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 /* can make br locks by using local lock for read side, global lock for write */
  29 #define br_lock_init(name)      lg_lock_init(name, #name)
  30 #define br_read_lock(name)      lg_local_lock(name)
  31 #define br_read_unlock(name)    lg_local_unlock(name)
  32 #define br_write_lock(name)     lg_global_lock(name)
  33 #define br_write_unlock(name)   lg_global_unlock(name)
  34
  35 #define DEFINE_BRLOCK(name)     DEFINE_LGLOCK(name)
  36
  37 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  38 #define LOCKDEP_INIT_MAP lockdep_init_map
  39
  40 #define DEFINE_LGLOCK_LOCKDEP(name)                                     \
  41  struct lock_class_key name##_lock_key;                                 \
  42  struct lockdep_map name##_lock_dep_map;                                \
  43  EXPORT_SYMBOL(name##_lock_dep_map)
  44
  45 #else
  46 #define LOCKDEP_INIT_MAP(a, b, c, d)
  47
  48 #define DEFINE_LGLOCK_LOCKDEP(name)
  49 #endif
  50
  51 struct lglock {
  52         arch_spinlock_t __percpu *lock;
  53 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  54         struct lock_class_key lock_key;
  55         struct lockdep_map    lock_dep_map;
  56 #endif
  57 };
  58
  59 #define DEFINE_LGLOCK(name)                                             \
  60         DEFINE_LGLOCK_LOCKDEP(name);                                    \
  61         DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)                  \
  62         = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  63         struct lglock name = { .lock = &name ## _lock }
  64
  65 void lg_lock_init(struct lglock *lg, char *name);
  66 void lg_local_lock(struct lglock *lg);
  67 void lg_local_unlock(struct lglock *lg);
  68 void lg_local_lock_cpu(struct lglock *lg, int cpu);
  69 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  70 void lg_global_lock(struct lglock *lg);
  71 void lg_global_unlock(struct lglock *lg);
  72
  73 #endif