| 1 | /* $NetBSD: kern_condvar.c,v 1.35 2015/08/07 06:22:12 uebayasi Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by Andrew Doran. |
| 9 | * |
| 10 | * Redistribution and use in source and binary forms, with or without |
| 11 | * modification, are permitted provided that the following conditions |
| 12 | * are met: |
| 13 | * 1. Redistributions of source code must retain the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer. |
| 15 | * 2. Redistributions in binary form must reproduce the above copyright |
| 16 | * notice, this list of conditions and the following disclaimer in the |
| 17 | * documentation and/or other materials provided with the distribution. |
| 18 | * |
| 19 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 20 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 21 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 23 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 29 | * POSSIBILITY OF SUCH DAMAGE. |
| 30 | */ |
| 31 | |
| 32 | /* |
| 33 | * Kernel condition variable implementation. |
| 34 | */ |
| 35 | |
| 36 | #include <sys/cdefs.h> |
| 37 | __KERNEL_RCSID(0, "$NetBSD: kern_condvar.c,v 1.35 2015/08/07 06:22:12 uebayasi Exp $" ); |
| 38 | |
| 39 | #include <sys/param.h> |
| 40 | #include <sys/systm.h> |
| 41 | #include <sys/lwp.h> |
| 42 | #include <sys/condvar.h> |
| 43 | #include <sys/sleepq.h> |
| 44 | #include <sys/lockdebug.h> |
| 45 | #include <sys/cpu.h> |
| 46 | |
| 47 | /* |
| 48 | * Accessors for the private contents of the kcondvar_t data type. |
| 49 | * |
| 50 | * cv_opaque[0] sleepq... |
| 51 | * cv_opaque[1] ...pointers |
| 52 | * cv_opaque[2] description for ps(1) |
| 53 | * |
| 54 | * cv_opaque[0..1] is protected by the interlock passed to cv_wait() (enqueue |
| 55 | * only), and the sleep queue lock acquired with sleeptab_lookup() (enqueue |
| 56 | * and dequeue). |
| 57 | * |
| 58 | * cv_opaque[2] (the wmesg) is static and does not change throughout the life |
| 59 | * of the CV. |
| 60 | */ |
| 61 | #define CV_SLEEPQ(cv) ((sleepq_t *)(cv)->cv_opaque) |
| 62 | #define CV_WMESG(cv) ((const char *)(cv)->cv_opaque[2]) |
| 63 | #define CV_SET_WMESG(cv, v) (cv)->cv_opaque[2] = __UNCONST(v) |
| 64 | |
| 65 | #define CV_DEBUG_P(cv) (CV_WMESG(cv) != nodebug) |
| 66 | #define CV_RA ((uintptr_t)__builtin_return_address(0)) |
| 67 | |
| 68 | static void cv_unsleep(lwp_t *, bool); |
| 69 | static void cv_wakeup_one(kcondvar_t *); |
| 70 | static void cv_wakeup_all(kcondvar_t *); |
| 71 | |
| 72 | static syncobj_t cv_syncobj = { |
| 73 | SOBJ_SLEEPQ_SORTED, |
| 74 | cv_unsleep, |
| 75 | sleepq_changepri, |
| 76 | sleepq_lendpri, |
| 77 | syncobj_noowner, |
| 78 | }; |
| 79 | |
| 80 | lockops_t cv_lockops = { |
| 81 | "Condition variable" , |
| 82 | LOCKOPS_CV, |
| 83 | NULL |
| 84 | }; |
| 85 | |
| 86 | static const char deadcv[] = "deadcv" ; |
| 87 | #ifdef LOCKDEBUG |
| 88 | static const char nodebug[] = "nodebug" ; |
| 89 | #endif |
| 90 | |
| 91 | /* |
| 92 | * cv_init: |
| 93 | * |
| 94 | * Initialize a condition variable for use. |
| 95 | */ |
| 96 | void |
| 97 | cv_init(kcondvar_t *cv, const char *wmesg) |
| 98 | { |
| 99 | #ifdef LOCKDEBUG |
| 100 | bool dodebug; |
| 101 | |
| 102 | dodebug = LOCKDEBUG_ALLOC(cv, &cv_lockops, |
| 103 | (uintptr_t)__builtin_return_address(0)); |
| 104 | if (!dodebug) { |
| 105 | /* XXX This will break vfs_lockf. */ |
| 106 | wmesg = nodebug; |
| 107 | } |
| 108 | #endif |
| 109 | KASSERT(wmesg != NULL); |
| 110 | CV_SET_WMESG(cv, wmesg); |
| 111 | sleepq_init(CV_SLEEPQ(cv)); |
| 112 | } |
| 113 | |
| 114 | /* |
| 115 | * cv_destroy: |
| 116 | * |
| 117 | * Tear down a condition variable. |
| 118 | */ |
| 119 | void |
| 120 | cv_destroy(kcondvar_t *cv) |
| 121 | { |
| 122 | |
| 123 | LOCKDEBUG_FREE(CV_DEBUG_P(cv), cv); |
| 124 | #ifdef DIAGNOSTIC |
| 125 | KASSERT(cv_is_valid(cv)); |
| 126 | CV_SET_WMESG(cv, deadcv); |
| 127 | #endif |
| 128 | } |
| 129 | |
| 130 | /* |
| 131 | * cv_enter: |
| 132 | * |
| 133 | * Look up and lock the sleep queue corresponding to the given |
| 134 | * condition variable, and increment the number of waiters. |
| 135 | */ |
| 136 | static inline void |
| 137 | cv_enter(kcondvar_t *cv, kmutex_t *mtx, lwp_t *l) |
| 138 | { |
| 139 | sleepq_t *sq; |
| 140 | kmutex_t *mp; |
| 141 | |
| 142 | KASSERT(cv_is_valid(cv)); |
| 143 | KASSERT(!cpu_intr_p()); |
| 144 | KASSERT((l->l_pflag & LP_INTR) == 0 || panicstr != NULL); |
| 145 | |
| 146 | LOCKDEBUG_LOCKED(CV_DEBUG_P(cv), cv, mtx, CV_RA, 0); |
| 147 | |
| 148 | l->l_kpriority = true; |
| 149 | mp = sleepq_hashlock(cv); |
| 150 | sq = CV_SLEEPQ(cv); |
| 151 | sleepq_enter(sq, l, mp); |
| 152 | sleepq_enqueue(sq, cv, CV_WMESG(cv), &cv_syncobj); |
| 153 | mutex_exit(mtx); |
| 154 | KASSERT(cv_has_waiters(cv)); |
| 155 | } |
| 156 | |
| 157 | /* |
| 158 | * cv_exit: |
| 159 | * |
| 160 | * After resuming execution, check to see if we have been restarted |
| 161 | * as a result of cv_signal(). If we have, but cannot take the |
| 162 | * wakeup (because of eg a pending Unix signal or timeout) then try |
| 163 | * to ensure that another LWP sees it. This is necessary because |
| 164 | * there may be multiple waiters, and at least one should take the |
| 165 | * wakeup if possible. |
| 166 | */ |
| 167 | static inline int |
| 168 | cv_exit(kcondvar_t *cv, kmutex_t *mtx, lwp_t *l, const int error) |
| 169 | { |
| 170 | |
| 171 | mutex_enter(mtx); |
| 172 | if (__predict_false(error != 0)) |
| 173 | cv_signal(cv); |
| 174 | |
| 175 | LOCKDEBUG_UNLOCKED(CV_DEBUG_P(cv), cv, CV_RA, 0); |
| 176 | KASSERT(cv_is_valid(cv)); |
| 177 | |
| 178 | return error; |
| 179 | } |
| 180 | |
| 181 | /* |
| 182 | * cv_unsleep: |
| 183 | * |
| 184 | * Remove an LWP from the condition variable and sleep queue. This |
| 185 | * is called when the LWP has not been awoken normally but instead |
| 186 | * interrupted: for example, when a signal is received. Must be |
| 187 | * called with the LWP locked, and must return it unlocked. |
| 188 | */ |
| 189 | static void |
| 190 | cv_unsleep(lwp_t *l, bool cleanup) |
| 191 | { |
| 192 | kcondvar_t *cv __diagused; |
| 193 | |
| 194 | cv = (kcondvar_t *)(uintptr_t)l->l_wchan; |
| 195 | |
| 196 | KASSERT(l->l_wchan == (wchan_t)cv); |
| 197 | KASSERT(l->l_sleepq == CV_SLEEPQ(cv)); |
| 198 | KASSERT(cv_is_valid(cv)); |
| 199 | KASSERT(cv_has_waiters(cv)); |
| 200 | |
| 201 | sleepq_unsleep(l, cleanup); |
| 202 | } |
| 203 | |
| 204 | /* |
| 205 | * cv_wait: |
| 206 | * |
| 207 | * Wait non-interruptably on a condition variable until awoken. |
| 208 | */ |
| 209 | void |
| 210 | cv_wait(kcondvar_t *cv, kmutex_t *mtx) |
| 211 | { |
| 212 | lwp_t *l = curlwp; |
| 213 | |
| 214 | KASSERT(mutex_owned(mtx)); |
| 215 | |
| 216 | cv_enter(cv, mtx, l); |
| 217 | (void)sleepq_block(0, false); |
| 218 | (void)cv_exit(cv, mtx, l, 0); |
| 219 | } |
| 220 | |
| 221 | /* |
| 222 | * cv_wait_sig: |
| 223 | * |
| 224 | * Wait on a condition variable until a awoken or a signal is received. |
| 225 | * Will also return early if the process is exiting. Returns zero if |
| 226 | * awoken normally, ERESTART if a signal was received and the system |
| 227 | * call is restartable, or EINTR otherwise. |
| 228 | */ |
| 229 | int |
| 230 | cv_wait_sig(kcondvar_t *cv, kmutex_t *mtx) |
| 231 | { |
| 232 | lwp_t *l = curlwp; |
| 233 | int error; |
| 234 | |
| 235 | KASSERT(mutex_owned(mtx)); |
| 236 | |
| 237 | cv_enter(cv, mtx, l); |
| 238 | error = sleepq_block(0, true); |
| 239 | return cv_exit(cv, mtx, l, error); |
| 240 | } |
| 241 | |
| 242 | /* |
| 243 | * cv_timedwait: |
| 244 | * |
| 245 | * Wait on a condition variable until awoken or the specified timeout |
| 246 | * expires. Returns zero if awoken normally or EWOULDBLOCK if the |
| 247 | * timeout expired. |
| 248 | * |
| 249 | * timo is a timeout in ticks. timo = 0 specifies an infinite timeout. |
| 250 | */ |
| 251 | int |
| 252 | cv_timedwait(kcondvar_t *cv, kmutex_t *mtx, int timo) |
| 253 | { |
| 254 | lwp_t *l = curlwp; |
| 255 | int error; |
| 256 | |
| 257 | KASSERT(mutex_owned(mtx)); |
| 258 | |
| 259 | cv_enter(cv, mtx, l); |
| 260 | error = sleepq_block(timo, false); |
| 261 | return cv_exit(cv, mtx, l, error); |
| 262 | } |
| 263 | |
| 264 | /* |
| 265 | * cv_timedwait_sig: |
| 266 | * |
| 267 | * Wait on a condition variable until a timeout expires, awoken or a |
| 268 | * signal is received. Will also return early if the process is |
| 269 | * exiting. Returns zero if awoken normally, EWOULDBLOCK if the |
| 270 | * timeout expires, ERESTART if a signal was received and the system |
| 271 | * call is restartable, or EINTR otherwise. |
| 272 | * |
| 273 | * timo is a timeout in ticks. timo = 0 specifies an infinite timeout. |
| 274 | */ |
| 275 | int |
| 276 | cv_timedwait_sig(kcondvar_t *cv, kmutex_t *mtx, int timo) |
| 277 | { |
| 278 | lwp_t *l = curlwp; |
| 279 | int error; |
| 280 | |
| 281 | KASSERT(mutex_owned(mtx)); |
| 282 | |
| 283 | cv_enter(cv, mtx, l); |
| 284 | error = sleepq_block(timo, true); |
| 285 | return cv_exit(cv, mtx, l, error); |
| 286 | } |
| 287 | |
| 288 | /* |
| 289 | * cv_signal: |
| 290 | * |
| 291 | * Wake the highest priority LWP waiting on a condition variable. |
| 292 | * Must be called with the interlocking mutex held. |
| 293 | */ |
| 294 | void |
| 295 | cv_signal(kcondvar_t *cv) |
| 296 | { |
| 297 | |
| 298 | /* LOCKDEBUG_WAKEUP(CV_DEBUG_P(cv), cv, CV_RA); */ |
| 299 | KASSERT(cv_is_valid(cv)); |
| 300 | |
| 301 | if (__predict_false(!TAILQ_EMPTY(CV_SLEEPQ(cv)))) |
| 302 | cv_wakeup_one(cv); |
| 303 | } |
| 304 | |
| 305 | static void __noinline |
| 306 | cv_wakeup_one(kcondvar_t *cv) |
| 307 | { |
| 308 | sleepq_t *sq; |
| 309 | kmutex_t *mp; |
| 310 | lwp_t *l; |
| 311 | |
| 312 | KASSERT(cv_is_valid(cv)); |
| 313 | |
| 314 | mp = sleepq_hashlock(cv); |
| 315 | sq = CV_SLEEPQ(cv); |
| 316 | l = TAILQ_FIRST(sq); |
| 317 | if (l == NULL) { |
| 318 | mutex_spin_exit(mp); |
| 319 | return; |
| 320 | } |
| 321 | KASSERT(l->l_sleepq == sq); |
| 322 | KASSERT(l->l_mutex == mp); |
| 323 | KASSERT(l->l_wchan == cv); |
| 324 | sleepq_remove(sq, l); |
| 325 | mutex_spin_exit(mp); |
| 326 | |
| 327 | KASSERT(cv_is_valid(cv)); |
| 328 | } |
| 329 | |
| 330 | /* |
| 331 | * cv_broadcast: |
| 332 | * |
| 333 | * Wake all LWPs waiting on a condition variable. Must be called |
| 334 | * with the interlocking mutex held. |
| 335 | */ |
| 336 | void |
| 337 | cv_broadcast(kcondvar_t *cv) |
| 338 | { |
| 339 | |
| 340 | /* LOCKDEBUG_WAKEUP(CV_DEBUG_P(cv), cv, CV_RA); */ |
| 341 | KASSERT(cv_is_valid(cv)); |
| 342 | |
| 343 | if (__predict_false(!TAILQ_EMPTY(CV_SLEEPQ(cv)))) |
| 344 | cv_wakeup_all(cv); |
| 345 | } |
| 346 | |
| 347 | static void __noinline |
| 348 | cv_wakeup_all(kcondvar_t *cv) |
| 349 | { |
| 350 | sleepq_t *sq; |
| 351 | kmutex_t *mp; |
| 352 | lwp_t *l, *next; |
| 353 | |
| 354 | KASSERT(cv_is_valid(cv)); |
| 355 | |
| 356 | mp = sleepq_hashlock(cv); |
| 357 | sq = CV_SLEEPQ(cv); |
| 358 | for (l = TAILQ_FIRST(sq); l != NULL; l = next) { |
| 359 | KASSERT(l->l_sleepq == sq); |
| 360 | KASSERT(l->l_mutex == mp); |
| 361 | KASSERT(l->l_wchan == cv); |
| 362 | next = TAILQ_NEXT(l, l_sleepchain); |
| 363 | sleepq_remove(sq, l); |
| 364 | } |
| 365 | mutex_spin_exit(mp); |
| 366 | |
| 367 | KASSERT(cv_is_valid(cv)); |
| 368 | } |
| 369 | |
| 370 | /* |
| 371 | * cv_has_waiters: |
| 372 | * |
| 373 | * For diagnostic assertions: return non-zero if a condition |
| 374 | * variable has waiters. |
| 375 | */ |
| 376 | bool |
| 377 | cv_has_waiters(kcondvar_t *cv) |
| 378 | { |
| 379 | |
| 380 | return !TAILQ_EMPTY(CV_SLEEPQ(cv)); |
| 381 | } |
| 382 | |
| 383 | /* |
| 384 | * cv_is_valid: |
| 385 | * |
| 386 | * For diagnostic assertions: return non-zero if a condition |
| 387 | * variable appears to be valid. No locks need be held. |
| 388 | */ |
| 389 | bool |
| 390 | cv_is_valid(kcondvar_t *cv) |
| 391 | { |
| 392 | |
| 393 | return CV_WMESG(cv) != deadcv && CV_WMESG(cv) != NULL; |
| 394 | } |
| 395 | |