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
  69 extern struct debug_obj_descr rcuhead_debug_descr;
  70
  71 static 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
  82 static 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 */
  90 static inline int debug_rcu_head_queue(struct rcu_head *head)
  91 {
  92         return 0;
  93 }
  94
  95 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
  96 {
  97 }
  98 #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
  99
 100 void kfree(const void *);
 101
 102 /*
 103  * Reclaim the specified callback, either by invoking it (non-lazy case)
 104  * or freeing it directly (lazy case).  Return true if lazy, false otherwise.
 105  */
 106 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 107 {
 108         unsigned long offset = (unsigned long)head->func;
 109
 110         rcu_lock_acquire(&rcu_callback_map);
 111         if (__is_kfree_rcu_offset(offset)) {
 112                 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
 113                 kfree((void *)head - offset);
 114                 rcu_lock_release(&rcu_callback_map);
 115                 return true;
 116         } else {
 117                 RCU_TRACE(trace_rcu_invoke_callback(rn, head));
 118                 head->func(head);
 119                 rcu_lock_release(&rcu_callback_map);
 120                 return false;
 121         }
 122 }
 123
 124 #ifdef CONFIG_RCU_STALL_COMMON
 125
 126 extern int rcu_cpu_stall_suppress;
 127 int rcu_jiffies_till_stall_check(void);
 128
 129 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 130
 131 /*
 132  * Strings used in tracepoints need to be exported via the
 133  * tracing system such that tools like perf and trace-cmd can
 134  * translate the string address pointers to actual text.
 135  */
 136 #define TPS(x)  tracepoint_string(x)
 137
 138 void rcu_early_boot_tests(void);
 139
 140 /*
 141  * This function really isn't for public consumption, but RCU is special in
 142  * that context switches can allow the state machine to make progress.
 143  */
 144 extern void resched_cpu(int cpu);
 145
 146 #endif /* __LINUX_RCU_H */