include/linux/rcu_sync.h

   1 /*
   2  * RCU-based infrastructure for lightweight reader-writer locking
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, you can access it online at
  16  * http://www.gnu.org/licenses/gpl-2.0.html.
  17  *
  18  * Copyright (c) 2015, Red Hat, Inc.
  19  *
  20  * Author: Oleg Nesterov <oleg@redhat.com>
  21  */
  22
  23 #ifndef _LINUX_RCU_SYNC_H_
  24 #define _LINUX_RCU_SYNC_H_
  25
  26 #include <linux/wait.h>
  27 #include <linux/rcupdate.h>
  28
  29 enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
  30
  31 /* Structure to mediate between updaters and fastpath-using readers.  */
  32 struct rcu_sync {
  33         int                     gp_state;
  34         int                     gp_count;
  35         wait_queue_head_t       gp_wait;
  36
  37         int                     cb_state;
  38         struct rcu_head         cb_head;
  39
  40         enum rcu_sync_type      gp_type;
  41 };
  42
  43 extern void rcu_sync_lockdep_assert(struct rcu_sync *);
  44
  45 /**
  46  * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
  47  * @rsp: Pointer to rcu_sync structure to use for synchronization
  48  *
  49  * Returns true if readers are permitted to use their fastpaths.
  50  * Must be invoked within an RCU read-side critical section whose
  51  * flavor matches that of the rcu_sync struture.
  52  */
  53 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
  54 {
  55 #ifdef CONFIG_PROVE_RCU
  56         rcu_sync_lockdep_assert(rsp);
  57 #endif
  58         return !rsp->gp_state; /* GP_IDLE */
  59 }
  60
  61 extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
  62 extern void rcu_sync_enter_start(struct rcu_sync *);
  63 extern void rcu_sync_enter(struct rcu_sync *);
  64 extern void rcu_sync_exit(struct rcu_sync *);
  65 extern void rcu_sync_dtor(struct rcu_sync *);
  66
  67 #define __RCU_SYNC_INITIALIZER(name, type) {                            \
  68                 .gp_state = 0,                                          \
  69                 .gp_count = 0,                                          \
  70                 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
  71                 .cb_state = 0,                                          \
  72                 .gp_type = type,                                        \
  73         }
  74
  75 #define __DEFINE_RCU_SYNC(name, type)   \
  76         struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
  77
  78 #define DEFINE_RCU_SYNC(name)           \
  79         __DEFINE_RCU_SYNC(name, RCU_SYNC)
  80
  81 #define DEFINE_RCU_SCHED_SYNC(name)     \
  82         __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
  83
  84 #define DEFINE_RCU_BH_SYNC(name)        \
  85         __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
  86
  87 #endif /* _LINUX_RCU_SYNC_H_ */