+++ /dev/null
-/*
- * MCS lock defines
- *
- * This file contains the main data structure and API definitions of 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
- * to acquire the lock spinning on a local variable.
- * It avoids expensive cache bouncings that common test-and-set spin-lock
- * implementations incur.
- */
-#ifndef __LINUX_MCS_SPINLOCK_H
-#define __LINUX_MCS_SPINLOCK_H
-
-#include <asm/mcs_spinlock.h>
-
-struct mcs_spinlock {
- struct mcs_spinlock *next;
- int locked; /* 1 if lock acquired */
-};
-
-#ifndef arch_mcs_spin_lock_contended
-/*
- * Using smp_load_acquire() provides a memory barrier that ensures
- * subsequent operations happen after the lock is acquired.
- */
-#define arch_mcs_spin_lock_contended(l) \
-do { \
- while (!(smp_load_acquire(l))) \
- arch_mutex_cpu_relax(); \
-} while (0)
-#endif
-
-#ifndef arch_mcs_spin_unlock_contended
-/*
- * smp_store_release() provides a memory barrier to ensure all
- * operations in the critical section has been completed before
- * unlocking.
- */
-#define arch_mcs_spin_unlock_contended(l) \
- smp_store_release((l), 1)
-#endif
-
-/*
- * Note: the smp_load_acquire/smp_store_release pair is not
- * sufficient to form a full memory barrier across
- * cpus for many architectures (except x86) for mcs_unlock and mcs_lock.
- * For applications that need a full barrier across multiple cpus
- * with mcs_unlock and mcs_lock pair, smp_mb__after_unlock_lock() should be
- * used after mcs_lock.
- */
-
-/*
- * 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 inline
-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, don't need to set node->locked to 1. Threads
- * only spin on its own node->locked value for lock acquisition.
- * However, since this thread can immediately acquire the lock
- * and does not proceed to spin on its own node->locked, this
- * value won't be used. If a debug mode is needed to
- * audit lock status, then set node->locked value here.
- */
- return;
- }
- ACCESS_ONCE(prev->next) = node;
-
- /* Wait until the lock holder passes the lock down. */
- arch_mcs_spin_lock_contended(&node->locked);
-}
-
-/*
- * Releases the lock. The caller should pass in the corresponding node that
- * was used to acquire the lock.
- */
-static inline
-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. */
- arch_mcs_spin_unlock_contended(&next->locked);
-}
-
-#endif /* __LINUX_MCS_SPINLOCK_H */
--- /dev/null
+/*
+ * MCS lock defines
+ *
+ * This file contains the main data structure and API definitions of 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
+ * to acquire the lock spinning on a local variable.
+ * It avoids expensive cache bouncings that common test-and-set spin-lock
+ * implementations incur.
+ */
+#ifndef __LINUX_MCS_SPINLOCK_H
+#define __LINUX_MCS_SPINLOCK_H
+
+#include <asm/mcs_spinlock.h>
+
+struct mcs_spinlock {
+ struct mcs_spinlock *next;
+ int locked; /* 1 if lock acquired */
+};
+
+#ifndef arch_mcs_spin_lock_contended
+/*
+ * Using smp_load_acquire() provides a memory barrier that ensures
+ * subsequent operations happen after the lock is acquired.
+ */
+#define arch_mcs_spin_lock_contended(l) \
+do { \
+ while (!(smp_load_acquire(l))) \
+ arch_mutex_cpu_relax(); \
+} while (0)
+#endif
+
+#ifndef arch_mcs_spin_unlock_contended
+/*
+ * smp_store_release() provides a memory barrier to ensure all
+ * operations in the critical section has been completed before
+ * unlocking.
+ */
+#define arch_mcs_spin_unlock_contended(l) \
+ smp_store_release((l), 1)
+#endif
+
+/*
+ * Note: the smp_load_acquire/smp_store_release pair is not
+ * sufficient to form a full memory barrier across
+ * cpus for many architectures (except x86) for mcs_unlock and mcs_lock.
+ * For applications that need a full barrier across multiple cpus
+ * with mcs_unlock and mcs_lock pair, smp_mb__after_unlock_lock() should be
+ * used after mcs_lock.
+ */
+
+/*
+ * 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 inline
+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, don't need to set node->locked to 1. Threads
+ * only spin on its own node->locked value for lock acquisition.
+ * However, since this thread can immediately acquire the lock
+ * and does not proceed to spin on its own node->locked, this
+ * value won't be used. If a debug mode is needed to
+ * audit lock status, then set node->locked value here.
+ */
+ return;
+ }
+ ACCESS_ONCE(prev->next) = node;
+
+ /* Wait until the lock holder passes the lock down. */
+ arch_mcs_spin_lock_contended(&node->locked);
+}
+
+/*
+ * Releases the lock. The caller should pass in the corresponding node that
+ * was used to acquire the lock.
+ */
+static inline
+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. */
+ arch_mcs_spin_unlock_contended(&next->locked);
+}
+
+#endif /* __LINUX_MCS_SPINLOCK_H */
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/debug_locks.h>
-#include <linux/mcs_spinlock.h>
+#include "mcs_spinlock.h"
/*
* In the DEBUG case we are using the "NULL fastpath" for mutexes,
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