linux/kernel/rcu.h
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   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
  68extern struct debug_obj_descr rcuhead_debug_descr;
  69
  70static 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
  81static 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 */
  89static inline int debug_rcu_head_queue(struct rcu_head *head)
  90{
  91        return 0;
  92}
  93
  94static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  95{
  96}
  97#endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  98
  99extern void kfree(const void *);
 100
 101static 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
 116extern int rcu_expedited;
 117
 118#ifdef CONFIG_RCU_STALL_COMMON
 119
 120extern int rcu_cpu_stall_suppress;
 121int rcu_jiffies_till_stall_check(void);
 122
 123#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 124
 125#endif /* __LINUX_RCU_H */
 126
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