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 /* Structure to mediate between updaters and fastpath-using readers.  */
  17 struct rcu_sync {
  18         int                     gp_state;
  19         int                     gp_count;
  20         wait_queue_head_t       gp_wait;
  21
  22         struct rcu_head         cb_head;
  23 };
  24
  25 /**
  26  * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
  27  * @rsp: Pointer to rcu_sync structure to use for synchronization
  28  *
  29  * Returns true if readers are permitted to use their fastpaths.  Must be
  30  * invoked within some flavor of RCU read-side critical section.
  31  */
  32 static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
  33 {
  34         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
  35                          !rcu_read_lock_bh_held() &&
  36                          !rcu_read_lock_sched_held(),
  37                          "suspicious rcu_sync_is_idle() usage");
  38         return !READ_ONCE(rsp->gp_state); /* GP_IDLE */
  39 }
  40
  41 extern void rcu_sync_init(struct rcu_sync *);
  42 extern void rcu_sync_enter_start(struct rcu_sync *);
  43 extern void rcu_sync_enter(struct rcu_sync *);
  44 extern void rcu_sync_exit(struct rcu_sync *);
  45 extern void rcu_sync_dtor(struct rcu_sync *);
  46
  47 #define __RCU_SYNC_INITIALIZER(name) {                                  \
  48                 .gp_state = 0,                                          \
  49                 .gp_count = 0,                                          \
  50                 .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
  51         }
  52
  53 #define DEFINE_RCU_SYNC(name)   \
  54         struct rcu_sync name = __RCU_SYNC_INITIALIZER(name)
  55
  56 #endif /* _LINUX_RCU_SYNC_H_ */