include/linux/lglock.h

   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 void lg_local_lock(struct lglock *lg);
  56 void lg_local_unlock(struct lglock *lg);
  57 void lg_local_lock_cpu(struct lglock *lg, int cpu);
  58 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  59 void lg_global_lock(struct lglock *lg);
  60 void lg_global_unlock(struct lglock *lg);
  61
  62 #else
  63 /* When !CONFIG_SMP, map lglock to spinlock */
  64 #define lglock spinlock
  65 #define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
  66 #define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
  67 #define lg_lock_init(lg, name) spin_lock_init(lg)
  68 #define lg_local_lock spin_lock
  69 #define lg_local_unlock spin_unlock
  70 #define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
  71 #define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
  72 #define lg_global_lock spin_lock
  73 #define lg_global_unlock spin_unlock
  74 #endif
  75
  76 #endif