1 /* $NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $ */ 2 3 /*- 4 * SPDX-License-Identifier: BSD-4-Clause 5 * 6 * Copyright (c) 2009-2016 Dmitry Chagin 7 * Copyright (c) 2005 Emmanuel Dreyfus 8 * All rights reserved. 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by Emmanuel Dreyfus 21 * 4. The name of the author may not be used to endorse or promote 22 * products derived from this software without specific prior written 23 * permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE THE AUTHOR AND CONTRIBUTORS ``AS IS'' 26 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 27 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS 29 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35 * POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 #if 0 41 __KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $"); 42 #endif 43 44 #include "opt_compat.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/imgact.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/lock.h> 52 #include <sys/malloc.h> 53 #include <sys/mutex.h> 54 #include <sys/priv.h> 55 #include <sys/proc.h> 56 #include <sys/queue.h> 57 #include <sys/sched.h> 58 #include <sys/sdt.h> 59 #include <sys/umtx.h> 60 61 #include <vm/vm_extern.h> 62 63 #ifdef COMPAT_LINUX32 64 #include <machine/../linux32/linux.h> 65 #include <machine/../linux32/linux32_proto.h> 66 #else 67 #include <machine/../linux/linux.h> 68 #include <machine/../linux/linux_proto.h> 69 #endif 70 #include <compat/linux/linux_dtrace.h> 71 #include <compat/linux/linux_emul.h> 72 #include <compat/linux/linux_futex.h> 73 #include <compat/linux/linux_timer.h> 74 #include <compat/linux/linux_util.h> 75 76 /* DTrace init */ 77 LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE); 78 79 /** 80 * Futex part for the special DTrace module "locks". 81 */ 82 LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, locked, "struct mtx *"); 83 LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, unlock, "struct mtx *"); 84 85 /** 86 * Per futex probes. 87 */ 88 LIN_SDT_PROBE_DEFINE1(futex, futex, create, "struct sx *"); 89 LIN_SDT_PROBE_DEFINE1(futex, futex, destroy, "struct sx *"); 90 91 /** 92 * DTrace probes in this module. 93 */ 94 LIN_SDT_PROBE_DEFINE3(futex, futex_put, destroy, "uint32_t *", "uint32_t", 95 "int"); 96 LIN_SDT_PROBE_DEFINE3(futex, futex_put, unlock, "uint32_t *", "uint32_t", 97 "int"); 98 LIN_SDT_PROBE_DEFINE1(futex, futex_get0, umtx_key_get_error, "int"); 99 LIN_SDT_PROBE_DEFINE3(futex, futex_get0, shared, "uint32_t *", "uint32_t", 100 "int"); 101 LIN_SDT_PROBE_DEFINE1(futex, futex_get0, null, "uint32_t *"); 102 LIN_SDT_PROBE_DEFINE3(futex, futex_get0, new, "uint32_t *", "uint32_t", "int"); 103 LIN_SDT_PROBE_DEFINE0(futex, futex_get, error); 104 LIN_SDT_PROBE_DEFINE5(futex, futex_sleep, requeue_error, "int", "uint32_t *", 105 "struct waiting_proc *", "uint32_t *", "uint32_t"); 106 LIN_SDT_PROBE_DEFINE3(futex, futex_sleep, sleep_error, "int", "uint32_t *", 107 "struct waiting_proc *"); 108 LIN_SDT_PROBE_DEFINE3(futex, futex_wake, iterate, "uint32_t", 109 "struct waiting_proc *", "uint32_t"); 110 LIN_SDT_PROBE_DEFINE1(futex, futex_wake, wakeup, "struct waiting_proc *"); 111 LIN_SDT_PROBE_DEFINE1(futex, futex_requeue, wakeup, "struct waiting_proc *"); 112 LIN_SDT_PROBE_DEFINE3(futex, futex_requeue, requeue, "uint32_t *", 113 "struct waiting_proc *", "uint32_t"); 114 LIN_SDT_PROBE_DEFINE1(futex, futex_wait, sleep_error, "int"); 115 LIN_SDT_PROBE_DEFINE4(futex, futex_atomic_op, decoded_op, "int", "int", "int", 116 "int"); 117 LIN_SDT_PROBE_DEFINE0(futex, futex_atomic_op, missing_access_check); 118 LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_op, "int"); 119 LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_cmp, "int"); 120 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_clockswitch); 121 LIN_SDT_PROBE_DEFINE1(futex, linux_futex, copyin_error, "int"); 122 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, invalid_cmp_requeue_use); 123 LIN_SDT_PROBE_DEFINE3(futex, linux_futex, debug_wait, "uint32_t *", 124 "uint32_t", "uint32_t"); 125 LIN_SDT_PROBE_DEFINE4(futex, linux_futex, debug_wait_value_neq, 126 "uint32_t *", "uint32_t", "int", "uint32_t"); 127 LIN_SDT_PROBE_DEFINE3(futex, linux_futex, debug_wake, "uint32_t *", 128 "uint32_t", "uint32_t"); 129 LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_cmp_requeue, "uint32_t *", 130 "uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *"); 131 LIN_SDT_PROBE_DEFINE2(futex, linux_futex, debug_cmp_requeue_value_neq, 132 "uint32_t", "int"); 133 LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_wake_op, "uint32_t *", 134 "int", "uint32_t", "uint32_t *", "uint32_t"); 135 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unhandled_efault); 136 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_lock_pi); 137 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_unlock_pi); 138 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_trylock_pi); 139 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, deprecated_requeue); 140 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_wait_requeue_pi); 141 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_cmp_requeue_pi); 142 LIN_SDT_PROBE_DEFINE1(futex, linux_futex, unknown_operation, "int"); 143 LIN_SDT_PROBE_DEFINE0(futex, linux_set_robust_list, size_error); 144 LIN_SDT_PROBE_DEFINE1(futex, linux_get_robust_list, copyout_error, "int"); 145 LIN_SDT_PROBE_DEFINE1(futex, handle_futex_death, copyin_error, "int"); 146 LIN_SDT_PROBE_DEFINE1(futex, fetch_robust_entry, copyin_error, "int"); 147 LIN_SDT_PROBE_DEFINE1(futex, release_futexes, copyin_error, "int"); 148 149 struct futex; 150 151 struct waiting_proc { 152 uint32_t wp_flags; 153 struct futex *wp_futex; 154 TAILQ_ENTRY(waiting_proc) wp_list; 155 }; 156 157 struct futex { 158 struct mtx f_lck; 159 uint32_t *f_uaddr; /* user-supplied value, for debug */ 160 struct umtx_key f_key; 161 uint32_t f_refcount; 162 uint32_t f_bitset; 163 LIST_ENTRY(futex) f_list; 164 TAILQ_HEAD(lf_waiting_proc, waiting_proc) f_waiting_proc; 165 }; 166 167 #define FUTEX_LOCK(f) mtx_lock(&(f)->f_lck) 168 #define FUTEX_LOCKED(f) mtx_owned(&(f)->f_lck) 169 #define FUTEX_UNLOCK(f) mtx_unlock(&(f)->f_lck) 170 #define FUTEX_INIT(f) do { \ 171 mtx_init(&(f)->f_lck, "ftlk", NULL, \ 172 MTX_DUPOK); \ 173 LIN_SDT_PROBE1(futex, futex, create, \ 174 &(f)->f_lck); \ 175 } while (0) 176 #define FUTEX_DESTROY(f) do { \ 177 LIN_SDT_PROBE1(futex, futex, destroy, \ 178 &(f)->f_lck); \ 179 mtx_destroy(&(f)->f_lck); \ 180 } while (0) 181 #define FUTEX_ASSERT_LOCKED(f) mtx_assert(&(f)->f_lck, MA_OWNED) 182 #define FUTEX_ASSERT_UNLOCKED(f) mtx_assert(&(f)->f_lck, MA_NOTOWNED) 183 184 #define FUTEXES_LOCK do { \ 185 mtx_lock(&futex_mtx); \ 186 LIN_SDT_PROBE1(locks, futex_mtx, \ 187 locked, &futex_mtx); \ 188 } while (0) 189 #define FUTEXES_UNLOCK do { \ 190 LIN_SDT_PROBE1(locks, futex_mtx, \ 191 unlock, &futex_mtx); \ 192 mtx_unlock(&futex_mtx); \ 193 } while (0) 194 195 /* flags for futex_get() */ 196 #define FUTEX_CREATE_WP 0x1 /* create waiting_proc */ 197 #define FUTEX_DONTCREATE 0x2 /* don't create futex if not exists */ 198 #define FUTEX_DONTEXISTS 0x4 /* return EINVAL if futex exists */ 199 #define FUTEX_SHARED 0x8 /* shared futex */ 200 #define FUTEX_DONTLOCK 0x10 /* don't lock futex */ 201 202 /* wp_flags */ 203 #define FUTEX_WP_REQUEUED 0x1 /* wp requeued - wp moved from wp_list 204 * of futex where thread sleep to wp_list 205 * of another futex. 206 */ 207 #define FUTEX_WP_REMOVED 0x2 /* wp is woken up and removed from futex 208 * wp_list to prevent double wakeup. 209 */ 210 211 static void futex_put(struct futex *, struct waiting_proc *); 212 static int futex_get0(uint32_t *, struct futex **f, uint32_t); 213 static int futex_get(uint32_t *, struct waiting_proc **, struct futex **, 214 uint32_t); 215 static int futex_sleep(struct futex *, struct waiting_proc *, struct timespec *); 216 static int futex_wake(struct futex *, int, uint32_t); 217 static int futex_requeue(struct futex *, int, struct futex *, int); 218 static int futex_wait(struct futex *, struct waiting_proc *, struct timespec *, 219 uint32_t); 220 static void futex_lock(struct futex *); 221 static void futex_unlock(struct futex *); 222 static int futex_atomic_op(struct thread *, int, uint32_t *); 223 static int handle_futex_death(struct linux_emuldata *, uint32_t *, 224 unsigned int); 225 static int fetch_robust_entry(struct linux_robust_list **, 226 struct linux_robust_list **, unsigned int *); 227 228 struct linux_futex_args { 229 uint32_t *uaddr; 230 int32_t op; 231 uint32_t val; 232 struct timespec *ts; 233 uint32_t *uaddr2; 234 uint32_t val3; 235 struct timespec kts; 236 }; 237 238 static int linux_futex(struct thread *, struct linux_futex_args *); 239 240 static void 241 futex_put(struct futex *f, struct waiting_proc *wp) 242 { 243 244 if (wp != NULL) { 245 if ((wp->wp_flags & FUTEX_WP_REMOVED) == 0) 246 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list); 247 free(wp, M_FUTEX_WP); 248 } 249 250 FUTEXES_LOCK; 251 if (--f->f_refcount == 0) { 252 LIST_REMOVE(f, f_list); 253 FUTEXES_UNLOCK; 254 if (FUTEX_LOCKED(f)) 255 futex_unlock(f); 256 257 LIN_SDT_PROBE3(futex, futex_put, destroy, f->f_uaddr, 258 f->f_refcount, f->f_key.shared); 259 LINUX_CTR3(sys_futex, "futex_put destroy uaddr %p ref %d " 260 "shared %d", f->f_uaddr, f->f_refcount, f->f_key.shared); 261 umtx_key_release(&f->f_key); 262 FUTEX_DESTROY(f); 263 free(f, M_FUTEX); 264 return; 265 } 266 267 LIN_SDT_PROBE3(futex, futex_put, unlock, f->f_uaddr, f->f_refcount, 268 f->f_key.shared); 269 LINUX_CTR3(sys_futex, "futex_put uaddr %p ref %d shared %d", 270 f->f_uaddr, f->f_refcount, f->f_key.shared); 271 if (FUTEX_LOCKED(f)) 272 futex_unlock(f); 273 FUTEXES_UNLOCK; 274 } 275 276 static int 277 futex_get0(uint32_t *uaddr, struct futex **newf, uint32_t flags) 278 { 279 struct futex *f, *tmpf; 280 struct umtx_key key; 281 int error; 282 283 *newf = tmpf = NULL; 284 285 error = umtx_key_get(uaddr, TYPE_FUTEX, (flags & FUTEX_SHARED) ? 286 AUTO_SHARE : THREAD_SHARE, &key); 287 if (error) { 288 LIN_SDT_PROBE1(futex, futex_get0, umtx_key_get_error, error); 289 return (error); 290 } 291 retry: 292 FUTEXES_LOCK; 293 LIST_FOREACH(f, &futex_list, f_list) { 294 if (umtx_key_match(&f->f_key, &key)) { 295 if (tmpf != NULL) { 296 if (FUTEX_LOCKED(tmpf)) 297 futex_unlock(tmpf); 298 FUTEX_DESTROY(tmpf); 299 free(tmpf, M_FUTEX); 300 } 301 if (flags & FUTEX_DONTEXISTS) { 302 FUTEXES_UNLOCK; 303 umtx_key_release(&key); 304 305 return (EINVAL); 306 } 307 308 /* 309 * Increment refcount of the found futex to 310 * prevent it from deallocation before FUTEX_LOCK() 311 */ 312 ++f->f_refcount; 313 FUTEXES_UNLOCK; 314 umtx_key_release(&key); 315 316 if ((flags & FUTEX_DONTLOCK) == 0) 317 futex_lock(f); 318 *newf = f; 319 LIN_SDT_PROBE3(futex, futex_get0, shared, uaddr, 320 f->f_refcount, f->f_key.shared); 321 LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d", 322 uaddr, f->f_refcount, f->f_key.shared); 323 324 return (0); 325 } 326 } 327 328 if (flags & FUTEX_DONTCREATE) { 329 FUTEXES_UNLOCK; 330 umtx_key_release(&key); 331 LIN_SDT_PROBE1(futex, futex_get0, null, uaddr); 332 LINUX_CTR1(sys_futex, "futex_get uaddr %p null", uaddr); 333 334 return (0); 335 } 336 337 if (tmpf == NULL) { 338 FUTEXES_UNLOCK; 339 tmpf = malloc(sizeof(*tmpf), M_FUTEX, M_WAITOK | M_ZERO); 340 tmpf->f_uaddr = uaddr; 341 tmpf->f_key = key; 342 tmpf->f_refcount = 1; 343 tmpf->f_bitset = FUTEX_BITSET_MATCH_ANY; 344 FUTEX_INIT(tmpf); 345 TAILQ_INIT(&tmpf->f_waiting_proc); 346 347 /* 348 * Lock the new futex before an insert into the futex_list 349 * to prevent futex usage by other. 350 */ 351 if ((flags & FUTEX_DONTLOCK) == 0) 352 futex_lock(tmpf); 353 goto retry; 354 } 355 356 LIST_INSERT_HEAD(&futex_list, tmpf, f_list); 357 FUTEXES_UNLOCK; 358 359 LIN_SDT_PROBE3(futex, futex_get0, new, uaddr, tmpf->f_refcount, 360 tmpf->f_key.shared); 361 LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d new", 362 uaddr, tmpf->f_refcount, tmpf->f_key.shared); 363 *newf = tmpf; 364 365 return (0); 366 } 367 368 static int 369 futex_get(uint32_t *uaddr, struct waiting_proc **wp, struct futex **f, 370 uint32_t flags) 371 { 372 int error; 373 374 if (flags & FUTEX_CREATE_WP) { 375 *wp = malloc(sizeof(struct waiting_proc), M_FUTEX_WP, M_WAITOK); 376 (*wp)->wp_flags = 0; 377 } 378 error = futex_get0(uaddr, f, flags); 379 if (error) { 380 LIN_SDT_PROBE0(futex, futex_get, error); 381 382 if (flags & FUTEX_CREATE_WP) 383 free(*wp, M_FUTEX_WP); 384 385 return (error); 386 } 387 if (flags & FUTEX_CREATE_WP) { 388 TAILQ_INSERT_HEAD(&(*f)->f_waiting_proc, *wp, wp_list); 389 (*wp)->wp_futex = *f; 390 } 391 392 return (error); 393 } 394 395 static inline void 396 futex_lock(struct futex *f) 397 { 398 399 LINUX_CTR3(sys_futex, "futex_lock uaddr %p ref %d shared %d", 400 f->f_uaddr, f->f_refcount, f->f_key.shared); 401 FUTEX_ASSERT_UNLOCKED(f); 402 FUTEX_LOCK(f); 403 } 404 405 static inline void 406 futex_unlock(struct futex *f) 407 { 408 409 LINUX_CTR3(sys_futex, "futex_unlock uaddr %p ref %d shared %d", 410 f->f_uaddr, f->f_refcount, f->f_key.shared); 411 FUTEX_ASSERT_LOCKED(f); 412 FUTEX_UNLOCK(f); 413 } 414 415 static int 416 futex_sleep(struct futex *f, struct waiting_proc *wp, struct timespec *ts) 417 { 418 sbintime_t sbt, prec, tmp; 419 time_t over; 420 int error; 421 422 FUTEX_ASSERT_LOCKED(f); 423 if (ts != NULL) { 424 if (ts->tv_sec > INT32_MAX / 2) { 425 over = ts->tv_sec - INT32_MAX / 2; 426 ts->tv_sec -= over; 427 } 428 tmp = tstosbt(*ts); 429 if (TIMESEL(&sbt, tmp)) 430 sbt += tc_tick_sbt; 431 sbt += tmp; 432 prec = tmp; 433 prec >>= tc_precexp; 434 } else { 435 sbt = 0; 436 prec = 0; 437 } 438 LINUX_CTR4(sys_futex, "futex_sleep enter uaddr %p wp %p timo %ld ref %d", 439 f->f_uaddr, wp, sbt, f->f_refcount); 440 441 error = msleep_sbt(wp, &f->f_lck, PCATCH, "futex", sbt, prec, C_ABSOLUTE); 442 if (wp->wp_flags & FUTEX_WP_REQUEUED) { 443 KASSERT(f != wp->wp_futex, ("futex != wp_futex")); 444 445 if (error) { 446 LIN_SDT_PROBE5(futex, futex_sleep, requeue_error, error, 447 f->f_uaddr, wp, wp->wp_futex->f_uaddr, 448 wp->wp_futex->f_refcount); 449 } 450 451 LINUX_CTR5(sys_futex, "futex_sleep out error %d uaddr %p wp" 452 " %p requeued uaddr %p ref %d", 453 error, f->f_uaddr, wp, wp->wp_futex->f_uaddr, 454 wp->wp_futex->f_refcount); 455 futex_put(f, NULL); 456 f = wp->wp_futex; 457 futex_lock(f); 458 } else { 459 if (error) { 460 LIN_SDT_PROBE3(futex, futex_sleep, sleep_error, error, 461 f->f_uaddr, wp); 462 } 463 LINUX_CTR3(sys_futex, "futex_sleep out error %d uaddr %p wp %p", 464 error, f->f_uaddr, wp); 465 } 466 467 futex_put(f, wp); 468 469 return (error); 470 } 471 472 static int 473 futex_wake(struct futex *f, int n, uint32_t bitset) 474 { 475 struct waiting_proc *wp, *wpt; 476 int count = 0; 477 478 if (bitset == 0) 479 return (EINVAL); 480 481 FUTEX_ASSERT_LOCKED(f); 482 TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) { 483 LIN_SDT_PROBE3(futex, futex_wake, iterate, f->f_uaddr, wp, 484 f->f_refcount); 485 LINUX_CTR3(sys_futex, "futex_wake uaddr %p wp %p ref %d", 486 f->f_uaddr, wp, f->f_refcount); 487 /* 488 * Unless we find a matching bit in 489 * the bitset, continue searching. 490 */ 491 if (!(wp->wp_futex->f_bitset & bitset)) 492 continue; 493 494 wp->wp_flags |= FUTEX_WP_REMOVED; 495 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list); 496 LIN_SDT_PROBE1(futex, futex_wake, wakeup, wp); 497 wakeup_one(wp); 498 if (++count == n) 499 break; 500 } 501 502 return (count); 503 } 504 505 static int 506 futex_requeue(struct futex *f, int nrwake, struct futex *f2, 507 int nrrequeue) 508 { 509 struct waiting_proc *wp, *wpt; 510 int count = 0; 511 512 FUTEX_ASSERT_LOCKED(f); 513 FUTEX_ASSERT_LOCKED(f2); 514 515 TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) { 516 if (++count <= nrwake) { 517 LINUX_CTR2(sys_futex, "futex_req_wake uaddr %p wp %p", 518 f->f_uaddr, wp); 519 wp->wp_flags |= FUTEX_WP_REMOVED; 520 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list); 521 LIN_SDT_PROBE1(futex, futex_requeue, wakeup, wp); 522 wakeup_one(wp); 523 } else { 524 LIN_SDT_PROBE3(futex, futex_requeue, requeue, 525 f->f_uaddr, wp, f2->f_uaddr); 526 LINUX_CTR3(sys_futex, "futex_requeue uaddr %p wp %p to %p", 527 f->f_uaddr, wp, f2->f_uaddr); 528 wp->wp_flags |= FUTEX_WP_REQUEUED; 529 /* Move wp to wp_list of f2 futex */ 530 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list); 531 TAILQ_INSERT_HEAD(&f2->f_waiting_proc, wp, wp_list); 532 533 /* 534 * Thread which sleeps on wp after waking should 535 * acquire f2 lock, so increment refcount of f2 to 536 * prevent it from premature deallocation. 537 */ 538 wp->wp_futex = f2; 539 FUTEXES_LOCK; 540 ++f2->f_refcount; 541 FUTEXES_UNLOCK; 542 if (count - nrwake >= nrrequeue) 543 break; 544 } 545 } 546 547 return (count); 548 } 549 550 static int 551 futex_wait(struct futex *f, struct waiting_proc *wp, struct timespec *ts, 552 uint32_t bitset) 553 { 554 int error; 555 556 if (bitset == 0) { 557 futex_put(f, wp); 558 return (EINVAL); 559 } 560 561 f->f_bitset = bitset; 562 error = futex_sleep(f, wp, ts); 563 if (error) 564 LIN_SDT_PROBE1(futex, futex_wait, sleep_error, error); 565 if (error == EWOULDBLOCK) 566 error = ETIMEDOUT; 567 568 return (error); 569 } 570 571 static int 572 futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr) 573 { 574 int op = (encoded_op >> 28) & 7; 575 int cmp = (encoded_op >> 24) & 15; 576 int oparg = (encoded_op << 8) >> 20; 577 int cmparg = (encoded_op << 20) >> 20; 578 int oldval = 0, ret; 579 580 if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) 581 oparg = 1 << oparg; 582 583 LIN_SDT_PROBE4(futex, futex_atomic_op, decoded_op, op, cmp, oparg, 584 cmparg); 585 586 /* XXX: Linux verifies access here and returns EFAULT */ 587 LIN_SDT_PROBE0(futex, futex_atomic_op, missing_access_check); 588 589 switch (op) { 590 case FUTEX_OP_SET: 591 ret = futex_xchgl(oparg, uaddr, &oldval); 592 break; 593 case FUTEX_OP_ADD: 594 ret = futex_addl(oparg, uaddr, &oldval); 595 break; 596 case FUTEX_OP_OR: 597 ret = futex_orl(oparg, uaddr, &oldval); 598 break; 599 case FUTEX_OP_ANDN: 600 ret = futex_andl(~oparg, uaddr, &oldval); 601 break; 602 case FUTEX_OP_XOR: 603 ret = futex_xorl(oparg, uaddr, &oldval); 604 break; 605 default: 606 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_op, op); 607 ret = -ENOSYS; 608 break; 609 } 610 611 if (ret) 612 return (ret); 613 614 switch (cmp) { 615 case FUTEX_OP_CMP_EQ: 616 ret = (oldval == cmparg); 617 break; 618 case FUTEX_OP_CMP_NE: 619 ret = (oldval != cmparg); 620 break; 621 case FUTEX_OP_CMP_LT: 622 ret = (oldval < cmparg); 623 break; 624 case FUTEX_OP_CMP_GE: 625 ret = (oldval >= cmparg); 626 break; 627 case FUTEX_OP_CMP_LE: 628 ret = (oldval <= cmparg); 629 break; 630 case FUTEX_OP_CMP_GT: 631 ret = (oldval > cmparg); 632 break; 633 default: 634 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_cmp, cmp); 635 ret = -ENOSYS; 636 } 637 638 return (ret); 639 } 640 641 static int 642 linux_futex(struct thread *td, struct linux_futex_args *args) 643 { 644 int clockrt, nrwake, nrrequeue, op_ret, ret; 645 struct linux_pemuldata *pem; 646 struct waiting_proc *wp; 647 struct futex *f, *f2; 648 struct timespec kts; 649 int error, save; 650 uint32_t flags, val; 651 652 if (args->op & LINUX_FUTEX_PRIVATE_FLAG) { 653 flags = 0; 654 args->op &= ~LINUX_FUTEX_PRIVATE_FLAG; 655 } else 656 flags = FUTEX_SHARED; 657 658 /* 659 * Currently support for switching between CLOCK_MONOTONIC and 660 * CLOCK_REALTIME is not present. However Linux forbids the use of 661 * FUTEX_CLOCK_REALTIME with any op except FUTEX_WAIT_BITSET and 662 * FUTEX_WAIT_REQUEUE_PI. 663 */ 664 clockrt = args->op & LINUX_FUTEX_CLOCK_REALTIME; 665 args->op = args->op & ~LINUX_FUTEX_CLOCK_REALTIME; 666 if (clockrt && args->op != LINUX_FUTEX_WAIT_BITSET && 667 args->op != LINUX_FUTEX_WAIT_REQUEUE_PI) { 668 LIN_SDT_PROBE0(futex, linux_futex, 669 unimplemented_clockswitch); 670 return (ENOSYS); 671 } 672 673 error = 0; 674 f = f2 = NULL; 675 676 switch (args->op) { 677 case LINUX_FUTEX_WAIT: 678 args->val3 = FUTEX_BITSET_MATCH_ANY; 679 /* FALLTHROUGH */ 680 681 case LINUX_FUTEX_WAIT_BITSET: 682 LIN_SDT_PROBE3(futex, linux_futex, debug_wait, args->uaddr, 683 args->val, args->val3); 684 LINUX_CTR3(sys_futex, "WAIT uaddr %p val 0x%x bitset 0x%x", 685 args->uaddr, args->val, args->val3); 686 687 if (args->ts != NULL) { 688 if (clockrt) { 689 nanotime(&kts); 690 timespecsub(args->ts, &kts, args->ts); 691 } else if (args->op == LINUX_FUTEX_WAIT_BITSET) { 692 nanouptime(&kts); 693 timespecsub(args->ts, &kts, args->ts); 694 } 695 } 696 697 retry0: 698 error = futex_get(args->uaddr, &wp, &f, 699 flags | FUTEX_CREATE_WP); 700 if (error) 701 return (error); 702 703 error = copyin_nofault(args->uaddr, &val, sizeof(val)); 704 if (error) { 705 futex_put(f, wp); 706 error = copyin(args->uaddr, &val, sizeof(val)); 707 if (error == 0) 708 goto retry0; 709 LIN_SDT_PROBE1(futex, linux_futex, copyin_error, 710 error); 711 LINUX_CTR1(sys_futex, "WAIT copyin failed %d", 712 error); 713 return (error); 714 } 715 if (val != args->val) { 716 LIN_SDT_PROBE4(futex, linux_futex, 717 debug_wait_value_neq, args->uaddr, args->val, val, 718 args->val3); 719 LINUX_CTR3(sys_futex, 720 "WAIT uaddr %p val 0x%x != uval 0x%x", 721 args->uaddr, args->val, val); 722 futex_put(f, wp); 723 return (EWOULDBLOCK); 724 } 725 726 error = futex_wait(f, wp, args->ts, args->val3); 727 break; 728 729 case LINUX_FUTEX_WAKE: 730 args->val3 = FUTEX_BITSET_MATCH_ANY; 731 /* FALLTHROUGH */ 732 733 case LINUX_FUTEX_WAKE_BITSET: 734 LIN_SDT_PROBE3(futex, linux_futex, debug_wake, args->uaddr, 735 args->val, args->val3); 736 LINUX_CTR3(sys_futex, "WAKE uaddr %p nrwake 0x%x bitset 0x%x", 737 args->uaddr, args->val, args->val3); 738 739 error = futex_get(args->uaddr, NULL, &f, 740 flags | FUTEX_DONTCREATE); 741 if (error) 742 return (error); 743 744 if (f == NULL) { 745 td->td_retval[0] = 0; 746 return (error); 747 } 748 td->td_retval[0] = futex_wake(f, args->val, args->val3); 749 futex_put(f, NULL); 750 break; 751 752 case LINUX_FUTEX_CMP_REQUEUE: 753 LIN_SDT_PROBE5(futex, linux_futex, debug_cmp_requeue, 754 args->uaddr, args->val, args->val3, args->uaddr2, 755 args->ts); 756 LINUX_CTR5(sys_futex, "CMP_REQUEUE uaddr %p " 757 "nrwake 0x%x uval 0x%x uaddr2 %p nrequeue 0x%x", 758 args->uaddr, args->val, args->val3, args->uaddr2, 759 args->ts); 760 761 /* 762 * Linux allows this, we would not, it is an incorrect 763 * usage of declared ABI, so return EINVAL. 764 */ 765 if (args->uaddr == args->uaddr2) { 766 LIN_SDT_PROBE0(futex, linux_futex, 767 invalid_cmp_requeue_use); 768 return (EINVAL); 769 } 770 771 nrrequeue = (int)(unsigned long)args->ts; 772 nrwake = args->val; 773 /* 774 * Sanity check to prevent signed integer overflow, 775 * see Linux CVE-2018-6927 776 */ 777 if (nrwake < 0 || nrrequeue < 0) 778 return (EINVAL); 779 780 retry1: 781 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK); 782 if (error) 783 return (error); 784 785 /* 786 * To avoid deadlocks return EINVAL if second futex 787 * exists at this time. 788 * 789 * Glibc fall back to FUTEX_WAKE in case of any error 790 * returned by FUTEX_CMP_REQUEUE. 791 */ 792 error = futex_get(args->uaddr2, NULL, &f2, 793 flags | FUTEX_DONTEXISTS | FUTEX_DONTLOCK); 794 if (error) { 795 futex_put(f, NULL); 796 return (error); 797 } 798 futex_lock(f); 799 futex_lock(f2); 800 error = copyin_nofault(args->uaddr, &val, sizeof(val)); 801 if (error) { 802 futex_put(f2, NULL); 803 futex_put(f, NULL); 804 error = copyin(args->uaddr, &val, sizeof(val)); 805 if (error == 0) 806 goto retry1; 807 LIN_SDT_PROBE1(futex, linux_futex, copyin_error, 808 error); 809 LINUX_CTR1(sys_futex, "CMP_REQUEUE copyin failed %d", 810 error); 811 return (error); 812 } 813 if (val != args->val3) { 814 LIN_SDT_PROBE2(futex, linux_futex, 815 debug_cmp_requeue_value_neq, args->val, val); 816 LINUX_CTR2(sys_futex, "CMP_REQUEUE val 0x%x != uval 0x%x", 817 args->val, val); 818 futex_put(f2, NULL); 819 futex_put(f, NULL); 820 return (EAGAIN); 821 } 822 823 td->td_retval[0] = futex_requeue(f, nrwake, f2, nrrequeue); 824 futex_put(f2, NULL); 825 futex_put(f, NULL); 826 break; 827 828 case LINUX_FUTEX_WAKE_OP: 829 LIN_SDT_PROBE5(futex, linux_futex, debug_wake_op, 830 args->uaddr, args->op, args->val, args->uaddr2, args->val3); 831 LINUX_CTR5(sys_futex, "WAKE_OP " 832 "uaddr %p nrwake 0x%x uaddr2 %p op 0x%x nrwake2 0x%x", 833 args->uaddr, args->val, args->uaddr2, args->val3, 834 args->ts); 835 836 if (args->uaddr == args->uaddr2) 837 return (EINVAL); 838 839 retry2: 840 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK); 841 if (error) 842 return (error); 843 844 error = futex_get(args->uaddr2, NULL, &f2, flags | FUTEX_DONTLOCK); 845 if (error) { 846 futex_put(f, NULL); 847 return (error); 848 } 849 futex_lock(f); 850 futex_lock(f2); 851 852 /* 853 * This function returns positive number as results and 854 * negative as errors 855 */ 856 save = vm_fault_disable_pagefaults(); 857 op_ret = futex_atomic_op(td, args->val3, args->uaddr2); 858 vm_fault_enable_pagefaults(save); 859 860 LINUX_CTR2(sys_futex, "WAKE_OP atomic_op uaddr %p ret 0x%x", 861 args->uaddr, op_ret); 862 863 if (op_ret < 0) { 864 if (f2 != NULL) 865 futex_put(f2, NULL); 866 futex_put(f, NULL); 867 error = copyin(args->uaddr2, &val, sizeof(val)); 868 if (error == 0) 869 goto retry2; 870 return (error); 871 } 872 873 ret = futex_wake(f, args->val, args->val3); 874 875 if (op_ret > 0) { 876 op_ret = 0; 877 nrwake = (int)(unsigned long)args->ts; 878 879 if (f2 != NULL) 880 op_ret += futex_wake(f2, nrwake, args->val3); 881 else 882 op_ret += futex_wake(f, nrwake, args->val3); 883 ret += op_ret; 884 } 885 if (f2 != NULL) 886 futex_put(f2, NULL); 887 futex_put(f, NULL); 888 td->td_retval[0] = ret; 889 break; 890 891 case LINUX_FUTEX_LOCK_PI: 892 /* not yet implemented */ 893 pem = pem_find(td->td_proc); 894 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) { 895 linux_msg(td, "unsupported FUTEX_LOCK_PI"); 896 pem->flags |= LINUX_XUNSUP_FUTEXPIOP; 897 LIN_SDT_PROBE0(futex, linux_futex, 898 unimplemented_lock_pi); 899 } 900 return (ENOSYS); 901 902 case LINUX_FUTEX_UNLOCK_PI: 903 /* not yet implemented */ 904 pem = pem_find(td->td_proc); 905 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) { 906 linux_msg(td, "unsupported FUTEX_UNLOCK_PI"); 907 pem->flags |= LINUX_XUNSUP_FUTEXPIOP; 908 LIN_SDT_PROBE0(futex, linux_futex, 909 unimplemented_unlock_pi); 910 } 911 return (ENOSYS); 912 913 case LINUX_FUTEX_TRYLOCK_PI: 914 /* not yet implemented */ 915 pem = pem_find(td->td_proc); 916 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) { 917 linux_msg(td, "unsupported FUTEX_TRYLOCK_PI"); 918 pem->flags |= LINUX_XUNSUP_FUTEXPIOP; 919 LIN_SDT_PROBE0(futex, linux_futex, 920 unimplemented_trylock_pi); 921 } 922 return (ENOSYS); 923 924 case LINUX_FUTEX_REQUEUE: 925 /* 926 * Glibc does not use this operation since version 2.3.3, 927 * as it is racy and replaced by FUTEX_CMP_REQUEUE operation. 928 * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when 929 * FUTEX_REQUEUE returned EINVAL. 930 */ 931 pem = pem_find(td->td_proc); 932 if ((pem->flags & LINUX_XDEPR_REQUEUEOP) == 0) { 933 linux_msg(td, "unsupported FUTEX_REQUEUE"); 934 pem->flags |= LINUX_XDEPR_REQUEUEOP; 935 LIN_SDT_PROBE0(futex, linux_futex, 936 deprecated_requeue); 937 } 938 return (EINVAL); 939 940 case LINUX_FUTEX_WAIT_REQUEUE_PI: 941 /* not yet implemented */ 942 pem = pem_find(td->td_proc); 943 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) { 944 linux_msg(td, "unsupported FUTEX_WAIT_REQUEUE_PI"); 945 pem->flags |= LINUX_XUNSUP_FUTEXPIOP; 946 LIN_SDT_PROBE0(futex, linux_futex, 947 unimplemented_wait_requeue_pi); 948 } 949 return (ENOSYS); 950 951 case LINUX_FUTEX_CMP_REQUEUE_PI: 952 /* not yet implemented */ 953 pem = pem_find(td->td_proc); 954 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) { 955 linux_msg(td, "unsupported FUTEX_CMP_REQUEUE_PI"); 956 pem->flags |= LINUX_XUNSUP_FUTEXPIOP; 957 LIN_SDT_PROBE0(futex, linux_futex, 958 unimplemented_cmp_requeue_pi); 959 } 960 return (ENOSYS); 961 962 default: 963 linux_msg(td, "unsupported futex op %d", args->op); 964 LIN_SDT_PROBE1(futex, linux_futex, unknown_operation, 965 args->op); 966 return (ENOSYS); 967 } 968 969 return (error); 970 } 971 972 int 973 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args) 974 { 975 struct linux_futex_args fargs = { 976 .uaddr = args->uaddr, 977 .op = args->op, 978 .val = args->val, 979 .ts = NULL, 980 .uaddr2 = args->uaddr2, 981 .val3 = args->val3, 982 }; 983 struct l_timespec lts; 984 int error; 985 986 switch (args->op & LINUX_FUTEX_CMD_MASK) { 987 case LINUX_FUTEX_WAIT: 988 case LINUX_FUTEX_WAIT_BITSET: 989 if (args->timeout != NULL) { 990 error = copyin(args->timeout, <s, sizeof(lts)); 991 if (error != 0) 992 return (error); 993 error = linux_to_native_timespec(&fargs.kts, <s); 994 if (error != 0) 995 return (error); 996 fargs.ts = &fargs.kts; 997 } 998 break; 999 default: 1000 fargs.ts = PTRIN(args->timeout); 1001 } 1002 return (linux_futex(td, &fargs)); 1003 } 1004 1005 #if defined(__i386__) || (defined(__amd64__) && defined(COMPAT_LINUX32)) 1006 int 1007 linux_sys_futex_time64(struct thread *td, 1008 struct linux_sys_futex_time64_args *args) 1009 { 1010 struct linux_futex_args fargs = { 1011 .uaddr = args->uaddr, 1012 .op = args->op, 1013 .val = args->val, 1014 .ts = NULL, 1015 .uaddr2 = args->uaddr2, 1016 .val3 = args->val3, 1017 }; 1018 struct l_timespec64 lts; 1019 int error; 1020 1021 switch (args->op & LINUX_FUTEX_CMD_MASK) { 1022 case LINUX_FUTEX_WAIT: 1023 case LINUX_FUTEX_WAIT_BITSET: 1024 if (args->timeout != NULL) { 1025 error = copyin(args->timeout, <s, sizeof(lts)); 1026 if (error != 0) 1027 return (error); 1028 error = linux_to_native_timespec64(&fargs.kts, <s); 1029 if (error != 0) 1030 return (error); 1031 fargs.ts = &fargs.kts; 1032 } 1033 break; 1034 default: 1035 fargs.ts = PTRIN(args->timeout); 1036 } 1037 return (linux_futex(td, &fargs)); 1038 } 1039 #endif 1040 1041 int 1042 linux_set_robust_list(struct thread *td, struct linux_set_robust_list_args *args) 1043 { 1044 struct linux_emuldata *em; 1045 1046 if (args->len != sizeof(struct linux_robust_list_head)) { 1047 LIN_SDT_PROBE0(futex, linux_set_robust_list, size_error); 1048 return (EINVAL); 1049 } 1050 1051 em = em_find(td); 1052 em->robust_futexes = args->head; 1053 1054 return (0); 1055 } 1056 1057 int 1058 linux_get_robust_list(struct thread *td, struct linux_get_robust_list_args *args) 1059 { 1060 struct linux_emuldata *em; 1061 struct linux_robust_list_head *head; 1062 l_size_t len = sizeof(struct linux_robust_list_head); 1063 struct thread *td2; 1064 int error = 0; 1065 1066 if (!args->pid) { 1067 em = em_find(td); 1068 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n")); 1069 head = em->robust_futexes; 1070 } else { 1071 td2 = tdfind(args->pid, -1); 1072 if (td2 == NULL) 1073 return (ESRCH); 1074 if (SV_PROC_ABI(td2->td_proc) != SV_ABI_LINUX) { 1075 PROC_UNLOCK(td2->td_proc); 1076 return (EPERM); 1077 } 1078 1079 em = em_find(td2); 1080 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n")); 1081 /* XXX: ptrace? */ 1082 if (priv_check(td, PRIV_CRED_SETUID) || 1083 priv_check(td, PRIV_CRED_SETEUID) || 1084 p_candebug(td, td2->td_proc)) { 1085 PROC_UNLOCK(td2->td_proc); 1086 return (EPERM); 1087 } 1088 head = em->robust_futexes; 1089 1090 PROC_UNLOCK(td2->td_proc); 1091 } 1092 1093 error = copyout(&len, args->len, sizeof(l_size_t)); 1094 if (error) { 1095 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error, 1096 error); 1097 return (EFAULT); 1098 } 1099 1100 error = copyout(&head, args->head, sizeof(head)); 1101 if (error) { 1102 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error, 1103 error); 1104 } 1105 1106 return (error); 1107 } 1108 1109 static int 1110 handle_futex_death(struct linux_emuldata *em, uint32_t *uaddr, 1111 unsigned int pi) 1112 { 1113 uint32_t uval, nval, mval; 1114 struct futex *f; 1115 int error; 1116 1117 retry: 1118 error = copyin(uaddr, &uval, 4); 1119 if (error) { 1120 LIN_SDT_PROBE1(futex, handle_futex_death, copyin_error, error); 1121 return (EFAULT); 1122 } 1123 if ((uval & FUTEX_TID_MASK) == em->em_tid) { 1124 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; 1125 nval = casuword32(uaddr, uval, mval); 1126 1127 if (nval == -1) 1128 return (EFAULT); 1129 1130 if (nval != uval) 1131 goto retry; 1132 1133 if (!pi && (uval & FUTEX_WAITERS)) { 1134 error = futex_get(uaddr, NULL, &f, 1135 FUTEX_DONTCREATE | FUTEX_SHARED); 1136 if (error) 1137 return (error); 1138 if (f != NULL) { 1139 futex_wake(f, 1, FUTEX_BITSET_MATCH_ANY); 1140 futex_put(f, NULL); 1141 } 1142 } 1143 } 1144 1145 return (0); 1146 } 1147 1148 static int 1149 fetch_robust_entry(struct linux_robust_list **entry, 1150 struct linux_robust_list **head, unsigned int *pi) 1151 { 1152 l_ulong uentry; 1153 int error; 1154 1155 error = copyin((const void *)head, &uentry, sizeof(l_ulong)); 1156 if (error) { 1157 LIN_SDT_PROBE1(futex, fetch_robust_entry, copyin_error, error); 1158 return (EFAULT); 1159 } 1160 1161 *entry = (void *)(uentry & ~1UL); 1162 *pi = uentry & 1; 1163 1164 return (0); 1165 } 1166 1167 /* This walks the list of robust futexes releasing them. */ 1168 void 1169 release_futexes(struct thread *td, struct linux_emuldata *em) 1170 { 1171 struct linux_robust_list_head *head = NULL; 1172 struct linux_robust_list *entry, *next_entry, *pending; 1173 unsigned int limit = 2048, pi, next_pi, pip; 1174 l_long futex_offset; 1175 int rc, error; 1176 1177 head = em->robust_futexes; 1178 1179 if (head == NULL) 1180 return; 1181 1182 if (fetch_robust_entry(&entry, PTRIN(&head->list.next), &pi)) 1183 return; 1184 1185 error = copyin(&head->futex_offset, &futex_offset, 1186 sizeof(futex_offset)); 1187 if (error) { 1188 LIN_SDT_PROBE1(futex, release_futexes, copyin_error, error); 1189 return; 1190 } 1191 1192 if (fetch_robust_entry(&pending, PTRIN(&head->pending_list), &pip)) 1193 return; 1194 1195 while (entry != &head->list) { 1196 rc = fetch_robust_entry(&next_entry, PTRIN(&entry->next), &next_pi); 1197 1198 if (entry != pending) 1199 if (handle_futex_death(em, 1200 (uint32_t *)((caddr_t)entry + futex_offset), pi)) { 1201 return; 1202 } 1203 if (rc) 1204 return; 1205 1206 entry = next_entry; 1207 pi = next_pi; 1208 1209 if (!--limit) 1210 break; 1211 1212 sched_relinquish(curthread); 1213 } 1214 1215 if (pending) 1216 handle_futex_death(em, (uint32_t *)((caddr_t)pending + futex_offset), pip); 1217 } 1218