include a number of prerequisite header files and define
arch_mutex_cpu_relax(), if not previously defined so the
mcs functions can be compiled for multiple architecture without
causing problems.
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
include/linux/mcs_spinlock.h | 56 ++------------------
kernel/locking/Makefile | 6 +-
.../locking/mcs_spinlock.c | 31 ++++++-----
3 files changed, 23 insertions(+), 70 deletions(-)
copy include/linux/mcs_spinlock.h => kernel/locking/mcs_spinlock.c (78%)
diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h
index 96f14299..d54bb23 100644
--- a/include/linux/mcs_spinlock.h
+++ b/include/linux/mcs_spinlock.h
@@ -17,57 +17,9 @@ struct mcs_spinlock {
int locked; /* 1 if lock acquired */
};
-/*
- * In order to acquire the lock, the caller should declare a local node and
- * pass a reference of the node to this function in addition to the lock.
- * If the lock has already been acquired, then this will proceed to spin
- * on this node->locked until the previous lock holder sets the node->locked
- * in mcs_spin_unlock().
- *
- * We don't inline mcs_spin_lock() so that perf can correctly account for the
- * time spent in this lock function.
- */
-static noinline
-void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
-{
- struct mcs_spinlock *prev;
-
- /* Init node */
- node->locked = 0;
- node->next = NULL;
-
- prev = xchg(lock, node);
- if (likely(prev == NULL)) {
- /* Lock acquired */
- return;
- }
- ACCESS_ONCE(prev->next) = node;
- smp_wmb();
- /* Wait until the lock holder passes the lock down */
- while (!ACCESS_ONCE(node->locked))
- arch_mutex_cpu_relax();
-}
-
-/*
- * Releases the lock. The caller should pass in the corresponding node that
- * was used to acquire the lock.
- */
-static void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
-{
- struct mcs_spinlock *next = ACCESS_ONCE(node->next);
-
- if (likely(!next)) {
- /*
- * Release the lock by setting it to NULL
- */
- if (likely(cmpxchg(lock, node, NULL) == node))
- return;
- /* Wait until the next pointer is set */
- while (!(next = ACCESS_ONCE(node->next)))
- arch_mutex_cpu_relax();
- }
- ACCESS_ONCE(next->locked) = 1;
- smp_wmb();
-}
+extern
+void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node);
+extern
+void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node);
#endif /* __LINUX_MCS_SPINLOCK_H */
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index baab8e5..20d9d5c 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -13,12 +13,12 @@ obj-$(CONFIG_LOCKDEP) += lockdep.o
ifeq ($(CONFIG_PROC_FS),y)
obj-$(CONFIG_LOCKDEP) += lockdep_proc.o
endif
-obj-$(CONFIG_SMP) += spinlock.o
-obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
+obj-$(CONFIG_SMP) += spinlock.o mcs_spinlock.o
+obj-$(CONFIG_PROVE_LOCKING) += spinlock.o mcs_spinlock.o
obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
-obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
+obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o mcs_spinlock.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
obj-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
obj-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem-xadd.o
diff --git a/include/linux/mcs_spinlock.h b/kernel/locking/mcs_spinlock.c
similarity index 78%
copy from include/linux/mcs_spinlock.h
copy to kernel/locking/mcs_spinlock.c
index 96f14299..b6f27f8 100644
--- a/include/linux/mcs_spinlock.h
+++ b/kernel/locking/mcs_spinlock.c
@@ -1,7 +1,5 @@
/*
- * MCS lock defines
- *
- * This file contains the main data structure and API definitions of MCS lock.
+ * MCS lock
*
* The MCS lock (proposed by Mellor-Crummey and Scott) is a simple spin-lock
* with the desirable properties of being fair, and with each cpu trying
@@ -9,13 +7,20 @@
* It avoids expensive cache bouncings that common test-and-set spin-lock
* implementations incur.
*/
-#ifndef __LINUX_MCS_SPINLOCK_H
-#define __LINUX_MCS_SPINLOCK_H
+/*
+ * asm/processor.h may define arch_mutex_cpu_relax().
+ * If it is not defined, cpu_relax() will be used.
+ */
+#include <asm/barrier.h>
+#include <asm/cmpxchg.h>
+#include <asm/processor.h>
+#include <linux/compiler.h>
+#include <linux/mcs_spinlock.h>
+#include <linux/export.h>
-struct mcs_spinlock {
- struct mcs_spinlock *next;
- int locked; /* 1 if lock acquired */
-};
+#ifndef arch_mutex_cpu_relax
+# define arch_mutex_cpu_relax() cpu_relax()
+#endif
/*
* In order to acquire the lock, the caller should declare a local node and
@@ -23,11 +28,7 @@ struct mcs_spinlock {
* If the lock has already been acquired, then this will proceed to spin
* on this node->locked until the previous lock holder sets the node->locked
* in mcs_spin_unlock().
- *
- * We don't inline mcs_spin_lock() so that perf can correctly account for the
- * time spent in this lock function.
*/
-static noinline
void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
{
struct mcs_spinlock *prev;
@@ -47,6 +48,7 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
while (!ACCESS_ONCE(node->locked))
arch_mutex_cpu_relax();
}
+EXPORT_SYMBOL_GPL(mcs_spin_lock);
/*
* Releases the lock. The caller should pass in the corresponding node that
@@ -69,5 +71,4 @@ static void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *nod
ACCESS_ONCE(next->locked) = 1;
smp_wmb();
}
-
-#endif /* __LINUX_MCS_SPINLOCK_H */
+EXPORT_SYMBOL_GPL(mcs_spin_unlock);
--
1.7.4.4
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