| 1 | /* $NetBSD: linux_ww_mutex.c,v 1.2 2015/05/21 21:55:55 riastradh Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2014 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by Taylor R. Campbell. |
| 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 | #include <sys/cdefs.h> |
| 33 | __KERNEL_RCSID(0, "$NetBSD: linux_ww_mutex.c,v 1.2 2015/05/21 21:55:55 riastradh Exp $" ); |
| 34 | |
| 35 | #include <sys/types.h> |
| 36 | #include <sys/atomic.h> |
| 37 | #include <sys/condvar.h> |
| 38 | #include <sys/lockdebug.h> |
| 39 | #include <sys/lwp.h> |
| 40 | #include <sys/mutex.h> |
| 41 | #include <sys/rbtree.h> |
| 42 | |
| 43 | #include <linux/ww_mutex.h> |
| 44 | |
| 45 | #define WW_WANTLOCK(WW) \ |
| 46 | LOCKDEBUG_WANTLOCK((WW)->wwm_debug, (WW), \ |
| 47 | (uintptr_t)__builtin_return_address(0), 0) |
| 48 | #define WW_LOCKED(WW) \ |
| 49 | LOCKDEBUG_LOCKED((WW)->wwm_debug, (WW), NULL, \ |
| 50 | (uintptr_t)__builtin_return_address(0), 0) |
| 51 | #define WW_UNLOCKED(WW) \ |
| 52 | LOCKDEBUG_UNLOCKED((WW)->wwm_debug, (WW), \ |
| 53 | (uintptr_t)__builtin_return_address(0), 0) |
| 54 | |
| 55 | static int |
| 56 | ww_acquire_ctx_compare(void *cookie __unused, const void *va, const void *vb) |
| 57 | { |
| 58 | const struct ww_acquire_ctx *const ctx_a = va; |
| 59 | const struct ww_acquire_ctx *const ctx_b = vb; |
| 60 | |
| 61 | if (ctx_a->wwx_ticket < ctx_b->wwx_ticket) |
| 62 | return -1; |
| 63 | if (ctx_a->wwx_ticket > ctx_b->wwx_ticket) |
| 64 | return -1; |
| 65 | return 0; |
| 66 | } |
| 67 | |
| 68 | static int |
| 69 | ww_acquire_ctx_compare_key(void *cookie __unused, const void *vn, |
| 70 | const void *vk) |
| 71 | { |
| 72 | const struct ww_acquire_ctx *const ctx = vn; |
| 73 | const uint64_t *const ticketp = vk, ticket = *ticketp; |
| 74 | |
| 75 | if (ctx->wwx_ticket < ticket) |
| 76 | return -1; |
| 77 | if (ctx->wwx_ticket > ticket) |
| 78 | return -1; |
| 79 | return 0; |
| 80 | } |
| 81 | |
| 82 | static const rb_tree_ops_t ww_acquire_ctx_rb_ops = { |
| 83 | .rbto_compare_nodes = &ww_acquire_ctx_compare, |
| 84 | .rbto_compare_key = &ww_acquire_ctx_compare_key, |
| 85 | .rbto_node_offset = offsetof(struct ww_acquire_ctx, wwx_rb_node), |
| 86 | .rbto_context = NULL, |
| 87 | }; |
| 88 | |
| 89 | void |
| 90 | ww_acquire_init(struct ww_acquire_ctx *ctx, struct ww_class *class) |
| 91 | { |
| 92 | |
| 93 | ctx->wwx_class = class; |
| 94 | ctx->wwx_owner = curlwp; |
| 95 | ctx->wwx_ticket = atomic_inc_64_nv(&class->wwc_ticket); |
| 96 | ctx->wwx_acquired = 0; |
| 97 | ctx->wwx_acquire_done = false; |
| 98 | } |
| 99 | |
| 100 | void |
| 101 | ww_acquire_done(struct ww_acquire_ctx *ctx) |
| 102 | { |
| 103 | |
| 104 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 105 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 106 | |
| 107 | ctx->wwx_acquire_done = true; |
| 108 | } |
| 109 | |
| 110 | void |
| 111 | ww_acquire_fini(struct ww_acquire_ctx *ctx) |
| 112 | { |
| 113 | |
| 114 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 115 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 116 | KASSERTMSG((ctx->wwx_acquired == 0), "ctx %p still holds %u locks" , |
| 117 | ctx, ctx->wwx_acquired); |
| 118 | |
| 119 | ctx->wwx_acquired = ~0U; /* Fail if called again. */ |
| 120 | ctx->wwx_owner = NULL; |
| 121 | } |
| 122 | |
| 123 | #ifdef LOCKDEBUG |
| 124 | static void |
| 125 | ww_dump(volatile void *cookie) |
| 126 | { |
| 127 | volatile struct ww_mutex *mutex = cookie; |
| 128 | |
| 129 | printf_nolog("%-13s: " , "state" ); |
| 130 | switch (mutex->wwm_state) { |
| 131 | case WW_UNLOCKED: |
| 132 | printf_nolog("unlocked\n" ); |
| 133 | break; |
| 134 | case WW_OWNED: |
| 135 | printf_nolog("owned by lwp\n" ); |
| 136 | printf_nolog("%-13s: %p\n" , "owner" , mutex->wwm_u.owner); |
| 137 | printf_nolog("%-13s: %s\n" , "waiters" , |
| 138 | cv_has_waiters(__UNVOLATILE(&mutex->wwm_cv)) |
| 139 | ? "yes" : "no" ); |
| 140 | break; |
| 141 | case WW_CTX: |
| 142 | printf_nolog("owned via ctx\n" ); |
| 143 | printf_nolog("%-13s: %p\n" , "context" , mutex->wwm_u.ctx); |
| 144 | printf_nolog("%-13s: %p\n" , "lwp" , |
| 145 | mutex->wwm_u.ctx->wwx_owner); |
| 146 | printf_nolog("%-13s: %s\n" , "waiters" , |
| 147 | cv_has_waiters(__UNVOLATILE(&mutex->wwm_cv)) |
| 148 | ? "yes" : "no" ); |
| 149 | break; |
| 150 | case WW_WANTOWN: |
| 151 | printf_nolog("owned via ctx\n" ); |
| 152 | printf_nolog("%-13s: %p\n" , "context" , mutex->wwm_u.ctx); |
| 153 | printf_nolog("%-13s: %p\n" , "lwp" , |
| 154 | mutex->wwm_u.ctx->wwx_owner); |
| 155 | printf_nolog("%-13s: %s\n" , "waiters" , "yes (noctx)" ); |
| 156 | break; |
| 157 | default: |
| 158 | printf_nolog("unknown\n" ); |
| 159 | break; |
| 160 | } |
| 161 | } |
| 162 | |
| 163 | static lockops_t ww_lockops = { |
| 164 | .lo_name = "Wait/wound mutex" , |
| 165 | .lo_type = LOCKOPS_SLEEP, |
| 166 | .lo_dump = ww_dump, |
| 167 | }; |
| 168 | #endif |
| 169 | |
| 170 | void |
| 171 | ww_mutex_init(struct ww_mutex *mutex, struct ww_class *class) |
| 172 | { |
| 173 | |
| 174 | /* |
| 175 | * XXX Apparently Linux takes these with spin locks held. That |
| 176 | * strikes me as a bad idea, but so it is... |
| 177 | */ |
| 178 | mutex_init(&mutex->wwm_lock, MUTEX_DEFAULT, IPL_VM); |
| 179 | mutex->wwm_state = WW_UNLOCKED; |
| 180 | mutex->wwm_class = class; |
| 181 | rb_tree_init(&mutex->wwm_waiters, &ww_acquire_ctx_rb_ops); |
| 182 | cv_init(&mutex->wwm_cv, "linuxwwm" ); |
| 183 | #ifdef LOCKDEBUG |
| 184 | mutex->wwm_debug = LOCKDEBUG_ALLOC(mutex, &ww_lockops, |
| 185 | (uintptr_t)__builtin_return_address(0)); |
| 186 | #endif |
| 187 | } |
| 188 | |
| 189 | void |
| 190 | ww_mutex_destroy(struct ww_mutex *mutex) |
| 191 | { |
| 192 | |
| 193 | KASSERT(mutex->wwm_state == WW_UNLOCKED); |
| 194 | |
| 195 | #ifdef LOCKDEBUG |
| 196 | LOCKDEBUG_FREE(mutex->wwm_debug, mutex); |
| 197 | #endif |
| 198 | cv_destroy(&mutex->wwm_cv); |
| 199 | #if 0 |
| 200 | rb_tree_destroy(&mutex->wwm_waiters, &ww_acquire_ctx_rb_ops); |
| 201 | #endif |
| 202 | KASSERT(mutex->wwm_state == WW_UNLOCKED); |
| 203 | mutex_destroy(&mutex->wwm_lock); |
| 204 | } |
| 205 | |
| 206 | /* |
| 207 | * XXX WARNING: This returns true if it is locked by ANYONE. Does not |
| 208 | * mean `Do I hold this lock?' (answering which really requires an |
| 209 | * acquire context). |
| 210 | */ |
| 211 | bool |
| 212 | ww_mutex_is_locked(struct ww_mutex *mutex) |
| 213 | { |
| 214 | int locked; |
| 215 | |
| 216 | mutex_enter(&mutex->wwm_lock); |
| 217 | switch (mutex->wwm_state) { |
| 218 | case WW_UNLOCKED: |
| 219 | locked = false; |
| 220 | break; |
| 221 | case WW_OWNED: |
| 222 | case WW_CTX: |
| 223 | case WW_WANTOWN: |
| 224 | locked = true; |
| 225 | break; |
| 226 | default: |
| 227 | panic("wait/wound mutex %p in bad state: %d" , mutex, |
| 228 | (int)mutex->wwm_state); |
| 229 | } |
| 230 | mutex_exit(&mutex->wwm_lock); |
| 231 | |
| 232 | return locked; |
| 233 | } |
| 234 | |
| 235 | static void |
| 236 | ww_mutex_state_wait(struct ww_mutex *mutex, enum ww_mutex_state state) |
| 237 | { |
| 238 | |
| 239 | KASSERT(mutex->wwm_state == state); |
| 240 | do cv_wait(&mutex->wwm_cv, &mutex->wwm_lock); |
| 241 | while (mutex->wwm_state == state); |
| 242 | } |
| 243 | |
| 244 | static int |
| 245 | ww_mutex_state_wait_sig(struct ww_mutex *mutex, enum ww_mutex_state state) |
| 246 | { |
| 247 | int ret; |
| 248 | |
| 249 | KASSERT(mutex->wwm_state == state); |
| 250 | do { |
| 251 | /* XXX errno NetBSD->Linux */ |
| 252 | ret = -cv_wait_sig(&mutex->wwm_cv, &mutex->wwm_lock); |
| 253 | if (ret) |
| 254 | break; |
| 255 | } while (mutex->wwm_state == state); |
| 256 | |
| 257 | return ret; |
| 258 | } |
| 259 | |
| 260 | static void |
| 261 | ww_mutex_lock_wait(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx) |
| 262 | { |
| 263 | struct ww_acquire_ctx *collision __diagused; |
| 264 | |
| 265 | KASSERT(mutex_owned(&mutex->wwm_lock)); |
| 266 | |
| 267 | KASSERT((mutex->wwm_state == WW_CTX) || |
| 268 | (mutex->wwm_state == WW_WANTOWN)); |
| 269 | KASSERT(mutex->wwm_u.ctx != ctx); |
| 270 | KASSERTMSG((ctx->wwx_class == mutex->wwm_u.ctx->wwx_class), |
| 271 | "ww mutex class mismatch: %p != %p" , |
| 272 | ctx->wwx_class, mutex->wwm_u.ctx->wwx_class); |
| 273 | KASSERTMSG((mutex->wwm_u.ctx->wwx_ticket != ctx->wwx_ticket), |
| 274 | "ticket number reused: %" PRId64" (%p) %" PRId64" (%p)" , |
| 275 | ctx->wwx_ticket, ctx, |
| 276 | mutex->wwm_u.ctx->wwx_ticket, mutex->wwm_u.ctx); |
| 277 | |
| 278 | collision = rb_tree_insert_node(&mutex->wwm_waiters, ctx); |
| 279 | KASSERTMSG((collision == ctx), |
| 280 | "ticket number reused: %" PRId64" (%p) %" PRId64" (%p)" , |
| 281 | ctx->wwx_ticket, ctx, collision->wwx_ticket, collision); |
| 282 | |
| 283 | do cv_wait(&mutex->wwm_cv, &mutex->wwm_lock); |
| 284 | while (!(((mutex->wwm_state == WW_CTX) || |
| 285 | (mutex->wwm_state == WW_WANTOWN)) && |
| 286 | (mutex->wwm_u.ctx == ctx))); |
| 287 | |
| 288 | rb_tree_remove_node(&mutex->wwm_waiters, ctx); |
| 289 | } |
| 290 | |
| 291 | static int |
| 292 | ww_mutex_lock_wait_sig(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx) |
| 293 | { |
| 294 | struct ww_acquire_ctx *collision __diagused; |
| 295 | int ret; |
| 296 | |
| 297 | KASSERT(mutex_owned(&mutex->wwm_lock)); |
| 298 | |
| 299 | KASSERT((mutex->wwm_state == WW_CTX) || |
| 300 | (mutex->wwm_state == WW_WANTOWN)); |
| 301 | KASSERT(mutex->wwm_u.ctx != ctx); |
| 302 | KASSERTMSG((ctx->wwx_class == mutex->wwm_u.ctx->wwx_class), |
| 303 | "ww mutex class mismatch: %p != %p" , |
| 304 | ctx->wwx_class, mutex->wwm_u.ctx->wwx_class); |
| 305 | KASSERTMSG((mutex->wwm_u.ctx->wwx_ticket != ctx->wwx_ticket), |
| 306 | "ticket number reused: %" PRId64" (%p) %" PRId64" (%p)" , |
| 307 | ctx->wwx_ticket, ctx, |
| 308 | mutex->wwm_u.ctx->wwx_ticket, mutex->wwm_u.ctx); |
| 309 | |
| 310 | collision = rb_tree_insert_node(&mutex->wwm_waiters, ctx); |
| 311 | KASSERTMSG((collision == ctx), |
| 312 | "ticket number reused: %" PRId64" (%p) %" PRId64" (%p)" , |
| 313 | ctx->wwx_ticket, ctx, collision->wwx_ticket, collision); |
| 314 | |
| 315 | do { |
| 316 | /* XXX errno NetBSD->Linux */ |
| 317 | ret = -cv_wait_sig(&mutex->wwm_cv, &mutex->wwm_lock); |
| 318 | if (ret) |
| 319 | goto out; |
| 320 | } while (!(((mutex->wwm_state == WW_CTX) || |
| 321 | (mutex->wwm_state == WW_WANTOWN)) && |
| 322 | (mutex->wwm_u.ctx == ctx))); |
| 323 | |
| 324 | out: rb_tree_remove_node(&mutex->wwm_waiters, ctx); |
| 325 | return ret; |
| 326 | } |
| 327 | |
| 328 | static void |
| 329 | ww_mutex_lock_noctx(struct ww_mutex *mutex) |
| 330 | { |
| 331 | |
| 332 | mutex_enter(&mutex->wwm_lock); |
| 333 | retry: switch (mutex->wwm_state) { |
| 334 | case WW_UNLOCKED: |
| 335 | mutex->wwm_state = WW_OWNED; |
| 336 | mutex->wwm_u.owner = curlwp; |
| 337 | WW_LOCKED(mutex); |
| 338 | break; |
| 339 | case WW_OWNED: |
| 340 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 341 | "locking %p against myself: %p" , mutex, curlwp); |
| 342 | ww_mutex_state_wait(mutex, WW_OWNED); |
| 343 | goto retry; |
| 344 | case WW_CTX: |
| 345 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 346 | mutex->wwm_state = WW_WANTOWN; |
| 347 | /* FALLTHROUGH */ |
| 348 | case WW_WANTOWN: |
| 349 | KASSERTMSG((mutex->wwm_u.ctx->wwx_owner != curlwp), |
| 350 | "locking %p against myself: %p" , mutex, curlwp); |
| 351 | ww_mutex_state_wait(mutex, WW_WANTOWN); |
| 352 | goto retry; |
| 353 | default: |
| 354 | panic("wait/wound mutex %p in bad state: %d" , |
| 355 | mutex, (int)mutex->wwm_state); |
| 356 | } |
| 357 | KASSERT(mutex->wwm_state == WW_OWNED); |
| 358 | KASSERT(mutex->wwm_u.owner == curlwp); |
| 359 | mutex_exit(&mutex->wwm_lock); |
| 360 | } |
| 361 | |
| 362 | static int |
| 363 | ww_mutex_lock_noctx_sig(struct ww_mutex *mutex) |
| 364 | { |
| 365 | int ret; |
| 366 | |
| 367 | mutex_enter(&mutex->wwm_lock); |
| 368 | retry: switch (mutex->wwm_state) { |
| 369 | case WW_UNLOCKED: |
| 370 | mutex->wwm_state = WW_OWNED; |
| 371 | mutex->wwm_u.owner = curlwp; |
| 372 | WW_LOCKED(mutex); |
| 373 | break; |
| 374 | case WW_OWNED: |
| 375 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 376 | "locking %p against myself: %p" , mutex, curlwp); |
| 377 | ret = ww_mutex_state_wait_sig(mutex, WW_OWNED); |
| 378 | if (ret) |
| 379 | goto out; |
| 380 | goto retry; |
| 381 | case WW_CTX: |
| 382 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 383 | mutex->wwm_state = WW_WANTOWN; |
| 384 | /* FALLTHROUGH */ |
| 385 | case WW_WANTOWN: |
| 386 | KASSERTMSG((mutex->wwm_u.ctx->wwx_owner != curlwp), |
| 387 | "locking %p against myself: %p" , mutex, curlwp); |
| 388 | ret = ww_mutex_state_wait_sig(mutex, WW_WANTOWN); |
| 389 | if (ret) |
| 390 | goto out; |
| 391 | goto retry; |
| 392 | default: |
| 393 | panic("wait/wound mutex %p in bad state: %d" , |
| 394 | mutex, (int)mutex->wwm_state); |
| 395 | } |
| 396 | KASSERT(mutex->wwm_state == WW_OWNED); |
| 397 | KASSERT(mutex->wwm_u.owner == curlwp); |
| 398 | ret = 0; |
| 399 | out: mutex_exit(&mutex->wwm_lock); |
| 400 | return ret; |
| 401 | } |
| 402 | |
| 403 | int |
| 404 | ww_mutex_lock(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx) |
| 405 | { |
| 406 | |
| 407 | /* |
| 408 | * We do not WW_WANTLOCK at the beginning because we may |
| 409 | * correctly already hold it, if we have a context, in which |
| 410 | * case we must return EALREADY to the caller. |
| 411 | */ |
| 412 | ASSERT_SLEEPABLE(); |
| 413 | |
| 414 | if (ctx == NULL) { |
| 415 | WW_WANTLOCK(mutex); |
| 416 | ww_mutex_lock_noctx(mutex); |
| 417 | return 0; |
| 418 | } |
| 419 | |
| 420 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 421 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 422 | KASSERTMSG(!ctx->wwx_acquire_done, |
| 423 | "ctx %p done acquiring locks, can't acquire more" , ctx); |
| 424 | KASSERTMSG((ctx->wwx_acquired != ~0U), |
| 425 | "ctx %p finished, can't be used any more" , ctx); |
| 426 | KASSERTMSG((ctx->wwx_class == mutex->wwm_class), |
| 427 | "ctx %p in class %p, mutex %p in class %p" , |
| 428 | ctx, ctx->wwx_class, mutex, mutex->wwm_class); |
| 429 | |
| 430 | mutex_enter(&mutex->wwm_lock); |
| 431 | retry: switch (mutex->wwm_state) { |
| 432 | case WW_UNLOCKED: |
| 433 | WW_WANTLOCK(mutex); |
| 434 | mutex->wwm_state = WW_CTX; |
| 435 | mutex->wwm_u.ctx = ctx; |
| 436 | WW_LOCKED(mutex); |
| 437 | goto locked; |
| 438 | case WW_OWNED: |
| 439 | WW_WANTLOCK(mutex); |
| 440 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 441 | "locking %p against myself: %p" , mutex, curlwp); |
| 442 | ww_mutex_state_wait(mutex, WW_OWNED); |
| 443 | goto retry; |
| 444 | case WW_CTX: |
| 445 | break; |
| 446 | case WW_WANTOWN: |
| 447 | ww_mutex_state_wait(mutex, WW_WANTOWN); |
| 448 | goto retry; |
| 449 | default: |
| 450 | panic("wait/wound mutex %p in bad state: %d" , |
| 451 | mutex, (int)mutex->wwm_state); |
| 452 | } |
| 453 | |
| 454 | KASSERT(mutex->wwm_state == WW_CTX); |
| 455 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 456 | KASSERT((mutex->wwm_u.ctx == ctx) || |
| 457 | (mutex->wwm_u.ctx->wwx_owner != curlwp)); |
| 458 | |
| 459 | if (mutex->wwm_u.ctx == ctx) { |
| 460 | /* |
| 461 | * We already own it. Yes, this can happen correctly |
| 462 | * for objects whose locking order is determined by |
| 463 | * userland. |
| 464 | */ |
| 465 | mutex_exit(&mutex->wwm_lock); |
| 466 | return -EALREADY; |
| 467 | } |
| 468 | |
| 469 | /* |
| 470 | * We do not own it. We can safely assert to LOCKDEBUG that we |
| 471 | * want it. |
| 472 | */ |
| 473 | WW_WANTLOCK(mutex); |
| 474 | |
| 475 | if (mutex->wwm_u.ctx->wwx_ticket < ctx->wwx_ticket) { |
| 476 | /* |
| 477 | * Owned by a higher-priority party. Tell the caller |
| 478 | * to unlock everything and start over. |
| 479 | */ |
| 480 | KASSERTMSG((ctx->wwx_class == mutex->wwm_u.ctx->wwx_class), |
| 481 | "ww mutex class mismatch: %p != %p" , |
| 482 | ctx->wwx_class, mutex->wwm_u.ctx->wwx_class); |
| 483 | mutex_exit(&mutex->wwm_lock); |
| 484 | return -EDEADLK; |
| 485 | } |
| 486 | |
| 487 | /* |
| 488 | * Owned by a lower-priority party. Ask that party to wake us |
| 489 | * when it is done or it realizes it needs to back off. |
| 490 | */ |
| 491 | ww_mutex_lock_wait(mutex, ctx); |
| 492 | |
| 493 | locked: ctx->wwx_acquired++; |
| 494 | KASSERT((mutex->wwm_state == WW_CTX) || |
| 495 | (mutex->wwm_state == WW_WANTOWN)); |
| 496 | KASSERT(mutex->wwm_u.ctx == ctx); |
| 497 | mutex_exit(&mutex->wwm_lock); |
| 498 | return 0; |
| 499 | } |
| 500 | |
| 501 | int |
| 502 | ww_mutex_lock_interruptible(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx) |
| 503 | { |
| 504 | int ret; |
| 505 | |
| 506 | /* |
| 507 | * We do not WW_WANTLOCK at the beginning because we may |
| 508 | * correctly already hold it, if we have a context, in which |
| 509 | * case we must return EALREADY to the caller. |
| 510 | */ |
| 511 | ASSERT_SLEEPABLE(); |
| 512 | |
| 513 | if (ctx == NULL) { |
| 514 | WW_WANTLOCK(mutex); |
| 515 | return ww_mutex_lock_noctx_sig(mutex); |
| 516 | } |
| 517 | |
| 518 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 519 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 520 | KASSERTMSG(!ctx->wwx_acquire_done, |
| 521 | "ctx %p done acquiring locks, can't acquire more" , ctx); |
| 522 | KASSERTMSG((ctx->wwx_acquired != ~0U), |
| 523 | "ctx %p finished, can't be used any more" , ctx); |
| 524 | KASSERTMSG((ctx->wwx_class == mutex->wwm_class), |
| 525 | "ctx %p in class %p, mutex %p in class %p" , |
| 526 | ctx, ctx->wwx_class, mutex, mutex->wwm_class); |
| 527 | |
| 528 | mutex_enter(&mutex->wwm_lock); |
| 529 | retry: switch (mutex->wwm_state) { |
| 530 | case WW_UNLOCKED: |
| 531 | WW_WANTLOCK(mutex); |
| 532 | mutex->wwm_state = WW_CTX; |
| 533 | mutex->wwm_u.ctx = ctx; |
| 534 | WW_LOCKED(mutex); |
| 535 | goto locked; |
| 536 | case WW_OWNED: |
| 537 | WW_WANTLOCK(mutex); |
| 538 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 539 | "locking %p against myself: %p" , mutex, curlwp); |
| 540 | ret = ww_mutex_state_wait_sig(mutex, WW_OWNED); |
| 541 | if (ret) |
| 542 | goto out; |
| 543 | goto retry; |
| 544 | case WW_CTX: |
| 545 | break; |
| 546 | case WW_WANTOWN: |
| 547 | ret = ww_mutex_state_wait_sig(mutex, WW_WANTOWN); |
| 548 | if (ret) |
| 549 | goto out; |
| 550 | goto retry; |
| 551 | default: |
| 552 | panic("wait/wound mutex %p in bad state: %d" , |
| 553 | mutex, (int)mutex->wwm_state); |
| 554 | } |
| 555 | |
| 556 | KASSERT(mutex->wwm_state == WW_CTX); |
| 557 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 558 | KASSERT((mutex->wwm_u.ctx == ctx) || |
| 559 | (mutex->wwm_u.ctx->wwx_owner != curlwp)); |
| 560 | |
| 561 | if (mutex->wwm_u.ctx == ctx) { |
| 562 | /* |
| 563 | * We already own it. Yes, this can happen correctly |
| 564 | * for objects whose locking order is determined by |
| 565 | * userland. |
| 566 | */ |
| 567 | mutex_exit(&mutex->wwm_lock); |
| 568 | return -EALREADY; |
| 569 | } |
| 570 | |
| 571 | /* |
| 572 | * We do not own it. We can safely assert to LOCKDEBUG that we |
| 573 | * want it. |
| 574 | */ |
| 575 | WW_WANTLOCK(mutex); |
| 576 | |
| 577 | if (mutex->wwm_u.ctx->wwx_ticket < ctx->wwx_ticket) { |
| 578 | /* |
| 579 | * Owned by a higher-priority party. Tell the caller |
| 580 | * to unlock everything and start over. |
| 581 | */ |
| 582 | KASSERTMSG((ctx->wwx_class == mutex->wwm_u.ctx->wwx_class), |
| 583 | "ww mutex class mismatch: %p != %p" , |
| 584 | ctx->wwx_class, mutex->wwm_u.ctx->wwx_class); |
| 585 | mutex_exit(&mutex->wwm_lock); |
| 586 | return -EDEADLK; |
| 587 | } |
| 588 | |
| 589 | /* |
| 590 | * Owned by a lower-priority party. Ask that party to wake us |
| 591 | * when it is done or it realizes it needs to back off. |
| 592 | */ |
| 593 | ret = ww_mutex_lock_wait_sig(mutex, ctx); |
| 594 | if (ret) |
| 595 | goto out; |
| 596 | |
| 597 | locked: KASSERT((mutex->wwm_state == WW_CTX) || |
| 598 | (mutex->wwm_state == WW_WANTOWN)); |
| 599 | KASSERT(mutex->wwm_u.ctx == ctx); |
| 600 | ctx->wwx_acquired++; |
| 601 | ret = 0; |
| 602 | out: mutex_exit(&mutex->wwm_lock); |
| 603 | return ret; |
| 604 | } |
| 605 | |
| 606 | void |
| 607 | ww_mutex_lock_slow(struct ww_mutex *mutex, struct ww_acquire_ctx *ctx) |
| 608 | { |
| 609 | |
| 610 | /* Caller must not try to lock against self here. */ |
| 611 | WW_WANTLOCK(mutex); |
| 612 | ASSERT_SLEEPABLE(); |
| 613 | |
| 614 | if (ctx == NULL) { |
| 615 | ww_mutex_lock_noctx(mutex); |
| 616 | return; |
| 617 | } |
| 618 | |
| 619 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 620 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 621 | KASSERTMSG(!ctx->wwx_acquire_done, |
| 622 | "ctx %p done acquiring locks, can't acquire more" , ctx); |
| 623 | KASSERTMSG((ctx->wwx_acquired != ~0U), |
| 624 | "ctx %p finished, can't be used any more" , ctx); |
| 625 | KASSERTMSG((ctx->wwx_acquired == 0), |
| 626 | "ctx %p still holds %u locks, not allowed in slow path" , |
| 627 | ctx, ctx->wwx_acquired); |
| 628 | KASSERTMSG((ctx->wwx_class == mutex->wwm_class), |
| 629 | "ctx %p in class %p, mutex %p in class %p" , |
| 630 | ctx, ctx->wwx_class, mutex, mutex->wwm_class); |
| 631 | |
| 632 | mutex_enter(&mutex->wwm_lock); |
| 633 | retry: switch (mutex->wwm_state) { |
| 634 | case WW_UNLOCKED: |
| 635 | mutex->wwm_state = WW_CTX; |
| 636 | mutex->wwm_u.ctx = ctx; |
| 637 | WW_LOCKED(mutex); |
| 638 | goto locked; |
| 639 | case WW_OWNED: |
| 640 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 641 | "locking %p against myself: %p" , mutex, curlwp); |
| 642 | ww_mutex_state_wait(mutex, WW_OWNED); |
| 643 | goto retry; |
| 644 | case WW_CTX: |
| 645 | break; |
| 646 | case WW_WANTOWN: |
| 647 | ww_mutex_state_wait(mutex, WW_WANTOWN); |
| 648 | goto retry; |
| 649 | default: |
| 650 | panic("wait/wound mutex %p in bad state: %d" , |
| 651 | mutex, (int)mutex->wwm_state); |
| 652 | } |
| 653 | |
| 654 | KASSERT(mutex->wwm_state == WW_CTX); |
| 655 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 656 | KASSERTMSG((mutex->wwm_u.ctx->wwx_owner != curlwp), |
| 657 | "locking %p against myself: %p" , mutex, curlwp); |
| 658 | |
| 659 | /* |
| 660 | * Owned by another party, of any priority. Ask that party to |
| 661 | * wake us when it's done. |
| 662 | */ |
| 663 | ww_mutex_lock_wait(mutex, ctx); |
| 664 | |
| 665 | locked: KASSERT((mutex->wwm_state == WW_CTX) || |
| 666 | (mutex->wwm_state == WW_WANTOWN)); |
| 667 | KASSERT(mutex->wwm_u.ctx == ctx); |
| 668 | ctx->wwx_acquired++; |
| 669 | mutex_exit(&mutex->wwm_lock); |
| 670 | } |
| 671 | |
| 672 | int |
| 673 | ww_mutex_lock_slow_interruptible(struct ww_mutex *mutex, |
| 674 | struct ww_acquire_ctx *ctx) |
| 675 | { |
| 676 | int ret; |
| 677 | |
| 678 | WW_WANTLOCK(mutex); |
| 679 | ASSERT_SLEEPABLE(); |
| 680 | |
| 681 | if (ctx == NULL) |
| 682 | return ww_mutex_lock_noctx_sig(mutex); |
| 683 | |
| 684 | KASSERTMSG((ctx->wwx_owner == curlwp), |
| 685 | "ctx %p owned by %p, not self (%p)" , ctx, ctx->wwx_owner, curlwp); |
| 686 | KASSERTMSG(!ctx->wwx_acquire_done, |
| 687 | "ctx %p done acquiring locks, can't acquire more" , ctx); |
| 688 | KASSERTMSG((ctx->wwx_acquired != ~0U), |
| 689 | "ctx %p finished, can't be used any more" , ctx); |
| 690 | KASSERTMSG((ctx->wwx_acquired == 0), |
| 691 | "ctx %p still holds %u locks, not allowed in slow path" , |
| 692 | ctx, ctx->wwx_acquired); |
| 693 | KASSERTMSG((ctx->wwx_class == mutex->wwm_class), |
| 694 | "ctx %p in class %p, mutex %p in class %p" , |
| 695 | ctx, ctx->wwx_class, mutex, mutex->wwm_class); |
| 696 | |
| 697 | mutex_enter(&mutex->wwm_lock); |
| 698 | retry: switch (mutex->wwm_state) { |
| 699 | case WW_UNLOCKED: |
| 700 | mutex->wwm_state = WW_CTX; |
| 701 | mutex->wwm_u.ctx = ctx; |
| 702 | WW_LOCKED(mutex); |
| 703 | goto locked; |
| 704 | case WW_OWNED: |
| 705 | KASSERTMSG((mutex->wwm_u.owner != curlwp), |
| 706 | "locking %p against myself: %p" , mutex, curlwp); |
| 707 | ret = ww_mutex_state_wait_sig(mutex, WW_OWNED); |
| 708 | if (ret) |
| 709 | goto out; |
| 710 | goto retry; |
| 711 | case WW_CTX: |
| 712 | break; |
| 713 | case WW_WANTOWN: |
| 714 | ret = ww_mutex_state_wait_sig(mutex, WW_WANTOWN); |
| 715 | if (ret) |
| 716 | goto out; |
| 717 | goto retry; |
| 718 | default: |
| 719 | panic("wait/wound mutex %p in bad state: %d" , |
| 720 | mutex, (int)mutex->wwm_state); |
| 721 | } |
| 722 | |
| 723 | KASSERT(mutex->wwm_state == WW_CTX); |
| 724 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 725 | KASSERTMSG((mutex->wwm_u.ctx->wwx_owner != curlwp), |
| 726 | "locking %p against myself: %p" , mutex, curlwp); |
| 727 | |
| 728 | /* |
| 729 | * Owned by another party, of any priority. Ask that party to |
| 730 | * wake us when it's done. |
| 731 | */ |
| 732 | ret = ww_mutex_lock_wait_sig(mutex, ctx); |
| 733 | if (ret) |
| 734 | goto out; |
| 735 | |
| 736 | locked: KASSERT((mutex->wwm_state == WW_CTX) || |
| 737 | (mutex->wwm_state == WW_WANTOWN)); |
| 738 | KASSERT(mutex->wwm_u.ctx == ctx); |
| 739 | ctx->wwx_acquired++; |
| 740 | ret = 0; |
| 741 | out: mutex_exit(&mutex->wwm_lock); |
| 742 | return ret; |
| 743 | } |
| 744 | |
| 745 | int |
| 746 | ww_mutex_trylock(struct ww_mutex *mutex) |
| 747 | { |
| 748 | int ret; |
| 749 | |
| 750 | mutex_enter(&mutex->wwm_lock); |
| 751 | if (mutex->wwm_state == WW_UNLOCKED) { |
| 752 | mutex->wwm_state = WW_OWNED; |
| 753 | mutex->wwm_u.owner = curlwp; |
| 754 | WW_WANTLOCK(mutex); |
| 755 | WW_LOCKED(mutex); |
| 756 | ret = 1; |
| 757 | } else { |
| 758 | KASSERTMSG(((mutex->wwm_state != WW_OWNED) || |
| 759 | (mutex->wwm_u.owner != curlwp)), |
| 760 | "locking %p against myself: %p" , mutex, curlwp); |
| 761 | KASSERTMSG(((mutex->wwm_state != WW_CTX) || |
| 762 | (mutex->wwm_u.ctx->wwx_owner != curlwp)), |
| 763 | "locking %p against myself: %p" , mutex, curlwp); |
| 764 | KASSERTMSG(((mutex->wwm_state != WW_WANTOWN) || |
| 765 | (mutex->wwm_u.ctx->wwx_owner != curlwp)), |
| 766 | "locking %p against myself: %p" , mutex, curlwp); |
| 767 | ret = 0; |
| 768 | } |
| 769 | mutex_exit(&mutex->wwm_lock); |
| 770 | |
| 771 | return ret; |
| 772 | } |
| 773 | |
| 774 | static void |
| 775 | ww_mutex_unlock_release(struct ww_mutex *mutex) |
| 776 | { |
| 777 | |
| 778 | KASSERT(mutex_owned(&mutex->wwm_lock)); |
| 779 | KASSERT((mutex->wwm_state == WW_CTX) || |
| 780 | (mutex->wwm_state == WW_WANTOWN)); |
| 781 | KASSERT(mutex->wwm_u.ctx != NULL); |
| 782 | KASSERTMSG((mutex->wwm_u.ctx->wwx_owner == curlwp), |
| 783 | "ww_mutex %p ctx %p held by %p, not by self (%p)" , |
| 784 | mutex, mutex->wwm_u.ctx, mutex->wwm_u.ctx->wwx_owner, |
| 785 | curlwp); |
| 786 | KASSERT(mutex->wwm_u.ctx->wwx_acquired != ~0U); |
| 787 | mutex->wwm_u.ctx->wwx_acquired--; |
| 788 | mutex->wwm_u.ctx = NULL; |
| 789 | } |
| 790 | |
| 791 | void |
| 792 | ww_mutex_unlock(struct ww_mutex *mutex) |
| 793 | { |
| 794 | struct ww_acquire_ctx *ctx; |
| 795 | |
| 796 | mutex_enter(&mutex->wwm_lock); |
| 797 | KASSERT(mutex->wwm_state != WW_UNLOCKED); |
| 798 | switch (mutex->wwm_state) { |
| 799 | case WW_UNLOCKED: |
| 800 | panic("unlocking unlocked wait/wound mutex: %p" , mutex); |
| 801 | case WW_OWNED: |
| 802 | /* Let the context lockers fight over it. */ |
| 803 | mutex->wwm_u.owner = NULL; |
| 804 | mutex->wwm_state = WW_UNLOCKED; |
| 805 | break; |
| 806 | case WW_CTX: |
| 807 | ww_mutex_unlock_release(mutex); |
| 808 | /* |
| 809 | * If there are any waiters with contexts, grant the |
| 810 | * lock to the highest-priority one. Otherwise, just |
| 811 | * unlock it. |
| 812 | */ |
| 813 | if ((ctx = RB_TREE_MIN(&mutex->wwm_waiters)) != NULL) { |
| 814 | mutex->wwm_state = WW_CTX; |
| 815 | mutex->wwm_u.ctx = ctx; |
| 816 | } else { |
| 817 | mutex->wwm_state = WW_UNLOCKED; |
| 818 | } |
| 819 | break; |
| 820 | case WW_WANTOWN: |
| 821 | ww_mutex_unlock_release(mutex); |
| 822 | /* Let the non-context lockers fight over it. */ |
| 823 | mutex->wwm_state = WW_UNLOCKED; |
| 824 | break; |
| 825 | } |
| 826 | WW_UNLOCKED(mutex); |
| 827 | cv_broadcast(&mutex->wwm_cv); |
| 828 | mutex_exit(&mutex->wwm_lock); |
| 829 | } |
| 830 | |