LXR linux/kernel/rcu/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, you can access it online at
  16 * http://www.gnu.org/licenses/gpl-2.0.html.
  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#include <trace/events/rcu.h>
  27#ifdef CONFIG_RCU_TRACE
  28#define RCU_TRACE(stmt) stmt
  29#else /* #ifdef CONFIG_RCU_TRACE */
  30#define RCU_TRACE(stmt)
  31#endif /* #else #ifdef CONFIG_RCU_TRACE */
  32
  33/*
  34 * Process-level increment to ->dynticks_nesting field.  This allows for
  35 * architectures that use half-interrupts and half-exceptions from
  36 * process context.
  37 *
  38 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
  39 * that counts the number of process-based reasons why RCU cannot
  40 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
  41 * is the value used to increment or decrement this field.
  42 *
  43 * The rest of the bits could in principle be used to count interrupts,
  44 * but this would mean that a negative-one value in the interrupt
  45 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
  46 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
  47 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
  48 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
  49 * initial exit from idle.
  50 */
  51#define DYNTICK_TASK_NEST_WIDTH 7
  52#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
  53#define DYNTICK_TASK_NEST_MASK  (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
  54#define DYNTICK_TASK_FLAG          ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
  55#define DYNTICK_TASK_MASK          ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
  56#define DYNTICK_TASK_EXIT_IDLE     (DYNTICK_TASK_NEST_VALUE + \
  57                                    DYNTICK_TASK_FLAG)
  58
  59/*
  60 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
  61 * by call_rcu() and rcu callback execution, and are therefore not part of the
  62 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
  63 */
  64
  65#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
  66# define STATE_RCU_HEAD_READY   0
  67# define STATE_RCU_HEAD_QUEUED  1
  68
  69extern struct debug_obj_descr rcuhead_debug_descr;
  70
  71static inline int debug_rcu_head_queue(struct rcu_head *head)
  72{
  73        int r1;
  74
  75        r1 = debug_object_activate(head, &rcuhead_debug_descr);
  76        debug_object_active_state(head, &rcuhead_debug_descr,
  77                                  STATE_RCU_HEAD_READY,
  78                                  STATE_RCU_HEAD_QUEUED);
  79        return r1;
  80}
  81
  82static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  83{
  84        debug_object_active_state(head, &rcuhead_debug_descr,
  85                                  STATE_RCU_HEAD_QUEUED,
  86                                  STATE_RCU_HEAD_READY);
  87        debug_object_deactivate(head, &rcuhead_debug_descr);
  88}
  89#else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  90static inline int debug_rcu_head_queue(struct rcu_head *head)
  91{
  92        return 0;
  93}
  94
  95static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  96{
  97}
  98#endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  99
 100void kfree(const void *);
 101
 102static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 103{
 104        unsigned long offset = (unsigned long)head->func;
 105
 106        rcu_lock_acquire(&rcu_callback_map);
 107        if (__is_kfree_rcu_offset(offset)) {
 108                RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
 109                kfree((void *)head - offset);
 110                rcu_lock_release(&rcu_callback_map);
 111                return 1;
 112        } else {
 113                RCU_TRACE(trace_rcu_invoke_callback(rn, head));
 114                head->func(head);
 115                rcu_lock_release(&rcu_callback_map);
 116                return 0;
 117        }
 118}
 119
 120#ifdef CONFIG_RCU_STALL_COMMON
 121
 122extern int rcu_cpu_stall_suppress;
 123int rcu_jiffies_till_stall_check(void);
 124
 125#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 126
 127/*
 128 * Strings used in tracepoints need to be exported via the
 129 * tracing system such that tools like perf and trace-cmd can
 130 * translate the string address pointers to actual text.
 131 */
 132#define TPS(x)  tracepoint_string(x)
 133
 134#endif /* __LINUX_RCU_H */
 135