Restructure code to allow for architecture specific defines
of the arch_mcs_spin_lock and arch_mcs_spin_unlock funtion
that can be optimized for specific architecture. These
arch specific functions can be placed in asm/mcs_spinlock.h.
Otherwise the default arch_mcs_spin_lock and arch_mcs_spin_unlock
will be used.
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
arch/Kconfig | 3 ++
include/linux/mcs_spinlock.h | 5 +++
kernel/locking/mcs_spinlock.c | 93 +++++++++++++++++++++++++------------------
3 files changed, 62 insertions(+), 39 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index ded747c..c96c696 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -306,6 +306,9 @@ config HAVE_CMPXCHG_LOCAL
config HAVE_CMPXCHG_DOUBLE
bool
+config HAVE_ARCH_MCS_LOCK
+ bool
+
config ARCH_WANT_IPC_PARSE_VERSION
bool
diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h
index d54bb23..d64786a 100644
--- a/include/linux/mcs_spinlock.h
+++ b/include/linux/mcs_spinlock.h
@@ -12,6 +12,11 @@
#ifndef __LINUX_MCS_SPINLOCK_H
#define __LINUX_MCS_SPINLOCK_H
+/* arch specific mcs lock and unlock functions defined here */
+#ifdef CONFIG_HAVE_ARCH_MCS_LOCK
+#include <asm/mcs_spinlock.h>
+#endif
+
struct mcs_spinlock {
struct mcs_spinlock *next;
int locked; /* 1 if lock acquired */
diff --git a/kernel/locking/mcs_spinlock.c b/kernel/locking/mcs_spinlock.c
index 6f2ce8e..582584a 100644
--- a/kernel/locking/mcs_spinlock.c
+++ b/kernel/locking/mcs_spinlock.c
@@ -29,28 +29,36 @@
* on this node->locked until the previous lock holder sets the node->locked
* in mcs_spin_unlock().
*/
+#ifndef arch_mcs_spin_lock
+#define arch_mcs_spin_lock(lock, node) \
+{ \
+ struct mcs_spinlock *prev; \
+ \
+ /* Init node */ \
+ node->locked = 0; \
+ node->next = NULL; \
+ \
+ /* xchg() provides a memory barrier */ \
+ prev = xchg(lock, node); \
+ if (likely(prev == NULL)) { \
+ /* Lock acquired */ \
+ return; \
+ } \
+ ACCESS_ONCE(prev->next) = node; \
+ /* \
+ * Wait until the lock holder passes the lock down. \
+ * Using smp_load_acquire() provides a memory barrier that \
+ * ensures subsequent operations happen after the lock is \
+ * acquired. \
+ */ \
+ while (!(smp_load_acquire(&node->locked))) \
+ arch_mutex_cpu_relax(); \
+}
+#endif
+
void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
{
- struct mcs_spinlock *prev;
-
- /* Init node */
- node->locked = 0;
- node->next = NULL;
-
- /* xchg() provides a memory barrier */
- prev = xchg(lock, node);
- if (likely(prev == NULL)) {
- /* Lock acquired */
- return;
- }
- ACCESS_ONCE(prev->next) = node;
- /*
- * Wait until the lock holder passes the lock down.
- * Using smp_load_acquire() provides a memory barrier that
- * ensures subsequent operations happen after the lock is acquired.
- */
- while (!(smp_load_acquire(&node->locked)))
- arch_mutex_cpu_relax();
+ arch_mcs_spin_lock(lock, node);
}
EXPORT_SYMBOL_GPL(mcs_spin_lock);
@@ -58,26 +66,33 @@ EXPORT_SYMBOL_GPL(mcs_spin_lock);
* Releases the lock. The caller should pass in the corresponding node that
* was used to acquire the lock.
*/
+#ifndef arch_mcs_spin_unlock
+#define arch_mcs_spin_unlock(lock, 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(); \
+ } \
+ /* \
+ * Pass lock to next waiter. \
+ * smp_store_release() provides a memory barrier to ensure \
+ * all operations in the critical section has been completed \
+ * before unlocking. \
+ */ \
+ smp_store_release(&next->locked, 1); \
+}
+#endif
+
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();
- }
- /*
- * Pass lock to next waiter.
- * smp_store_release() provides a memory barrier to ensure
- * all operations in the critical section has been completed
- * before unlocking.
- */
- smp_store_release(&next->locked, 1);
+ arch_mcs_spin_unlock(lock, node);
}
EXPORT_SYMBOL_GPL(mcs_spin_unlock);
--
1.7.11.7
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