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  * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
  38  * that counts the number of process-based reasons why RCU cannot
  39  * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
  40  * is the value used to increment or decrement this field.
  41  *
  42  * The rest of the bits could in principle be used to count interrupts,
  43  * but this would mean that a negative-one value in the interrupt
  44  * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
  45  * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
  46  * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
  47  * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
  48  * initial exit from idle.
  49  */
  50 #define DYNTICK_TASK_NEST_WIDTH 7
  51 #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
  52 #define DYNTICK_TASK_NEST_MASK  (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
  53 #define DYNTICK_TASK_FLAG          ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
  54 #define DYNTICK_TASK_MASK          ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
  55 #define DYNTICK_TASK_EXIT_IDLE     (DYNTICK_TASK_NEST_VALUE + \
  56                                     DYNTICK_TASK_FLAG)
  57
  58 /*
  59  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
  60  * by call_rcu() and rcu callback execution, and are therefore not part of the
  61  * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
  62  */
  63
  64 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
  65 # define STATE_RCU_HEAD_READY   0
  66 # define STATE_RCU_HEAD_QUEUED  1
  67
  68 extern struct debug_obj_descr rcuhead_debug_descr;
  69
  70 static inline int debug_rcu_head_queue(struct rcu_head *head)
  71 {
  72         int r1;
  73
  74         r1 = debug_object_activate(head, &rcuhead_debug_descr);
  75         debug_object_active_state(head, &rcuhead_debug_descr,
  76                                   STATE_RCU_HEAD_READY,
  77                                   STATE_RCU_HEAD_QUEUED);
  78         return r1;
  79 }
  80
  81 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  82 {
  83         debug_object_active_state(head, &rcuhead_debug_descr,
  84                                   STATE_RCU_HEAD_QUEUED,
  85                                   STATE_RCU_HEAD_READY);
  86         debug_object_deactivate(head, &rcuhead_debug_descr);
  87 }
  88 #else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  89 static inline int debug_rcu_head_queue(struct rcu_head *head)
  90 {
  91         return 0;
  92 }
  93
  94 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  95 {
  96 }
  97 #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  98
  99 extern void kfree(const void *);
 100
 101 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 102 {
 103         unsigned long offset = (unsigned long)head->func;
 104
 105         if (__is_kfree_rcu_offset(offset)) {
 106                 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
 107                 kfree((void *)head - offset);
 108                 return 1;
 109         } else {
 110                 RCU_TRACE(trace_rcu_invoke_callback(rn, head));
 111                 head->func(head);
 112                 return 0;
 113         }
 114 }
 115
 116 extern int rcu_expedited;
 117
 118 #ifdef CONFIG_RCU_STALL_COMMON
 119
 120 extern int rcu_cpu_stall_suppress;
 121 int rcu_jiffies_till_stall_check(void);
 122
 123 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 124
 125 #endif /* __LINUX_RCU_H */