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 #define DEFINE_STATIC_BRLOCK(name)      DEFINE_STATIC_LGLOCK(name)
  37
  38 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  39 #define LOCKDEP_INIT_MAP lockdep_init_map
  40 #else
  41 #define LOCKDEP_INIT_MAP(a, b, c, d)
  42 #endif
  43
  44 struct lglock {
  45         arch_spinlock_t __percpu *lock;
  46 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  47         struct lock_class_key lock_key;
  48         struct lockdep_map    lock_dep_map;
  49 #endif
  50 };
  51
  52 #define DEFINE_LGLOCK(name)                                             \
  53         static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  54         = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  55         struct lglock name = { .lock = &name ## _lock }
  56
  57 #define DEFINE_STATIC_LGLOCK(name)                                      \
  58         static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  59         = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  60         static struct lglock name = { .lock = &name ## _lock }
  61
  62 void lg_lock_init(struct lglock *lg, char *name);
  63 void lg_local_lock(struct lglock *lg);
  64 void lg_local_unlock(struct lglock *lg);
  65 void lg_local_lock_cpu(struct lglock *lg, int cpu);
  66 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  67 void lg_global_lock(struct lglock *lg);
  68 void lg_global_unlock(struct lglock *lg);
  69
  70 #endif