libmarkers/rcupdate.h

   1 /*
   2  * Read-Copy Update mechanism for mutual exclusion
   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, 2001
  19  *
  20  * Author: Dipankar Sarma <dipankar@in.ibm.com>
  21  *
  22  * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
  23  * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  24  * Papers:
  25  * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
  26  * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
  27  *
  28  * For detailed explanation of Read-Copy Update mechanism see -
  29  *              http://lse.sourceforge.net/locking/rcupdate.html
  30  *
  31  */
  32
  33 #ifndef __LINUX_RCUPDATE_H
  34 #define __LINUX_RCUPDATE_H
  35
  36 //ust// #include <linux/cache.h>
  37 //ust// #include <linux/spinlock.h>
  38 //ust// #include <linux/threads.h>
  39 //ust// #include <linux/percpu.h>
  40 //ust// #include <linux/cpumask.h>
  41 //ust// #include <linux/seqlock.h>
  42 //ust// #include <linux/lockdep.h>
  43 //ust// #include <linux/completion.h>
  44
  45 /**
  46  * struct rcu_head - callback structure for use with RCU
  47  * @next: next update requests in a list
  48  * @func: actual update function to call after the grace period.
  49  */
  50 struct rcu_head {
  51         struct rcu_head *next;
  52         void (*func)(struct rcu_head *head);
  53 };
  54
  55 //ust// #if defined(CONFIG_CLASSIC_RCU)
  56 //ust// #include <linux/rcuclassic.h>
  57 //ust// #elif defined(CONFIG_TREE_RCU)
  58 //ust// #include <linux/rcutree.h>
  59 //ust// #elif defined(CONFIG_PREEMPT_RCU)
  60 //ust// #include <linux/rcupreempt.h>
  61 //ust// #else
  62 //ust// #error "Unknown RCU implementation specified to kernel configuration"
  63 //ust// #endif /* #else #if defined(CONFIG_CLASSIC_RCU) */
  64 //ust//
  65 //ust// #define RCU_HEAD_INIT   { .next = NULL, .func = NULL }
  66 //ust// #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
  67 //ust// #define INIT_RCU_HEAD(ptr) do { \
  68 //ust//        (ptr)->next = NULL; (ptr)->func = NULL; \
  69 //ust// } while (0)
  70 //ust//
  71 //ust// /**
  72 //ust//  * rcu_read_lock - mark the beginning of an RCU read-side critical section.
  73 //ust//  *
  74 //ust//  * When synchronize_rcu() is invoked on one CPU while other CPUs
  75 //ust//  * are within RCU read-side critical sections, then the
  76 //ust//  * synchronize_rcu() is guaranteed to block until after all the other
  77 //ust//  * CPUs exit their critical sections.  Similarly, if call_rcu() is invoked
  78 //ust//  * on one CPU while other CPUs are within RCU read-side critical
  79 //ust//  * sections, invocation of the corresponding RCU callback is deferred
  80 //ust//  * until after the all the other CPUs exit their critical sections.
  81 //ust//  *
  82 //ust//  * Note, however, that RCU callbacks are permitted to run concurrently
  83 //ust//  * with RCU read-side critical sections.  One way that this can happen
  84 //ust//  * is via the following sequence of events: (1) CPU 0 enters an RCU
  85 //ust//  * read-side critical section, (2) CPU 1 invokes call_rcu() to register
  86 //ust//  * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
  87 //ust//  * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
  88 //ust//  * callback is invoked.  This is legal, because the RCU read-side critical
  89 //ust//  * section that was running concurrently with the call_rcu() (and which
  90 //ust//  * therefore might be referencing something that the corresponding RCU
  91 //ust//  * callback would free up) has completed before the corresponding
  92 //ust//  * RCU callback is invoked.
  93 //ust//  *
  94 //ust//  * RCU read-side critical sections may be nested.  Any deferred actions
  95 //ust//  * will be deferred until the outermost RCU read-side critical section
  96 //ust//  * completes.
  97 //ust//  *
  98 //ust//  * It is illegal to block while in an RCU read-side critical section.
  99 //ust//  */
 100 //ust// #define rcu_read_lock() __rcu_read_lock()
 101 //ust//
 102 //ust// /**
 103 //ust//  * rcu_read_unlock - marks the end of an RCU read-side critical section.
 104 //ust//  *
 105 //ust//  * See rcu_read_lock() for more information.
 106 //ust//  */
 107 //ust//
 108 //ust// /*
 109 //ust//  * So where is rcu_write_lock()?  It does not exist, as there is no
 110 //ust//  * way for writers to lock out RCU readers.  This is a feature, not
 111 //ust//  * a bug -- this property is what provides RCU's performance benefits.
 112 //ust//  * Of course, writers must coordinate with each other.  The normal
 113 //ust//  * spinlock primitives work well for this, but any other technique may be
 114 //ust//  * used as well.  RCU does not care how the writers keep out of each
 115 //ust//  * others' way, as long as they do so.
 116 //ust//  */
 117 //ust// #define rcu_read_unlock() __rcu_read_unlock()
 118 //ust//
 119 //ust// /**
 120 //ust//  * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section
 121 //ust//  *
 122 //ust//  * This is equivalent of rcu_read_lock(), but to be used when updates
 123 //ust//  * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks
 124 //ust//  * consider completion of a softirq handler to be a quiescent state,
 125 //ust//  * a process in RCU read-side critical section must be protected by
 126 //ust//  * disabling softirqs. Read-side critical sections in interrupt context
 127 //ust//  * can use just rcu_read_lock().
 128 //ust//  *
 129 //ust//  */
 130 //ust// #define rcu_read_lock_bh() __rcu_read_lock_bh()
 131 //ust//
 132 //ust// /*
 133 //ust//  * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
 134 //ust//  *
 135 //ust//  * See rcu_read_lock_bh() for more information.
 136 //ust//  */
 137 //ust// #define rcu_read_unlock_bh() __rcu_read_unlock_bh()
 138 //ust//
 139 //ust// /**
 140 //ust//  * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section
 141 //ust//  *
 142 //ust//  * Should be used with either
 143 //ust//  * - synchronize_sched()
 144 //ust//  * or
 145 //ust//  * - call_rcu_sched() and rcu_barrier_sched()
 146 //ust//  * on the write-side to insure proper synchronization.
 147 //ust//  */
 148 //ust// #define rcu_read_lock_sched() preempt_disable()
 149 //ust// #define rcu_read_lock_sched_notrace() preempt_disable_notrace()
 150 //ust//
 151 //ust// /*
 152 //ust//  * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
 153 //ust//  *
 154 //ust//  * See rcu_read_lock_sched for more information.
 155 //ust//  */
 156 //ust// #define rcu_read_unlock_sched() preempt_enable()
 157 //ust// #define rcu_read_unlock_sched_notrace() preempt_enable_notrace()
 158 //ust//
 159 //ust//
 160 //ust//
 161 //ust// /**
 162 //ust//  * rcu_dereference - fetch an RCU-protected pointer in an
 163 //ust//  * RCU read-side critical section.  This pointer may later
 164 //ust//  * be safely dereferenced.
 165 //ust//  *
 166 //ust//  * Inserts memory barriers on architectures that require them
 167 //ust//  * (currently only the Alpha), and, more importantly, documents
 168 //ust//  * exactly which pointers are protected by RCU.
 169 //ust//  */
 170 //ust//
 171 //ust// #define rcu_dereference(p)     ({ \
 172 //ust//                                 typeof(p) _________p1 = ACCESS_ONCE(p); \
 173 //ust//                                 smp_read_barrier_depends(); \
 174 //ust//                                 (_________p1); \
 175 //ust//                                 })
 176 //ust//
 177 //ust// /**
 178 //ust//  * rcu_assign_pointer - assign (publicize) a pointer to a newly
 179 //ust//  * initialized structure that will be dereferenced by RCU read-side
 180 //ust//  * critical sections.  Returns the value assigned.
 181 //ust//  *
 182 //ust//  * Inserts memory barriers on architectures that require them
 183 //ust//  * (pretty much all of them other than x86), and also prevents
 184 //ust//  * the compiler from reordering the code that initializes the
 185 //ust//  * structure after the pointer assignment.  More importantly, this
 186 //ust//  * call documents which pointers will be dereferenced by RCU read-side
 187 //ust//  * code.
 188 //ust//  */
 189 //ust//
 190 //ust// #define rcu_assign_pointer(p, v) \
 191 //ust//         ({ \
 192 //ust//                 if (!__builtin_constant_p(v) || \
 193 //ust//                     ((v) != NULL)) \
 194 //ust//                         smp_wmb(); \
 195 //ust//                 (p) = (v); \
 196 //ust//         })
 197 //ust//
 198 //ust// /* Infrastructure to implement the synchronize_() primitives. */
 199 //ust//
 200 //ust// struct rcu_synchronize {
 201 //ust//         struct rcu_head head;
 202 //ust//         struct completion completion;
 203 //ust// };
 204 //ust//
 205 //ust// extern void wakeme_after_rcu(struct rcu_head  *head);
 206 //ust//
 207 //ust// /**
 208 //ust//  * synchronize_sched - block until all CPUs have exited any non-preemptive
 209 //ust//  * kernel code sequences.
 210 //ust//  *
 211 //ust//  * This means that all preempt_disable code sequences, including NMI and
 212 //ust//  * hardware-interrupt handlers, in progress on entry will have completed
 213 //ust//  * before this primitive returns.  However, this does not guarantee that
 214 //ust//  * softirq handlers will have completed, since in some kernels, these
 215 //ust//  * handlers can run in process context, and can block.
 216 //ust//  *
 217 //ust//  * This primitive provides the guarantees made by the (now removed)
 218 //ust//  * synchronize_kernel() API.  In contrast, synchronize_rcu() only
 219 //ust//  * guarantees that rcu_read_lock() sections will have completed.
 220 //ust//  * In "classic RCU", these two guarantees happen to be one and
 221 //ust//  * the same, but can differ in realtime RCU implementations.
 222 //ust//  */
 223 //ust// #define synchronize_sched() __synchronize_sched()
 224 //ust//
 225 //ust// /**
 226 //ust//  * call_rcu - Queue an RCU callback for invocation after a grace period.
 227 //ust//  * @head: structure to be used for queueing the RCU updates.
 228 //ust//  * @func: actual update function to be invoked after the grace period
 229 //ust//  *
 230 //ust//  * The update function will be invoked some time after a full grace
 231 //ust//  * period elapses, in other words after all currently executing RCU
 232 //ust//  * read-side critical sections have completed.  RCU read-side critical
 233 //ust//  * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
 234 //ust//  * and may be nested.
 235 //ust//  */
 236 //ust// extern void call_rcu(struct rcu_head *head,
 237 //ust//                               void (*func)(struct rcu_head *head));
 238 //ust//
 239 //ust// /**
 240 //ust//  * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
 241 //ust//  * @head: structure to be used for queueing the RCU updates.
 242 //ust//  * @func: actual update function to be invoked after the grace period
 243 //ust//  *
 244 //ust//  * The update function will be invoked some time after a full grace
 245 //ust//  * period elapses, in other words after all currently executing RCU
 246 //ust//  * read-side critical sections have completed. call_rcu_bh() assumes
 247 //ust//  * that the read-side critical sections end on completion of a softirq
 248 //ust//  * handler. This means that read-side critical sections in process
 249 //ust//  * context must not be interrupted by softirqs. This interface is to be
 250 //ust//  * used when most of the read-side critical sections are in softirq context.
 251 //ust//  * RCU read-side critical sections are delimited by :
 252 //ust//  *  - rcu_read_lock() and  rcu_read_unlock(), if in interrupt context.
 253 //ust//  *  OR
 254 //ust//  *  - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.
 255 //ust//  *  These may be nested.
 256 //ust//  */
 257 //ust// extern void call_rcu_bh(struct rcu_head *head,
 258 //ust//                         void (*func)(struct rcu_head *head));
 259 //ust//
 260 //ust// /* Exported common interfaces */
 261 //ust// extern void synchronize_rcu(void);
 262 //ust// extern void rcu_barrier(void);
 263 //ust// extern void rcu_barrier_bh(void);
 264 //ust// extern void rcu_barrier_sched(void);
 265 //ust//
 266 //ust// /* Internal to kernel */
 267 //ust// extern void rcu_init(void);
 268 //ust// extern int rcu_needs_cpu(int cpu);
 269 //ust//
 270 #endif /* __LINUX_RCUPDATE_H */