sys/sys/spinlock2.h

   1 /*
   2  * Copyright (c) 2005 Jeffrey M. Hsu.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Jeffrey M. Hsu.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of The DragonFly Project nor the names of its
  16  *    contributors may be used to endorse or promote products derived
  17  *    from this software without specific, prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  22  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  23  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  24  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  25  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  26  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  27  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #ifndef _SYS_SPINLOCK2_H_
  34 #define _SYS_SPINLOCK2_H_
  35
  36 #ifndef _KERNEL
  37 #error "This file should not be included by userland programs."
  38 #endif
  39
  40 #ifndef _SYS_SYSTM_H_
  41 #include <sys/systm.h>
  42 #endif
  43 #ifndef _SYS_THREAD2_H_
  44 #include <sys/thread2.h>
  45 #endif
  46 #ifndef _SYS_GLOBALDATA_H_
  47 #include <sys/globaldata.h>
  48 #endif
  49 #include <machine/atomic.h>
  50 #include <machine/cpufunc.h>
  51
  52 extern struct spinlock pmap_spin;
  53
  54 int spin_trylock_contested(struct spinlock *spin);
  55 void _spin_lock_contested(struct spinlock *spin, const char *ident, int count);
  56 void _spin_lock_shared_contested(struct spinlock *spin, const char *ident);
  57
  58 #define spin_lock(spin)                 _spin_lock(spin, __func__)
  59 #define spin_lock_quick(spin)           _spin_lock_quick(spin, __func__)
  60 #define spin_lock_shared(spin)          _spin_lock_shared(spin, __func__)
  61 #define spin_lock_shared_quick(spin)    _spin_lock_shared_quick(spin, __func__)
  62
  63 /*
  64  * Attempt to obtain an exclusive spinlock.  Returns FALSE on failure,
  65  * TRUE on success.
  66  */
  67 static __inline boolean_t
  68 spin_trylock(struct spinlock *spin)
  69 {
  70         globaldata_t gd = mycpu;
  71
  72         crit_enter_raw(gd->gd_curthread);
  73         ++gd->gd_spinlocks;
  74         cpu_ccfence();
  75         if (atomic_cmpset_int(&spin->lock, 0, 1) == 0)
  76                 return (spin_trylock_contested(spin));
  77 #ifdef DEBUG_LOCKS
  78         int i;
  79         for (i = 0; i < SPINLOCK_DEBUG_ARRAY_SIZE; i++) {
  80                 if (gd->gd_curthread->td_spinlock_stack_id[i] == 0) {
  81                         gd->gd_curthread->td_spinlock_stack_id[i] = 1;
  82                         gd->gd_curthread->td_spinlock_stack[i] = spin;
  83                         gd->gd_curthread->td_spinlock_caller_pc[i] =
  84                                 __builtin_return_address(0);
  85                         break;
  86                 }
  87         }
  88 #endif
  89         return (TRUE);
  90 }
  91
  92 /*
  93  * Return TRUE if the spinlock is held (we can't tell by whom, though)
  94  */
  95 static __inline int
  96 spin_held(struct spinlock *spin)
  97 {
  98         return((spin->lock & ~SPINLOCK_SHARED) != 0);
  99 }
 100
 101 /*
 102  * Obtain an exclusive spinlock and return.  It is possible for the
 103  * SPINLOCK_SHARED bit to already be set, in which case the contested
 104  * code is called to fix it up.
 105  */
 106 static __inline void
 107 _spin_lock_quick(globaldata_t gd, struct spinlock *spin, const char *ident)
 108 {
 109         int count;
 110
 111         crit_enter_raw(gd->gd_curthread);
 112         ++gd->gd_spinlocks;
 113         cpu_ccfence();
 114
 115         count = atomic_fetchadd_int(&spin->lock, 1);
 116         if (__predict_false(count != 0)) {
 117                 _spin_lock_contested(spin, ident, count);
 118         }
 119 #ifdef DEBUG_LOCKS
 120         int i;
 121         for (i = 0; i < SPINLOCK_DEBUG_ARRAY_SIZE; i++) {
 122                 if (gd->gd_curthread->td_spinlock_stack_id[i] == 0) {
 123                         gd->gd_curthread->td_spinlock_stack_id[i] = 1;
 124                         gd->gd_curthread->td_spinlock_stack[i] = spin;
 125                         gd->gd_curthread->td_spinlock_caller_pc[i] =
 126                                 __builtin_return_address(0);
 127                         break;
 128                 }
 129         }
 130 #endif
 131 }
 132
 133 static __inline void
 134 _spin_lock(struct spinlock *spin, const char *ident)
 135 {
 136         _spin_lock_quick(mycpu, spin, ident);
 137 }
 138
 139 /*
 140  * Release an exclusive spinlock.  We can just do this passively, only
 141  * ensuring that our spinlock count is left intact until the mutex is
 142  * cleared.
 143  *
 144  * NOTE: Actually works for shared OR exclusive spinlocks.  spin_unlock_any()
 145  *       assumes this too.
 146  */
 147 static __inline void
 148 spin_unlock_quick(globaldata_t gd, struct spinlock *spin)
 149 {
 150 #ifdef DEBUG_LOCKS
 151         int i;
 152         for (i = 0; i < SPINLOCK_DEBUG_ARRAY_SIZE; i++) {
 153                 if ((gd->gd_curthread->td_spinlock_stack_id[i] == 1) &&
 154                     (gd->gd_curthread->td_spinlock_stack[i] == spin)) {
 155                         gd->gd_curthread->td_spinlock_stack_id[i] = 0;
 156                         gd->gd_curthread->td_spinlock_stack[i] = NULL;
 157                         gd->gd_curthread->td_spinlock_caller_pc[i] = NULL;
 158                         break;
 159                 }
 160         }
 161 #endif
 162         /*
 163          * Don't use a locked instruction here.  To reduce latency we avoid
 164          * reading spin->lock prior to writing to it.
 165          */
 166 #ifdef DEBUG_LOCKS
 167         KKASSERT(spin->lock != 0);
 168 #endif
 169         cpu_sfence();
 170         atomic_add_int(&spin->lock, -1);
 171         cpu_sfence();
 172 #ifdef DEBUG_LOCKS
 173         KKASSERT(gd->gd_spinlocks > 0);
 174 #endif
 175         cpu_ccfence();
 176         --gd->gd_spinlocks;
 177         crit_exit_quick(gd->gd_curthread);
 178 }
 179
 180 static __inline void
 181 spin_unlock(struct spinlock *spin)
 182 {
 183         spin_unlock_quick(mycpu, spin);
 184 }
 185
 186 static __inline void
 187 spin_unlock_any(struct spinlock *spin)
 188 {
 189         spin_unlock_quick(mycpu, spin);
 190 }
 191
 192 /*
 193  * Shared spinlock.  Acquire a count, if SPINLOCK_SHARED is not already
 194  * set then try a trivial conversion and drop into the contested code if
 195  * the trivial cocnversion fails.  The SHARED bit is 'cached' when lock
 196  * counts go to 0 so the critical path is typically just the fetchadd.
 197  *
 198  * WARNING!  Due to the way exclusive conflict resolution works, we cannot
 199  *           just unconditionally set the SHARED bit on previous-count == 0.
 200  *           Doing so will interfere with the exclusive contended code.
 201  */
 202 static __inline void
 203 _spin_lock_shared_quick(globaldata_t gd, struct spinlock *spin,
 204                         const char *ident)
 205 {
 206         int lock;
 207
 208         crit_enter_raw(gd->gd_curthread);
 209         ++gd->gd_spinlocks;
 210         cpu_ccfence();
 211
 212         lock = atomic_fetchadd_int(&spin->lock, 1);
 213         if (__predict_false((lock & SPINLOCK_SHARED) == 0)) {
 214                 if (lock != 0 ||
 215                     !atomic_cmpset_int(&spin->lock, 1, SPINLOCK_SHARED | 1)) {
 216                         _spin_lock_shared_contested(spin, ident);
 217                 }
 218         }
 219 #ifdef DEBUG_LOCKS
 220         int i;
 221         for (i = 0; i < SPINLOCK_DEBUG_ARRAY_SIZE; i++) {
 222                 if (gd->gd_curthread->td_spinlock_stack_id[i] == 0) {
 223                         gd->gd_curthread->td_spinlock_stack_id[i] = 1;
 224                         gd->gd_curthread->td_spinlock_stack[i] = spin;
 225                         gd->gd_curthread->td_spinlock_caller_pc[i] =
 226                                 __builtin_return_address(0);
 227                         break;
 228                 }
 229         }
 230 #endif
 231 }
 232
 233 /*
 234  * Unlock a shared lock.  For convenience we allow the last transition
 235  * to be to (SPINLOCK_SHARED|0), leaving the SPINLOCK_SHARED bit set
 236  * with a count to 0 which will optimize the next shared lock obtained.
 237  *
 238  * WARNING! In order to implement shared and exclusive spinlocks, an
 239  *          exclusive request will convert a multiply-held shared lock
 240  *          to exclusive and wait for shared holders to unlock.  So keep
 241  *          in mind that as of now the spinlock could actually be in an
 242  *          exclusive state.
 243  */
 244 static __inline void
 245 spin_unlock_shared_quick(globaldata_t gd, struct spinlock *spin)
 246 {
 247 #ifdef DEBUG_LOCKS
 248         int i;
 249         for (i = 0; i < SPINLOCK_DEBUG_ARRAY_SIZE; i++) {
 250                 if ((gd->gd_curthread->td_spinlock_stack_id[i] == 1) &&
 251                     (gd->gd_curthread->td_spinlock_stack[i] == spin)) {
 252                         gd->gd_curthread->td_spinlock_stack_id[i] = 0;
 253                         gd->gd_curthread->td_spinlock_stack[i] = NULL;
 254                         gd->gd_curthread->td_spinlock_caller_pc[i] = NULL;
 255                         break;
 256                 }
 257         }
 258 #endif
 259 #ifdef DEBUG_LOCKS
 260         KKASSERT(spin->lock != 0);
 261 #endif
 262         cpu_sfence();
 263         atomic_add_int(&spin->lock, -1);
 264
 265 #ifdef DEBUG_LOCKS
 266         KKASSERT(gd->gd_spinlocks > 0);
 267 #endif
 268         cpu_ccfence();
 269         --gd->gd_spinlocks;
 270         crit_exit_quick(gd->gd_curthread);
 271 }
 272
 273 static __inline void
 274 _spin_lock_shared(struct spinlock *spin, const char *ident)
 275 {
 276         _spin_lock_shared_quick(mycpu, spin, ident);
 277 }
 278
 279 static __inline void
 280 spin_unlock_shared(struct spinlock *spin)
 281 {
 282         spin_unlock_shared_quick(mycpu, spin);
 283 }
 284
 285 /*
 286  * Attempt to upgrade a shared spinlock to exclusive.  Return non-zero
 287  * on success, 0 on failure.
 288  */
 289 static __inline int
 290 spin_lock_upgrade_try(struct spinlock *spin)
 291 {
 292         if (atomic_cmpset_int(&spin->lock, SPINLOCK_SHARED|1, 1))
 293                 return 1;
 294         else
 295                 return 0;
 296 }
 297
 298 static __inline void
 299 spin_init(struct spinlock *spin, const char *descr __unused)
 300 {
 301         spin->lock = 0;
 302         spin->update = 0;
 303 #if 0
 304         spin->descr  = descr;
 305 #endif
 306 }
 307
 308 static __inline void
 309 spin_uninit(struct spinlock *spin)
 310 {
 311         /* unused */
 312 }
 313
 314 /*
 315  * SMP friendly update counter support.  Allows protected structures to
 316  * be accessed and retried without dirtying the cache line.  Retries if
 317  * modified, gains shared spin-lock if modification is underway.
 318  *
 319  * The returned value from spin_access_start() must be passed into
 320  * spin_access_end().
 321  */
 322 static __inline int
 323 spin_access_start(struct spinlock *spin)
 324 {
 325         int v;
 326
 327         v = *(volatile int *)&spin->update;
 328         cpu_lfence();
 329         if (__predict_false(v & 1))
 330                 spin_lock_shared(spin);
 331         return v;
 332 }
 333
 334 static __inline int
 335 spin_access_end(struct spinlock *spin, int v)
 336 {
 337         if (__predict_false(v & 1)) {
 338                 spin_unlock_shared(spin);
 339                 return 0;
 340         }
 341         cpu_lfence();
 342         return(*(volatile int *)&spin->update != v);
 343 }
 344
 345 static __inline void
 346 spin_lock_update(struct spinlock *spin)
 347 {
 348         spin_lock(spin);
 349         atomic_add_int_nonlocked(&spin->update, 1);
 350         cpu_sfence();
 351         KKASSERT_UNSPIN((spin->update & 1), spin);
 352 }
 353
 354 static __inline void
 355 spin_unlock_update(struct spinlock *spin)
 356 {
 357         cpu_sfence();
 358         atomic_add_int_nonlocked(&spin->update, 1);
 359         KKASSERT_UNSPIN(((spin->update & 1) == 0), spin);
 360         spin_unlock(spin);
 361 }
 362
 363 /*
 364  * API that doesn't integrate the acquisition of the spin-lock
 365  */
 366 static __inline int
 367 spin_access_start_only(struct spinlock *spin)
 368 {
 369         int v;
 370
 371         v = *(volatile int *)&spin->update;
 372         cpu_lfence();
 373
 374         return v;
 375 }
 376
 377 static __inline int
 378 spin_access_check_inprog(int v)
 379 {
 380         return (v & 1);
 381 }
 382
 383 static __inline int
 384 spin_access_end_only(struct spinlock *spin, int v)
 385 {
 386         cpu_lfence();
 387         return(*(volatile int *)&spin->update != v);
 388 }
 389
 390 static __inline void
 391 spin_lock_update_only(struct spinlock *spin)
 392 {
 393         atomic_add_int_nonlocked(&spin->update, 1);
 394         cpu_sfence();
 395         KKASSERT(spin->update & 1);
 396 }
 397
 398 static __inline void
 399 spin_unlock_update_only(struct spinlock *spin)
 400 {
 401         cpu_sfence();
 402         atomic_add_int_nonlocked(&spin->update, 1);
 403         KKASSERT((spin->update & 1) == 0);
 404 }
 405
 406 #endif  /* _SYS_SPINLOCK2_H_ */