include/linux/rcu_sync.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * RCU-based infrastructure for lightweight reader-writer locking
   4  *
   5  * Copyright (c) 2015, Red Hat, Inc.
   6  *
   7  * Author: Oleg Nesterov <oleg@redhat.com>
   8  */
   9
  10 #ifndef _LINUX_RCU_SYNC_H_
  11 #define _LINUX_RCU_SYNC_H_
  12
  13 #include <linux/wait.h>
  14 #include <linux/rcupdate.h>
  15
  16 enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
  17
  18 /* Structure to mediate between updaters and fastpath-using readers.  */
  19 struct rcu_sync {
  20         int                     gp_state;
  21         int                     gp_count;
  22         wait_queue_head_t       gp_wait;
  23
  24         int                     cb_state;
  25         struct rcu_head         cb_head;
  26
  27         enum rcu_sync_type      gp_type;
  28 };
  29
  30 extern void rcu_sync_lockdep_assert(struct rcu_sync *);
  31
  32 /**
  33  * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
  34  * @rsp: Pointer to rcu_sync structure to use for synchronization
  35  *
  36  * Returns true if readers are permitted to use their fastpaths.
  37  * Must be invoked within an RCU read-side critical section whose
  38  * flavor matches that of the rcu_sync struture.
  39  */
  40 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
  41 {
  42 #ifdef CONFIG_PROVE_RCU
  43         rcu_sync_lockdep_assert(rsp);
  44 #endif
  45         return !rsp->gp_state; /* GP_IDLE */
  46 }
  47
  48 extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
  49 extern void rcu_sync_enter_start(struct rcu_sync *);
  50 extern void rcu_sync_enter(struct rcu_sync *);
  51 extern void rcu_sync_exit(struct rcu_sync *);
  52 extern void rcu_sync_dtor(struct rcu_sync *);
  53
  54 #define __RCU_SYNC_INITIALIZER(name, type) {                            \
  55                 .gp_state = 0,                                          \
  56                 .gp_count = 0,                                          \
  57                 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
  58                 .cb_state = 0,                                          \
  59                 .gp_type = type,                                        \
  60         }
  61
  62 #define __DEFINE_RCU_SYNC(name, type)   \
  63         struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
  64
  65 #define DEFINE_RCU_SYNC(name)           \
  66         __DEFINE_RCU_SYNC(name, RCU_SYNC)
  67
  68 #define DEFINE_RCU_SCHED_SYNC(name)     \
  69         __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
  70
  71 #define DEFINE_RCU_BH_SYNC(name)        \
  72         __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
  73
  74 #endif /* _LINUX_RCU_SYNC_H_ */