kernel/rcu.h

   1 /*
   2  * Read-Copy Update definitions shared among RCU implementations.
   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, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright IBM Corporation, 2011
  19  *
  20  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  21  */
  22
  23 #ifndef __LINUX_RCU_H
  24 #define __LINUX_RCU_H
  25
  26 #ifdef CONFIG_RCU_TRACE
  27 #define RCU_TRACE(stmt) stmt
  28 #else /* #ifdef CONFIG_RCU_TRACE */
  29 #define RCU_TRACE(stmt)
  30 #endif /* #else #ifdef CONFIG_RCU_TRACE */
  31
  32 /*
  33  * Process-level increment to ->dynticks_nesting field.  This allows for
  34  * architectures that use half-interrupts and half-exceptions from
  35  * process context.
  36  */
  37 #define DYNTICK_TASK_NESTING (LLONG_MAX / 2 - 1)
  38
  39 /*
  40  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
  41  * by call_rcu() and rcu callback execution, and are therefore not part of the
  42  * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
  43  */
  44
  45 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
  46 # define STATE_RCU_HEAD_READY   0
  47 # define STATE_RCU_HEAD_QUEUED  1
  48
  49 extern struct debug_obj_descr rcuhead_debug_descr;
  50
  51 static inline void debug_rcu_head_queue(struct rcu_head *head)
  52 {
  53         debug_object_activate(head, &rcuhead_debug_descr);
  54         debug_object_active_state(head, &rcuhead_debug_descr,
  55                                   STATE_RCU_HEAD_READY,
  56                                   STATE_RCU_HEAD_QUEUED);
  57 }
  58
  59 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  60 {
  61         debug_object_active_state(head, &rcuhead_debug_descr,
  62                                   STATE_RCU_HEAD_QUEUED,
  63                                   STATE_RCU_HEAD_READY);
  64         debug_object_deactivate(head, &rcuhead_debug_descr);
  65 }
  66 #else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  67 static inline void debug_rcu_head_queue(struct rcu_head *head)
  68 {
  69 }
  70
  71 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  72 {
  73 }
  74 #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  75
  76 extern void kfree(const void *);
  77
  78 static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
  79 {
  80         unsigned long offset = (unsigned long)head->func;
  81
  82         if (__is_kfree_rcu_offset(offset)) {
  83                 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
  84                 kfree((void *)head - offset);
  85                 return 1;
  86         } else {
  87                 RCU_TRACE(trace_rcu_invoke_callback(rn, head));
  88                 head->func(head);
  89                 return 0;
  90         }
  91 }
  92
  93 #endif /* __LINUX_RCU_H */