diff options
| -rw-r--r-- | include/linux/mcs_spinlock.h | 42 |
1 files changed, 28 insertions, 14 deletions
diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h index 143fa428a857..e9a4d74c63dc 100644 --- a/include/linux/mcs_spinlock.h +++ b/include/linux/mcs_spinlock.h @@ -17,6 +17,28 @@ struct mcs_spinlock { 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 @@ -58,13 +80,9 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node) 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(); + + /* Wait until the lock holder passes the lock down. */ + arch_mcs_spin_lock_contended(&node->locked); } /* @@ -86,13 +104,9 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) 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); + + /* Pass lock to next waiter. */ + arch_mcs_spin_unlock_contended(&next->locked); } #endif /* __LINUX_MCS_SPINLOCK_H */ |