1 /* $NetBSD: sys_select.c,v 1.48 2019/09/20 15:00:47 kamil Exp $ */ 2 3 /*- 4 * Copyright (c) 2007, 2008, 2009, 2010 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 and Mindaugas Rasiukevicius. 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 * Copyright (c) 1982, 1986, 1989, 1993 34 * The Regents of the University of California. All rights reserved. 35 * (c) UNIX System Laboratories, Inc. 36 * All or some portions of this file are derived from material licensed 37 * to the University of California by American Telephone and Telegraph 38 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 39 * the permission of UNIX System Laboratories, Inc. 40 * 41 * Redistribution and use in source and binary forms, with or without 42 * modification, are permitted provided that the following conditions 43 * are met: 44 * 1. Redistributions of source code must retain the above copyright 45 * notice, this list of conditions and the following disclaimer. 46 * 2. Redistributions in binary form must reproduce the above copyright 47 * notice, this list of conditions and the following disclaimer in the 48 * documentation and/or other materials provided with the distribution. 49 * 3. Neither the name of the University nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 63 * SUCH DAMAGE. 64 * 65 * @(#)sys_generic.c 8.9 (Berkeley) 2/14/95 66 */ 67 68 /* 69 * System calls of synchronous I/O multiplexing subsystem. 70 * 71 * Locking 72 * 73 * Two locks are used: <object-lock> and selcluster_t::sc_lock. 74 * 75 * The <object-lock> might be a device driver or another subsystem, e.g. 76 * socket or pipe. This lock is not exported, and thus invisible to this 77 * subsystem. Mainly, synchronisation between selrecord() and selnotify() 78 * routines depends on this lock, as it will be described in the comments. 79 * 80 * Lock order 81 * 82 * <object-lock> -> 83 * selcluster_t::sc_lock 84 */ 85 86 #include <sys/cdefs.h> 87 __KERNEL_RCSID(0, "$NetBSD: sys_select.c,v 1.48 2019/09/20 15:00:47 kamil Exp $"); 88 89 #include <sys/param.h> 90 #include <sys/systm.h> 91 #include <sys/filedesc.h> 92 #include <sys/file.h> 93 #include <sys/proc.h> 94 #include <sys/socketvar.h> 95 #include <sys/signalvar.h> 96 #include <sys/uio.h> 97 #include <sys/kernel.h> 98 #include <sys/lwp.h> 99 #include <sys/poll.h> 100 #include <sys/mount.h> 101 #include <sys/syscallargs.h> 102 #include <sys/cpu.h> 103 #include <sys/atomic.h> 104 #include <sys/socketvar.h> 105 #include <sys/sleepq.h> 106 #include <sys/sysctl.h> 107 108 /* Flags for lwp::l_selflag. */ 109 #define SEL_RESET 0 /* awoken, interrupted, or not yet polling */ 110 #define SEL_SCANNING 1 /* polling descriptors */ 111 #define SEL_BLOCKING 2 /* blocking and waiting for event */ 112 #define SEL_EVENT 3 /* interrupted, events set directly */ 113 114 /* Operations: either select() or poll(). */ 115 #define SELOP_SELECT 1 116 #define SELOP_POLL 2 117 118 /* 119 * Per-cluster state for select()/poll(). For a system with fewer 120 * than 32 CPUs, this gives us per-CPU clusters. 121 */ 122 #define SELCLUSTERS 32 123 #define SELCLUSTERMASK (SELCLUSTERS - 1) 124 125 typedef struct selcluster { 126 kmutex_t *sc_lock; 127 sleepq_t sc_sleepq; 128 int sc_ncoll; 129 uint32_t sc_mask; 130 } selcluster_t; 131 132 static inline int selscan(char *, const int, const size_t, register_t *); 133 static inline int pollscan(struct pollfd *, const int, register_t *); 134 static void selclear(void); 135 136 static const int sel_flag[] = { 137 POLLRDNORM | POLLHUP | POLLERR, 138 POLLWRNORM | POLLHUP | POLLERR, 139 POLLRDBAND 140 }; 141 142 static syncobj_t select_sobj = { 143 .sobj_flag = SOBJ_SLEEPQ_FIFO, 144 .sobj_unsleep = sleepq_unsleep, 145 .sobj_changepri = sleepq_changepri, 146 .sobj_lendpri = sleepq_lendpri, 147 .sobj_owner = syncobj_noowner, 148 }; 149 150 static selcluster_t *selcluster[SELCLUSTERS] __read_mostly; 151 static int direct_select __read_mostly = 0; 152 153 /* 154 * Select system call. 155 */ 156 int 157 sys___pselect50(struct lwp *l, const struct sys___pselect50_args *uap, 158 register_t *retval) 159 { 160 /* { 161 syscallarg(int) nd; 162 syscallarg(fd_set *) in; 163 syscallarg(fd_set *) ou; 164 syscallarg(fd_set *) ex; 165 syscallarg(const struct timespec *) ts; 166 syscallarg(sigset_t *) mask; 167 } */ 168 struct timespec ats, *ts = NULL; 169 sigset_t amask, *mask = NULL; 170 int error; 171 172 if (SCARG(uap, ts)) { 173 error = copyin(SCARG(uap, ts), &ats, sizeof(ats)); 174 if (error) 175 return error; 176 ts = &ats; 177 } 178 if (SCARG(uap, mask) != NULL) { 179 error = copyin(SCARG(uap, mask), &amask, sizeof(amask)); 180 if (error) 181 return error; 182 mask = &amask; 183 } 184 185 return selcommon(retval, SCARG(uap, nd), SCARG(uap, in), 186 SCARG(uap, ou), SCARG(uap, ex), ts, mask); 187 } 188 189 int 190 sys___select50(struct lwp *l, const struct sys___select50_args *uap, 191 register_t *retval) 192 { 193 /* { 194 syscallarg(int) nd; 195 syscallarg(fd_set *) in; 196 syscallarg(fd_set *) ou; 197 syscallarg(fd_set *) ex; 198 syscallarg(struct timeval *) tv; 199 } */ 200 struct timeval atv; 201 struct timespec ats, *ts = NULL; 202 int error; 203 204 if (SCARG(uap, tv)) { 205 error = copyin(SCARG(uap, tv), (void *)&atv, sizeof(atv)); 206 if (error) 207 return error; 208 209 if (atv.tv_usec < 0 || atv.tv_usec >= 1000000) 210 return EINVAL; 211 212 TIMEVAL_TO_TIMESPEC(&atv, &ats); 213 ts = &ats; 214 } 215 216 return selcommon(retval, SCARG(uap, nd), SCARG(uap, in), 217 SCARG(uap, ou), SCARG(uap, ex), ts, NULL); 218 } 219 220 /* 221 * sel_do_scan: common code to perform the scan on descriptors. 222 */ 223 static int 224 sel_do_scan(const int op, void *fds, const int nf, const size_t ni, 225 struct timespec *ts, sigset_t *mask, register_t *retval) 226 { 227 lwp_t * const l = curlwp; 228 selcluster_t *sc; 229 kmutex_t *lock; 230 struct timespec sleepts; 231 int error, timo; 232 233 timo = 0; 234 if (ts && inittimeleft(ts, &sleepts) == -1) { 235 return EINVAL; 236 } 237 238 if (__predict_false(mask)) 239 sigsuspendsetup(l, mask); 240 241 sc = curcpu()->ci_data.cpu_selcluster; 242 lock = sc->sc_lock; 243 l->l_selcluster = sc; 244 if (op == SELOP_SELECT) { 245 l->l_selbits = fds; 246 l->l_selni = ni; 247 } else { 248 l->l_selbits = NULL; 249 } 250 251 for (;;) { 252 int ncoll; 253 254 SLIST_INIT(&l->l_selwait); 255 l->l_selret = 0; 256 257 /* 258 * No need to lock. If this is overwritten by another value 259 * while scanning, we will retry below. We only need to see 260 * exact state from the descriptors that we are about to poll, 261 * and lock activity resulting from fo_poll is enough to 262 * provide an up to date value for new polling activity. 263 */ 264 l->l_selflag = SEL_SCANNING; 265 ncoll = sc->sc_ncoll; 266 267 if (op == SELOP_SELECT) { 268 error = selscan((char *)fds, nf, ni, retval); 269 } else { 270 error = pollscan((struct pollfd *)fds, nf, retval); 271 } 272 if (error || *retval) 273 break; 274 if (ts && (timo = gettimeleft(ts, &sleepts)) <= 0) 275 break; 276 /* 277 * Acquire the lock and perform the (re)checks. Note, if 278 * collision has occured, then our state does not matter, 279 * as we must perform re-scan. Therefore, check it first. 280 */ 281 state_check: 282 mutex_spin_enter(lock); 283 if (__predict_false(sc->sc_ncoll != ncoll)) { 284 /* Collision: perform re-scan. */ 285 mutex_spin_exit(lock); 286 selclear(); 287 continue; 288 } 289 if (__predict_true(l->l_selflag == SEL_EVENT)) { 290 /* Events occured, they are set directly. */ 291 mutex_spin_exit(lock); 292 break; 293 } 294 if (__predict_true(l->l_selflag == SEL_RESET)) { 295 /* Events occured, but re-scan is requested. */ 296 mutex_spin_exit(lock); 297 selclear(); 298 continue; 299 } 300 /* Nothing happen, therefore - sleep. */ 301 l->l_selflag = SEL_BLOCKING; 302 l->l_kpriority = true; 303 sleepq_enter(&sc->sc_sleepq, l, lock); 304 sleepq_enqueue(&sc->sc_sleepq, sc, "select", &select_sobj); 305 error = sleepq_block(timo, true); 306 if (error != 0) { 307 break; 308 } 309 /* Awoken: need to check the state. */ 310 goto state_check; 311 } 312 selclear(); 313 314 /* Add direct events if any. */ 315 if (l->l_selflag == SEL_EVENT) { 316 KASSERT(l->l_selret != 0); 317 *retval += l->l_selret; 318 } 319 320 if (__predict_false(mask)) 321 sigsuspendteardown(l); 322 323 /* select and poll are not restarted after signals... */ 324 if (error == ERESTART) 325 return EINTR; 326 if (error == EWOULDBLOCK) 327 return 0; 328 return error; 329 } 330 331 int 332 selcommon(register_t *retval, int nd, fd_set *u_in, fd_set *u_ou, 333 fd_set *u_ex, struct timespec *ts, sigset_t *mask) 334 { 335 char smallbits[howmany(FD_SETSIZE, NFDBITS) * 336 sizeof(fd_mask) * 6]; 337 char *bits; 338 int error, nf; 339 size_t ni; 340 341 if (nd < 0) 342 return (EINVAL); 343 nf = curlwp->l_fd->fd_dt->dt_nfiles; 344 if (nd > nf) { 345 /* forgiving; slightly wrong */ 346 nd = nf; 347 } 348 ni = howmany(nd, NFDBITS) * sizeof(fd_mask); 349 if (ni * 6 > sizeof(smallbits)) 350 bits = kmem_alloc(ni * 6, KM_SLEEP); 351 else 352 bits = smallbits; 353 354 #define getbits(name, x) \ 355 if (u_ ## name) { \ 356 error = copyin(u_ ## name, bits + ni * x, ni); \ 357 if (error) \ 358 goto fail; \ 359 } else \ 360 memset(bits + ni * x, 0, ni); 361 getbits(in, 0); 362 getbits(ou, 1); 363 getbits(ex, 2); 364 #undef getbits 365 366 error = sel_do_scan(SELOP_SELECT, bits, nd, ni, ts, mask, retval); 367 if (error == 0 && u_in != NULL) 368 error = copyout(bits + ni * 3, u_in, ni); 369 if (error == 0 && u_ou != NULL) 370 error = copyout(bits + ni * 4, u_ou, ni); 371 if (error == 0 && u_ex != NULL) 372 error = copyout(bits + ni * 5, u_ex, ni); 373 fail: 374 if (bits != smallbits) 375 kmem_free(bits, ni * 6); 376 return (error); 377 } 378 379 static inline int 380 selscan(char *bits, const int nfd, const size_t ni, register_t *retval) 381 { 382 fd_mask *ibitp, *obitp; 383 int msk, i, j, fd, n; 384 file_t *fp; 385 386 ibitp = (fd_mask *)(bits + ni * 0); 387 obitp = (fd_mask *)(bits + ni * 3); 388 n = 0; 389 390 memset(obitp, 0, ni * 3); 391 for (msk = 0; msk < 3; msk++) { 392 for (i = 0; i < nfd; i += NFDBITS) { 393 fd_mask ibits, obits; 394 395 ibits = *ibitp; 396 obits = 0; 397 while ((j = ffs(ibits)) && (fd = i + --j) < nfd) { 398 ibits &= ~(1U << j); 399 if ((fp = fd_getfile(fd)) == NULL) 400 return (EBADF); 401 /* 402 * Setup an argument to selrecord(), which is 403 * a file descriptor number. 404 */ 405 curlwp->l_selrec = fd; 406 if ((*fp->f_ops->fo_poll)(fp, sel_flag[msk])) { 407 obits |= (1U << j); 408 n++; 409 } 410 fd_putfile(fd); 411 } 412 if (obits != 0) { 413 if (direct_select) { 414 kmutex_t *lock; 415 lock = curlwp->l_selcluster->sc_lock; 416 mutex_spin_enter(lock); 417 *obitp |= obits; 418 mutex_spin_exit(lock); 419 } else { 420 *obitp |= obits; 421 } 422 } 423 ibitp++; 424 obitp++; 425 } 426 } 427 *retval = n; 428 return (0); 429 } 430 431 /* 432 * Poll system call. 433 */ 434 int 435 sys_poll(struct lwp *l, const struct sys_poll_args *uap, register_t *retval) 436 { 437 /* { 438 syscallarg(struct pollfd *) fds; 439 syscallarg(u_int) nfds; 440 syscallarg(int) timeout; 441 } */ 442 struct timespec ats, *ts = NULL; 443 444 if (SCARG(uap, timeout) != INFTIM) { 445 ats.tv_sec = SCARG(uap, timeout) / 1000; 446 ats.tv_nsec = (SCARG(uap, timeout) % 1000) * 1000000; 447 ts = &ats; 448 } 449 450 return pollcommon(retval, SCARG(uap, fds), SCARG(uap, nfds), ts, NULL); 451 } 452 453 /* 454 * Poll system call. 455 */ 456 int 457 sys___pollts50(struct lwp *l, const struct sys___pollts50_args *uap, 458 register_t *retval) 459 { 460 /* { 461 syscallarg(struct pollfd *) fds; 462 syscallarg(u_int) nfds; 463 syscallarg(const struct timespec *) ts; 464 syscallarg(const sigset_t *) mask; 465 } */ 466 struct timespec ats, *ts = NULL; 467 sigset_t amask, *mask = NULL; 468 int error; 469 470 if (SCARG(uap, ts)) { 471 error = copyin(SCARG(uap, ts), &ats, sizeof(ats)); 472 if (error) 473 return error; 474 ts = &ats; 475 } 476 if (SCARG(uap, mask)) { 477 error = copyin(SCARG(uap, mask), &amask, sizeof(amask)); 478 if (error) 479 return error; 480 mask = &amask; 481 } 482 483 return pollcommon(retval, SCARG(uap, fds), SCARG(uap, nfds), ts, mask); 484 } 485 486 int 487 pollcommon(register_t *retval, struct pollfd *u_fds, u_int nfds, 488 struct timespec *ts, sigset_t *mask) 489 { 490 struct pollfd smallfds[32]; 491 struct pollfd *fds; 492 int error; 493 size_t ni; 494 495 if (nfds > curlwp->l_proc->p_rlimit[RLIMIT_NOFILE].rlim_max + 1000) { 496 /* 497 * Prevent userland from causing over-allocation. 498 * Raising the default limit too high can still cause 499 * a lot of memory to be allocated, but this also means 500 * that the file descriptor array will also be large. 501 * 502 * To reduce the memory requirements here, we could 503 * process the 'fds' array in chunks, but that 504 * is a lot of code that isn't normally useful. 505 * (Or just move the copyin/out into pollscan().) 506 * 507 * Historically the code silently truncated 'fds' to 508 * dt_nfiles entries - but that does cause issues. 509 * 510 * Using the max limit equivalent to sysctl 511 * kern.maxfiles is the moral equivalent of OPEN_MAX 512 * as specified by POSIX. 513 * 514 * We add a slop of 1000 in case the resource limit was 515 * changed after opening descriptors or the same descriptor 516 * was specified more than once. 517 */ 518 return EINVAL; 519 } 520 ni = nfds * sizeof(struct pollfd); 521 if (ni > sizeof(smallfds)) 522 fds = kmem_alloc(ni, KM_SLEEP); 523 else 524 fds = smallfds; 525 526 error = copyin(u_fds, fds, ni); 527 if (error) 528 goto fail; 529 530 error = sel_do_scan(SELOP_POLL, fds, nfds, ni, ts, mask, retval); 531 if (error == 0) 532 error = copyout(fds, u_fds, ni); 533 fail: 534 if (fds != smallfds) 535 kmem_free(fds, ni); 536 return (error); 537 } 538 539 static inline int 540 pollscan(struct pollfd *fds, const int nfd, register_t *retval) 541 { 542 file_t *fp; 543 int i, n = 0, revents; 544 545 for (i = 0; i < nfd; i++, fds++) { 546 fds->revents = 0; 547 if (fds->fd < 0) { 548 revents = 0; 549 } else if ((fp = fd_getfile(fds->fd)) == NULL) { 550 revents = POLLNVAL; 551 } else { 552 /* 553 * Perform poll: registers select request or returns 554 * the events which are set. Setup an argument for 555 * selrecord(), which is a pointer to struct pollfd. 556 */ 557 curlwp->l_selrec = (uintptr_t)fds; 558 revents = (*fp->f_ops->fo_poll)(fp, 559 fds->events | POLLERR | POLLHUP); 560 fd_putfile(fds->fd); 561 } 562 if (revents) { 563 fds->revents = revents; 564 n++; 565 } 566 } 567 *retval = n; 568 return (0); 569 } 570 571 int 572 seltrue(dev_t dev, int events, lwp_t *l) 573 { 574 575 return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)); 576 } 577 578 /* 579 * Record a select request. Concurrency issues: 580 * 581 * The caller holds the same lock across calls to selrecord() and 582 * selnotify(), so we don't need to consider a concurrent wakeup 583 * while in this routine. 584 * 585 * The only activity we need to guard against is selclear(), called by 586 * another thread that is exiting sel_do_scan(). 587 * `sel_lwp' can only become non-NULL while the caller's lock is held, 588 * so it cannot become non-NULL due to a change made by another thread 589 * while we are in this routine. It can only become _NULL_ due to a 590 * call to selclear(). 591 * 592 * If it is non-NULL and != selector there is the potential for 593 * selclear() to be called by another thread. If either of those 594 * conditions are true, we're not interested in touching the `named 595 * waiter' part of the selinfo record because we need to record a 596 * collision. Hence there is no need for additional locking in this 597 * routine. 598 */ 599 void 600 selrecord(lwp_t *selector, struct selinfo *sip) 601 { 602 selcluster_t *sc; 603 lwp_t *other; 604 605 KASSERT(selector == curlwp); 606 607 sc = selector->l_selcluster; 608 other = sip->sel_lwp; 609 610 if (other == selector) { 611 /* 1. We (selector) already claimed to be the first LWP. */ 612 KASSERT(sip->sel_cluster == sc); 613 } else if (other == NULL) { 614 /* 615 * 2. No first LWP, therefore we (selector) are the first. 616 * 617 * There may be unnamed waiters (collisions). Issue a memory 618 * barrier to ensure that we access sel_lwp (above) before 619 * other fields - this guards against a call to selclear(). 620 */ 621 membar_enter(); 622 sip->sel_lwp = selector; 623 SLIST_INSERT_HEAD(&selector->l_selwait, sip, sel_chain); 624 /* Copy the argument, which is for selnotify(). */ 625 sip->sel_fdinfo = selector->l_selrec; 626 /* Replace selinfo's lock with the chosen cluster's lock. */ 627 sip->sel_cluster = sc; 628 } else { 629 /* 3. Multiple waiters: record a collision. */ 630 sip->sel_collision |= sc->sc_mask; 631 KASSERT(sip->sel_cluster != NULL); 632 } 633 } 634 635 /* 636 * sel_setevents: a helper function for selnotify(), to set the events 637 * for LWP sleeping in selcommon() or pollcommon(). 638 */ 639 static inline bool 640 sel_setevents(lwp_t *l, struct selinfo *sip, const int events) 641 { 642 const int oflag = l->l_selflag; 643 int ret = 0; 644 645 /* 646 * If we require re-scan or it was required by somebody else, 647 * then just (re)set SEL_RESET and return. 648 */ 649 if (__predict_false(events == 0 || oflag == SEL_RESET)) { 650 l->l_selflag = SEL_RESET; 651 return true; 652 } 653 /* 654 * Direct set. Note: select state of LWP is locked. First, 655 * determine whether it is selcommon() or pollcommon(). 656 */ 657 if (l->l_selbits != NULL) { 658 const size_t ni = l->l_selni; 659 fd_mask *fds = (fd_mask *)l->l_selbits; 660 fd_mask *ofds = (fd_mask *)((char *)fds + ni * 3); 661 const int fd = sip->sel_fdinfo, fbit = 1 << (fd & __NFDMASK); 662 const int idx = fd >> __NFDSHIFT; 663 int n; 664 665 for (n = 0; n < 3; n++) { 666 if ((fds[idx] & fbit) != 0 && 667 (ofds[idx] & fbit) == 0 && 668 (sel_flag[n] & events)) { 669 ofds[idx] |= fbit; 670 ret++; 671 } 672 fds = (fd_mask *)((char *)fds + ni); 673 ofds = (fd_mask *)((char *)ofds + ni); 674 } 675 } else { 676 struct pollfd *pfd = (void *)sip->sel_fdinfo; 677 int revents = events & (pfd->events | POLLERR | POLLHUP); 678 679 if (revents) { 680 if (pfd->revents == 0) 681 ret = 1; 682 pfd->revents |= revents; 683 } 684 } 685 /* Check whether there are any events to return. */ 686 if (!ret) { 687 return false; 688 } 689 /* Indicate direct set and note the event (cluster lock is held). */ 690 l->l_selflag = SEL_EVENT; 691 l->l_selret += ret; 692 return true; 693 } 694 695 /* 696 * Do a wakeup when a selectable event occurs. Concurrency issues: 697 * 698 * As per selrecord(), the caller's object lock is held. If there 699 * is a named waiter, we must acquire the associated selcluster's lock 700 * in order to synchronize with selclear() and pollers going to sleep 701 * in sel_do_scan(). 702 * 703 * sip->sel_cluser cannot change at this point, as it is only changed 704 * in selrecord(), and concurrent calls to selrecord() are locked 705 * out by the caller. 706 */ 707 void 708 selnotify(struct selinfo *sip, int events, long knhint) 709 { 710 selcluster_t *sc; 711 uint32_t mask; 712 int index, oflag; 713 lwp_t *l; 714 kmutex_t *lock; 715 716 KNOTE(&sip->sel_klist, knhint); 717 718 if (sip->sel_lwp != NULL) { 719 /* One named LWP is waiting. */ 720 sc = sip->sel_cluster; 721 lock = sc->sc_lock; 722 mutex_spin_enter(lock); 723 /* Still there? */ 724 if (sip->sel_lwp != NULL) { 725 /* 726 * Set the events for our LWP and indicate that. 727 * Otherwise, request for a full re-scan. 728 */ 729 l = sip->sel_lwp; 730 oflag = l->l_selflag; 731 732 if (!direct_select) { 733 l->l_selflag = SEL_RESET; 734 } else if (!sel_setevents(l, sip, events)) { 735 /* No events to return. */ 736 mutex_spin_exit(lock); 737 return; 738 } 739 740 /* 741 * If thread is sleeping, wake it up. If it's not 742 * yet asleep, it will notice the change in state 743 * and will re-poll the descriptors. 744 */ 745 if (oflag == SEL_BLOCKING && l->l_mutex == lock) { 746 KASSERT(l->l_wchan == sc); 747 sleepq_unsleep(l, false); 748 } 749 } 750 mutex_spin_exit(lock); 751 } 752 753 if ((mask = sip->sel_collision) != 0) { 754 /* 755 * There was a collision (multiple waiters): we must 756 * inform all potentially interested waiters. 757 */ 758 sip->sel_collision = 0; 759 do { 760 index = ffs(mask) - 1; 761 mask &= ~(1U << index); 762 sc = selcluster[index]; 763 lock = sc->sc_lock; 764 mutex_spin_enter(lock); 765 sc->sc_ncoll++; 766 sleepq_wake(&sc->sc_sleepq, sc, (u_int)-1, lock); 767 } while (__predict_false(mask != 0)); 768 } 769 } 770 771 /* 772 * Remove an LWP from all objects that it is waiting for. Concurrency 773 * issues: 774 * 775 * The object owner's (e.g. device driver) lock is not held here. Calls 776 * can be made to selrecord() and we do not synchronize against those 777 * directly using locks. However, we use `sel_lwp' to lock out changes. 778 * Before clearing it we must use memory barriers to ensure that we can 779 * safely traverse the list of selinfo records. 780 */ 781 static void 782 selclear(void) 783 { 784 struct selinfo *sip, *next; 785 selcluster_t *sc; 786 lwp_t *l; 787 kmutex_t *lock; 788 789 l = curlwp; 790 sc = l->l_selcluster; 791 lock = sc->sc_lock; 792 793 mutex_spin_enter(lock); 794 for (sip = SLIST_FIRST(&l->l_selwait); sip != NULL; sip = next) { 795 KASSERT(sip->sel_lwp == l); 796 KASSERT(sip->sel_cluster == l->l_selcluster); 797 798 /* 799 * Read link to next selinfo record, if any. 800 * It's no longer safe to touch `sip' after clearing 801 * `sel_lwp', so ensure that the read of `sel_chain' 802 * completes before the clearing of sel_lwp becomes 803 * globally visible. 804 */ 805 next = SLIST_NEXT(sip, sel_chain); 806 membar_exit(); 807 /* Release the record for another named waiter to use. */ 808 sip->sel_lwp = NULL; 809 } 810 mutex_spin_exit(lock); 811 } 812 813 /* 814 * Initialize the select/poll system calls. Called once for each 815 * CPU in the system, as they are attached. 816 */ 817 void 818 selsysinit(struct cpu_info *ci) 819 { 820 selcluster_t *sc; 821 u_int index; 822 823 /* If already a cluster in place for this bit, re-use. */ 824 index = cpu_index(ci) & SELCLUSTERMASK; 825 sc = selcluster[index]; 826 if (sc == NULL) { 827 sc = kmem_alloc(roundup2(sizeof(selcluster_t), 828 coherency_unit) + coherency_unit, KM_SLEEP); 829 sc = (void *)roundup2((uintptr_t)sc, coherency_unit); 830 sc->sc_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_SCHED); 831 sleepq_init(&sc->sc_sleepq); 832 sc->sc_ncoll = 0; 833 sc->sc_mask = __BIT(index); 834 selcluster[index] = sc; 835 } 836 ci->ci_data.cpu_selcluster = sc; 837 } 838 839 /* 840 * Initialize a selinfo record. 841 */ 842 void 843 selinit(struct selinfo *sip) 844 { 845 846 memset(sip, 0, sizeof(*sip)); 847 } 848 849 /* 850 * Destroy a selinfo record. The owning object must not gain new 851 * references while this is in progress: all activity on the record 852 * must be stopped. 853 * 854 * Concurrency issues: we only need guard against a call to selclear() 855 * by a thread exiting sel_do_scan(). The caller has prevented further 856 * references being made to the selinfo record via selrecord(), and it 857 * will not call selnotify() again. 858 */ 859 void 860 seldestroy(struct selinfo *sip) 861 { 862 selcluster_t *sc; 863 kmutex_t *lock; 864 lwp_t *l; 865 866 if (sip->sel_lwp == NULL) 867 return; 868 869 /* 870 * Lock out selclear(). The selcluster pointer can't change while 871 * we are here since it is only ever changed in selrecord(), 872 * and that will not be entered again for this record because 873 * it is dying. 874 */ 875 KASSERT(sip->sel_cluster != NULL); 876 sc = sip->sel_cluster; 877 lock = sc->sc_lock; 878 mutex_spin_enter(lock); 879 if ((l = sip->sel_lwp) != NULL) { 880 /* 881 * This should rarely happen, so although SLIST_REMOVE() 882 * is slow, using it here is not a problem. 883 */ 884 KASSERT(l->l_selcluster == sc); 885 SLIST_REMOVE(&l->l_selwait, sip, selinfo, sel_chain); 886 sip->sel_lwp = NULL; 887 } 888 mutex_spin_exit(lock); 889 } 890 891 /* 892 * System control nodes. 893 */ 894 SYSCTL_SETUP(sysctl_select_setup, "sysctl select setup") 895 { 896 897 sysctl_createv(clog, 0, NULL, NULL, 898 CTLFLAG_PERMANENT | CTLFLAG_READWRITE, 899 CTLTYPE_INT, "direct_select", 900 SYSCTL_DESCR("Enable/disable direct select (for testing)"), 901 NULL, 0, &direct_select, 0, 902 CTL_KERN, CTL_CREATE, CTL_EOL); 903 } 904