1 /* 2 * Specialised local-global spinlock. Can only be declared as global variables 3 * to avoid overhead and keep things simple (and we don't want to start using 4 * these inside dynamically allocated structures). 5 * 6 * "local/global locks" (lglocks) can be used to: 7 * 8 * - Provide fast exclusive access to per-CPU data, with exclusive access to 9 * another CPU's data allowed but possibly subject to contention, and to 10 * provide very slow exclusive access to all per-CPU data. 11 * - Or to provide very fast and scalable read serialisation, and to provide 12 * very slow exclusive serialisation of data (not necessarily per-CPU data). 13 * 14 * Brlocks are also implemented as a short-hand notation for the latter use 15 * case. 16 * 17 * Copyright 2009, 2010, Nick Piggin, Novell Inc. 18 */ 19 #ifndef __LINUX_LGLOCK_H 20 #define __LINUX_LGLOCK_H 21 22 #include <linux/spinlock.h> 23 #include <linux/lockdep.h> 24 #include <linux/percpu.h> 25 #include <linux/cpu.h> 26 #include <linux/notifier.h> 27 28 #ifdef CONFIG_SMP 29 30 #ifdef CONFIG_DEBUG_LOCK_ALLOC 31 #define LOCKDEP_INIT_MAP lockdep_init_map 32 #else 33 #define LOCKDEP_INIT_MAP(a, b, c, d) 34 #endif 35 36 struct lglock { 37 arch_spinlock_t __percpu *lock; 38 #ifdef CONFIG_DEBUG_LOCK_ALLOC 39 struct lock_class_key lock_key; 40 struct lockdep_map lock_dep_map; 41 #endif 42 }; 43 44 #define DEFINE_LGLOCK(name) \ 45 static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \ 46 = __ARCH_SPIN_LOCK_UNLOCKED; \ 47 struct lglock name = { .lock = &name ## _lock } 48 49 #define DEFINE_STATIC_LGLOCK(name) \ 50 static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \ 51 = __ARCH_SPIN_LOCK_UNLOCKED; \ 52 static struct lglock name = { .lock = &name ## _lock } 53 54 void lg_lock_init(struct lglock *lg, char *name); 55 56 void lg_local_lock(struct lglock *lg); 57 void lg_local_unlock(struct lglock *lg); 58 void lg_local_lock_cpu(struct lglock *lg, int cpu); 59 void lg_local_unlock_cpu(struct lglock *lg, int cpu); 60 61 void lg_double_lock(struct lglock *lg, int cpu1, int cpu2); 62 void lg_double_unlock(struct lglock *lg, int cpu1, int cpu2); 63 64 void lg_global_lock(struct lglock *lg); 65 void lg_global_unlock(struct lglock *lg); 66 67 #else 68 /* When !CONFIG_SMP, map lglock to spinlock */ 69 #define lglock spinlock 70 #define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name) 71 #define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name) 72 #define lg_lock_init(lg, name) spin_lock_init(lg) 73 #define lg_local_lock spin_lock 74 #define lg_local_unlock spin_unlock 75 #define lg_local_lock_cpu(lg, cpu) spin_lock(lg) 76 #define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg) 77 #define lg_global_lock spin_lock 78 #define lg_global_unlock spin_unlock 79 #endif 80 81 #endif 82