1 /* $NetBSD: sys_select.c,v 1.33 2011/05/28 15:33:41 christos 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 1.33 2011/05/28 15:33:41 christos 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> 106 107 /* Flags for lwp::l_selflag. */ 108 #define SEL_RESET 0 /* awoken, interrupted, or not yet polling */ 109 #define SEL_SCANNING 1 /* polling descriptors */ 110 #define SEL_BLOCKING 2 /* blocking and waiting for event */ 111 #define SEL_EVENT 3 /* interrupted, events set directly */ 112 113 /* Operations: either select() or poll(). */ 114 #define SELOP_SELECT 1 115 #define SELOP_POLL 2 116 117 /* 118 * Per-cluster state for select()/poll(). For a system with fewer 119 * than 32 CPUs, this gives us per-CPU clusters. 120 */ 121 #define SELCLUSTERS 32 122 #define SELCLUSTERMASK (SELCLUSTERS - 1) 123 124 typedef struct selcluster { 125 kmutex_t *sc_lock; 126 sleepq_t sc_sleepq; 127 int sc_ncoll; 128 uint32_t sc_mask; 129 } selcluster_t; 130 131 static inline int selscan(char *, const int, const size_t, register_t *); 132 static inline int pollscan(struct pollfd *, const int, register_t *); 133 static void selclear(void); 134 135 static const int sel_flag[] = { 136 POLLRDNORM | POLLHUP | POLLERR, 137 POLLWRNORM | POLLHUP | POLLERR, 138 POLLRDBAND 139 }; 140 141 static syncobj_t select_sobj = { 142 SOBJ_SLEEPQ_FIFO, 143 sleepq_unsleep, 144 sleepq_changepri, 145 sleepq_lendpri, 146 syncobj_noowner, 147 }; 148 149 static selcluster_t *selcluster[SELCLUSTERS] __read_mostly; 150 151 /* 152 * Select system call. 153 */ 154 int 155 sys___pselect50(struct lwp *l, const struct sys___pselect50_args *uap, 156 register_t *retval) 157 { 158 /* { 159 syscallarg(int) nd; 160 syscallarg(fd_set *) in; 161 syscallarg(fd_set *) ou; 162 syscallarg(fd_set *) ex; 163 syscallarg(const struct timespec *) ts; 164 syscallarg(sigset_t *) mask; 165 } */ 166 struct timespec ats, *ts = NULL; 167 sigset_t amask, *mask = NULL; 168 int error; 169 170 if (SCARG(uap, ts)) { 171 error = copyin(SCARG(uap, ts), &ats, sizeof(ats)); 172 if (error) 173 return error; 174 ts = &ats; 175 } 176 if (SCARG(uap, mask) != NULL) { 177 error = copyin(SCARG(uap, mask), &amask, sizeof(amask)); 178 if (error) 179 return error; 180 mask = &amask; 181 } 182 183 return selcommon(retval, SCARG(uap, nd), SCARG(uap, in), 184 SCARG(uap, ou), SCARG(uap, ex), ts, mask); 185 } 186 187 int 188 sys___select50(struct lwp *l, const struct sys___select50_args *uap, 189 register_t *retval) 190 { 191 /* { 192 syscallarg(int) nd; 193 syscallarg(fd_set *) in; 194 syscallarg(fd_set *) ou; 195 syscallarg(fd_set *) ex; 196 syscallarg(struct timeval *) tv; 197 } */ 198 struct timeval atv; 199 struct timespec ats, *ts = NULL; 200 int error; 201 202 if (SCARG(uap, tv)) { 203 error = copyin(SCARG(uap, tv), (void *)&atv, sizeof(atv)); 204 if (error) 205 return error; 206 TIMEVAL_TO_TIMESPEC(&atv, &ats); 207 ts = &ats; 208 } 209 210 return selcommon(retval, SCARG(uap, nd), SCARG(uap, in), 211 SCARG(uap, ou), SCARG(uap, ex), ts, NULL); 212 } 213 214 /* 215 * sel_do_scan: common code to perform the scan on descriptors. 216 */ 217 static int 218 sel_do_scan(const int op, void *fds, const int nf, const size_t ni, 219 struct timespec *ts, sigset_t *mask, register_t *retval) 220 { 221 lwp_t * const l = curlwp; 222 selcluster_t *sc; 223 kmutex_t *lock; 224 struct timespec sleepts; 225 int error, timo; 226 227 timo = 0; 228 if (ts && inittimeleft(ts, &sleepts) == -1) { 229 return EINVAL; 230 } 231 232 if (__predict_false(mask)) 233 sigsuspendsetup(l, mask); 234 235 sc = curcpu()->ci_data.cpu_selcluster; 236 lock = sc->sc_lock; 237 l->l_selcluster = sc; 238 SLIST_INIT(&l->l_selwait); 239 240 l->l_selret = 0; 241 if (op == SELOP_SELECT) { 242 l->l_selbits = fds; 243 l->l_selni = ni; 244 } else { 245 l->l_selbits = NULL; 246 } 247 for (;;) { 248 int ncoll; 249 250 /* 251 * No need to lock. If this is overwritten by another value 252 * while scanning, we will retry below. We only need to see 253 * exact state from the descriptors that we are about to poll, 254 * and lock activity resulting from fo_poll is enough to 255 * provide an up to date value for new polling activity. 256 */ 257 l->l_selflag = SEL_SCANNING; 258 ncoll = sc->sc_ncoll; 259 260 if (op == SELOP_SELECT) { 261 error = selscan((char *)fds, nf, ni, retval); 262 } else { 263 error = pollscan((struct pollfd *)fds, nf, retval); 264 } 265 if (error || *retval) 266 break; 267 if (ts && (timo = gettimeleft(ts, &sleepts)) <= 0) 268 break; 269 /* 270 * Acquire the lock and perform the (re)checks. Note, if 271 * collision has occured, then our state does not matter, 272 * as we must perform re-scan. Therefore, check it first. 273 */ 274 state_check: 275 mutex_spin_enter(lock); 276 if (__predict_false(sc->sc_ncoll != ncoll)) { 277 /* Collision: perform re-scan. */ 278 mutex_spin_exit(lock); 279 continue; 280 } 281 if (__predict_true(l->l_selflag == SEL_EVENT)) { 282 /* Events occured, they are set directly. */ 283 mutex_spin_exit(lock); 284 KASSERT(l->l_selret != 0); 285 *retval = l->l_selret; 286 break; 287 } 288 if (__predict_true(l->l_selflag == SEL_RESET)) { 289 /* Events occured, but re-scan is requested. */ 290 mutex_spin_exit(lock); 291 continue; 292 } 293 /* Nothing happen, therefore - sleep. */ 294 l->l_selflag = SEL_BLOCKING; 295 l->l_kpriority = true; 296 sleepq_enter(&sc->sc_sleepq, l, lock); 297 sleepq_enqueue(&sc->sc_sleepq, sc, "select", &select_sobj); 298 error = sleepq_block(timo, true); 299 if (error != 0) { 300 break; 301 } 302 /* Awoken: need to check the state. */ 303 goto state_check; 304 } 305 selclear(); 306 307 if (__predict_false(mask)) 308 sigsuspendteardown(l); 309 310 /* select and poll are not restarted after signals... */ 311 if (error == ERESTART) 312 return EINTR; 313 if (error == EWOULDBLOCK) 314 return 0; 315 return error; 316 } 317 318 int 319 selcommon(register_t *retval, int nd, fd_set *u_in, fd_set *u_ou, 320 fd_set *u_ex, struct timespec *ts, sigset_t *mask) 321 { 322 char smallbits[howmany(FD_SETSIZE, NFDBITS) * 323 sizeof(fd_mask) * 6]; 324 char *bits; 325 int error, nf; 326 size_t ni; 327 328 if (nd < 0) 329 return (EINVAL); 330 nf = curlwp->l_fd->fd_dt->dt_nfiles; 331 if (nd > nf) { 332 /* forgiving; slightly wrong */ 333 nd = nf; 334 } 335 ni = howmany(nd, NFDBITS) * sizeof(fd_mask); 336 if (ni * 6 > sizeof(smallbits)) { 337 bits = kmem_alloc(ni * 6, KM_SLEEP); 338 if (bits == NULL) 339 return ENOMEM; 340 } else 341 bits = smallbits; 342 343 #define getbits(name, x) \ 344 if (u_ ## name) { \ 345 error = copyin(u_ ## name, bits + ni * x, ni); \ 346 if (error) \ 347 goto fail; \ 348 } else \ 349 memset(bits + ni * x, 0, ni); 350 getbits(in, 0); 351 getbits(ou, 1); 352 getbits(ex, 2); 353 #undef getbits 354 355 error = sel_do_scan(SELOP_SELECT, bits, nd, ni, ts, mask, retval); 356 if (error == 0 && u_in != NULL) 357 error = copyout(bits + ni * 3, u_in, ni); 358 if (error == 0 && u_ou != NULL) 359 error = copyout(bits + ni * 4, u_ou, ni); 360 if (error == 0 && u_ex != NULL) 361 error = copyout(bits + ni * 5, u_ex, ni); 362 fail: 363 if (bits != smallbits) 364 kmem_free(bits, ni * 6); 365 return (error); 366 } 367 368 static inline int 369 selscan(char *bits, const int nfd, const size_t ni, register_t *retval) 370 { 371 fd_mask *ibitp, *obitp; 372 int msk, i, j, fd, n; 373 file_t *fp; 374 375 ibitp = (fd_mask *)(bits + ni * 0); 376 obitp = (fd_mask *)(bits + ni * 3); 377 n = 0; 378 379 for (msk = 0; msk < 3; msk++) { 380 for (i = 0; i < nfd; i += NFDBITS) { 381 fd_mask ibits, obits; 382 383 ibits = *ibitp++; 384 obits = 0; 385 while ((j = ffs(ibits)) && (fd = i + --j) < nfd) { 386 ibits &= ~(1 << j); 387 if ((fp = fd_getfile(fd)) == NULL) 388 return (EBADF); 389 /* 390 * Setup an argument to selrecord(), which is 391 * a file descriptor number. 392 */ 393 curlwp->l_selrec = fd; 394 if ((*fp->f_ops->fo_poll)(fp, sel_flag[msk])) { 395 obits |= (1 << j); 396 n++; 397 } 398 fd_putfile(fd); 399 } 400 *obitp++ = obits; 401 } 402 } 403 *retval = n; 404 return (0); 405 } 406 407 /* 408 * Poll system call. 409 */ 410 int 411 sys_poll(struct lwp *l, const struct sys_poll_args *uap, register_t *retval) 412 { 413 /* { 414 syscallarg(struct pollfd *) fds; 415 syscallarg(u_int) nfds; 416 syscallarg(int) timeout; 417 } */ 418 struct timespec ats, *ts = NULL; 419 420 if (SCARG(uap, timeout) != INFTIM) { 421 ats.tv_sec = SCARG(uap, timeout) / 1000; 422 ats.tv_nsec = (SCARG(uap, timeout) % 1000) * 1000000; 423 ts = &ats; 424 } 425 426 return pollcommon(retval, SCARG(uap, fds), SCARG(uap, nfds), ts, NULL); 427 } 428 429 /* 430 * Poll system call. 431 */ 432 int 433 sys___pollts50(struct lwp *l, const struct sys___pollts50_args *uap, 434 register_t *retval) 435 { 436 /* { 437 syscallarg(struct pollfd *) fds; 438 syscallarg(u_int) nfds; 439 syscallarg(const struct timespec *) ts; 440 syscallarg(const sigset_t *) mask; 441 } */ 442 struct timespec ats, *ts = NULL; 443 sigset_t amask, *mask = NULL; 444 int error; 445 446 if (SCARG(uap, ts)) { 447 error = copyin(SCARG(uap, ts), &ats, sizeof(ats)); 448 if (error) 449 return error; 450 ts = &ats; 451 } 452 if (SCARG(uap, mask)) { 453 error = copyin(SCARG(uap, mask), &amask, sizeof(amask)); 454 if (error) 455 return error; 456 mask = &amask; 457 } 458 459 return pollcommon(retval, SCARG(uap, fds), SCARG(uap, nfds), ts, mask); 460 } 461 462 int 463 pollcommon(register_t *retval, struct pollfd *u_fds, u_int nfds, 464 struct timespec *ts, sigset_t *mask) 465 { 466 struct pollfd smallfds[32]; 467 struct pollfd *fds; 468 int error; 469 size_t ni; 470 471 if (nfds > 1000 + curlwp->l_fd->fd_dt->dt_nfiles) { 472 /* 473 * Either the user passed in a very sparse 'fds' or junk! 474 * The kmem_alloc() call below would be bad news. 475 * We could process the 'fds' array in chunks, but that 476 * is a lot of code that isn't normally useful. 477 * (Or just move the copyin/out into pollscan().) 478 * Historically the code silently truncated 'fds' to 479 * dt_nfiles entries - but that does cause issues. 480 */ 481 return EINVAL; 482 } 483 ni = nfds * sizeof(struct pollfd); 484 if (ni > sizeof(smallfds)) { 485 fds = kmem_alloc(ni, KM_SLEEP); 486 if (fds == NULL) 487 return ENOMEM; 488 } else 489 fds = smallfds; 490 491 error = copyin(u_fds, fds, ni); 492 if (error) 493 goto fail; 494 495 error = sel_do_scan(SELOP_POLL, fds, nfds, ni, ts, mask, retval); 496 if (error == 0) 497 error = copyout(fds, u_fds, ni); 498 fail: 499 if (fds != smallfds) 500 kmem_free(fds, ni); 501 return (error); 502 } 503 504 static inline int 505 pollscan(struct pollfd *fds, const int nfd, register_t *retval) 506 { 507 file_t *fp; 508 int i, n = 0; 509 510 for (i = 0; i < nfd; i++, fds++) { 511 if (fds->fd < 0) { 512 fds->revents = 0; 513 } else if ((fp = fd_getfile(fds->fd)) == NULL) { 514 fds->revents = POLLNVAL; 515 n++; 516 } else { 517 /* 518 * Perform poll: registers select request or returns 519 * the events which are set. Setup an argument for 520 * selrecord(), which is a pointer to struct pollfd. 521 */ 522 curlwp->l_selrec = (uintptr_t)fds; 523 fds->revents = (*fp->f_ops->fo_poll)(fp, 524 fds->events | POLLERR | POLLHUP); 525 if (fds->revents != 0) 526 n++; 527 fd_putfile(fds->fd); 528 } 529 } 530 *retval = n; 531 return (0); 532 } 533 534 int 535 seltrue(dev_t dev, int events, lwp_t *l) 536 { 537 538 return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)); 539 } 540 541 /* 542 * Record a select request. Concurrency issues: 543 * 544 * The caller holds the same lock across calls to selrecord() and 545 * selnotify(), so we don't need to consider a concurrent wakeup 546 * while in this routine. 547 * 548 * The only activity we need to guard against is selclear(), called by 549 * another thread that is exiting sel_do_scan(). 550 * `sel_lwp' can only become non-NULL while the caller's lock is held, 551 * so it cannot become non-NULL due to a change made by another thread 552 * while we are in this routine. It can only become _NULL_ due to a 553 * call to selclear(). 554 * 555 * If it is non-NULL and != selector there is the potential for 556 * selclear() to be called by another thread. If either of those 557 * conditions are true, we're not interested in touching the `named 558 * waiter' part of the selinfo record because we need to record a 559 * collision. Hence there is no need for additional locking in this 560 * routine. 561 */ 562 void 563 selrecord(lwp_t *selector, struct selinfo *sip) 564 { 565 selcluster_t *sc; 566 lwp_t *other; 567 568 KASSERT(selector == curlwp); 569 570 sc = selector->l_selcluster; 571 other = sip->sel_lwp; 572 573 if (other == selector) { 574 /* 1. We (selector) already claimed to be the first LWP. */ 575 KASSERT(sip->sel_cluster = sc); 576 } else if (other == NULL) { 577 /* 578 * 2. No first LWP, therefore we (selector) are the first. 579 * 580 * There may be unnamed waiters (collisions). Issue a memory 581 * barrier to ensure that we access sel_lwp (above) before 582 * other fields - this guards against a call to selclear(). 583 */ 584 membar_enter(); 585 sip->sel_lwp = selector; 586 SLIST_INSERT_HEAD(&selector->l_selwait, sip, sel_chain); 587 /* Copy the argument, which is for selnotify(). */ 588 sip->sel_fdinfo = selector->l_selrec; 589 /* Replace selinfo's lock with the chosen cluster's lock. */ 590 sip->sel_cluster = sc; 591 } else { 592 /* 3. Multiple waiters: record a collision. */ 593 sip->sel_collision |= sc->sc_mask; 594 KASSERT(sip->sel_cluster != NULL); 595 } 596 } 597 598 /* 599 * sel_setevents: a helper function for selnotify(), to set the events 600 * for LWP sleeping in selcommon() or pollcommon(). 601 */ 602 static inline bool 603 sel_setevents(lwp_t *l, struct selinfo *sip, const int events) 604 { 605 const int oflag = l->l_selflag; 606 int ret = 0; 607 608 /* 609 * If we require re-scan or it was required by somebody else, 610 * then just (re)set SEL_RESET and return. 611 */ 612 if (__predict_false(events == 0 || oflag == SEL_RESET)) { 613 l->l_selflag = SEL_RESET; 614 return true; 615 } 616 /* 617 * Direct set. Note: select state of LWP is locked. First, 618 * determine whether it is selcommon() or pollcommon(). 619 */ 620 if (l->l_selbits != NULL) { 621 const size_t ni = l->l_selni; 622 fd_mask *fds = (fd_mask *)l->l_selbits; 623 fd_mask *ofds = (fd_mask *)((char *)fds + ni * 3); 624 const int fd = sip->sel_fdinfo, fbit = 1 << (fd & __NFDMASK); 625 const int idx = fd >> __NFDSHIFT; 626 int n; 627 628 for (n = 0; n < 3; n++) { 629 if ((fds[idx] & fbit) != 0 && (sel_flag[n] & events)) { 630 ofds[idx] |= fbit; 631 ret++; 632 } 633 fds = (fd_mask *)((char *)fds + ni); 634 ofds = (fd_mask *)((char *)ofds + ni); 635 } 636 } else { 637 struct pollfd *pfd = (void *)sip->sel_fdinfo; 638 int revents = events & (pfd->events | POLLERR | POLLHUP); 639 640 if (revents) { 641 pfd->revents |= revents; 642 ret = 1; 643 } 644 } 645 /* Check whether there are any events to return. */ 646 if (!ret) { 647 return false; 648 } 649 /* Indicate direct set and note the event (cluster lock is held). */ 650 l->l_selflag = SEL_EVENT; 651 l->l_selret += ret; 652 return true; 653 } 654 655 /* 656 * Do a wakeup when a selectable event occurs. Concurrency issues: 657 * 658 * As per selrecord(), the caller's object lock is held. If there 659 * is a named waiter, we must acquire the associated selcluster's lock 660 * in order to synchronize with selclear() and pollers going to sleep 661 * in sel_do_scan(). 662 * 663 * sip->sel_cluser cannot change at this point, as it is only changed 664 * in selrecord(), and concurrent calls to selrecord() are locked 665 * out by the caller. 666 */ 667 void 668 selnotify(struct selinfo *sip, int events, long knhint) 669 { 670 selcluster_t *sc; 671 uint32_t mask; 672 int index, oflag; 673 lwp_t *l; 674 kmutex_t *lock; 675 676 KNOTE(&sip->sel_klist, knhint); 677 678 if (sip->sel_lwp != NULL) { 679 /* One named LWP is waiting. */ 680 sc = sip->sel_cluster; 681 lock = sc->sc_lock; 682 mutex_spin_enter(lock); 683 /* Still there? */ 684 if (sip->sel_lwp != NULL) { 685 /* 686 * Set the events for our LWP and indicate that. 687 * Otherwise, request for a full re-scan. 688 */ 689 l = sip->sel_lwp; 690 oflag = l->l_selflag; 691 #ifndef NO_DIRECT_SELECT 692 if (!sel_setevents(l, sip, events)) { 693 /* No events to return. */ 694 mutex_spin_exit(lock); 695 return; 696 } 697 #else 698 l->l_selflag = SEL_RESET; 699 #endif 700 /* 701 * If thread is sleeping, wake it up. If it's not 702 * yet asleep, it will notice the change in state 703 * and will re-poll the descriptors. 704 */ 705 if (oflag == SEL_BLOCKING && l->l_mutex == lock) { 706 KASSERT(l->l_wchan == sc); 707 sleepq_unsleep(l, false); 708 } 709 } 710 mutex_spin_exit(lock); 711 } 712 713 if ((mask = sip->sel_collision) != 0) { 714 /* 715 * There was a collision (multiple waiters): we must 716 * inform all potentially interested waiters. 717 */ 718 sip->sel_collision = 0; 719 do { 720 index = ffs(mask) - 1; 721 mask &= ~(1 << index); 722 sc = selcluster[index]; 723 lock = sc->sc_lock; 724 mutex_spin_enter(lock); 725 sc->sc_ncoll++; 726 sleepq_wake(&sc->sc_sleepq, sc, (u_int)-1, lock); 727 } while (__predict_false(mask != 0)); 728 } 729 } 730 731 /* 732 * Remove an LWP from all objects that it is waiting for. Concurrency 733 * issues: 734 * 735 * The object owner's (e.g. device driver) lock is not held here. Calls 736 * can be made to selrecord() and we do not synchronize against those 737 * directly using locks. However, we use `sel_lwp' to lock out changes. 738 * Before clearing it we must use memory barriers to ensure that we can 739 * safely traverse the list of selinfo records. 740 */ 741 static void 742 selclear(void) 743 { 744 struct selinfo *sip, *next; 745 selcluster_t *sc; 746 lwp_t *l; 747 kmutex_t *lock; 748 749 l = curlwp; 750 sc = l->l_selcluster; 751 lock = sc->sc_lock; 752 753 mutex_spin_enter(lock); 754 for (sip = SLIST_FIRST(&l->l_selwait); sip != NULL; sip = next) { 755 KASSERT(sip->sel_lwp == l); 756 KASSERT(sip->sel_cluster == l->l_selcluster); 757 758 /* 759 * Read link to next selinfo record, if any. 760 * It's no longer safe to touch `sip' after clearing 761 * `sel_lwp', so ensure that the read of `sel_chain' 762 * completes before the clearing of sel_lwp becomes 763 * globally visible. 764 */ 765 next = SLIST_NEXT(sip, sel_chain); 766 membar_exit(); 767 /* Release the record for another named waiter to use. */ 768 sip->sel_lwp = NULL; 769 } 770 mutex_spin_exit(lock); 771 } 772 773 /* 774 * Initialize the select/poll system calls. Called once for each 775 * CPU in the system, as they are attached. 776 */ 777 void 778 selsysinit(struct cpu_info *ci) 779 { 780 selcluster_t *sc; 781 u_int index; 782 783 /* If already a cluster in place for this bit, re-use. */ 784 index = cpu_index(ci) & SELCLUSTERMASK; 785 sc = selcluster[index]; 786 if (sc == NULL) { 787 sc = kmem_alloc(roundup2(sizeof(selcluster_t), 788 coherency_unit) + coherency_unit, KM_SLEEP); 789 sc = (void *)roundup2((uintptr_t)sc, coherency_unit); 790 sc->sc_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_SCHED); 791 sleepq_init(&sc->sc_sleepq); 792 sc->sc_ncoll = 0; 793 sc->sc_mask = (1 << index); 794 selcluster[index] = sc; 795 } 796 ci->ci_data.cpu_selcluster = sc; 797 } 798 799 /* 800 * Initialize a selinfo record. 801 */ 802 void 803 selinit(struct selinfo *sip) 804 { 805 806 memset(sip, 0, sizeof(*sip)); 807 } 808 809 /* 810 * Destroy a selinfo record. The owning object must not gain new 811 * references while this is in progress: all activity on the record 812 * must be stopped. 813 * 814 * Concurrency issues: we only need guard against a call to selclear() 815 * by a thread exiting sel_do_scan(). The caller has prevented further 816 * references being made to the selinfo record via selrecord(), and it 817 * will not call selnotify() again. 818 */ 819 void 820 seldestroy(struct selinfo *sip) 821 { 822 selcluster_t *sc; 823 kmutex_t *lock; 824 lwp_t *l; 825 826 if (sip->sel_lwp == NULL) 827 return; 828 829 /* 830 * Lock out selclear(). The selcluster pointer can't change while 831 * we are here since it is only ever changed in selrecord(), 832 * and that will not be entered again for this record because 833 * it is dying. 834 */ 835 KASSERT(sip->sel_cluster != NULL); 836 sc = sip->sel_cluster; 837 lock = sc->sc_lock; 838 mutex_spin_enter(lock); 839 if ((l = sip->sel_lwp) != NULL) { 840 /* 841 * This should rarely happen, so although SLIST_REMOVE() 842 * is slow, using it here is not a problem. 843 */ 844 KASSERT(l->l_selcluster == sc); 845 SLIST_REMOVE(&l->l_selwait, sip, selinfo, sel_chain); 846 sip->sel_lwp = NULL; 847 } 848 mutex_spin_exit(lock); 849 } 850 851 int 852 pollsock(struct socket *so, const struct timespec *tsp, int events) 853 { 854 int ncoll, error, timo; 855 struct timespec sleepts, ts; 856 selcluster_t *sc; 857 lwp_t *l; 858 kmutex_t *lock; 859 860 timo = 0; 861 if (tsp != NULL) { 862 ts = *tsp; 863 if (inittimeleft(&ts, &sleepts) == -1) 864 return EINVAL; 865 } 866 867 l = curlwp; 868 sc = curcpu()->ci_data.cpu_selcluster; 869 lock = sc->sc_lock; 870 l->l_selcluster = sc; 871 SLIST_INIT(&l->l_selwait); 872 error = 0; 873 for (;;) { 874 /* 875 * No need to lock. If this is overwritten by another 876 * value while scanning, we will retry below. We only 877 * need to see exact state from the descriptors that 878 * we are about to poll, and lock activity resulting 879 * from fo_poll is enough to provide an up to date value 880 * for new polling activity. 881 */ 882 ncoll = sc->sc_ncoll; 883 l->l_selflag = SEL_SCANNING; 884 if (sopoll(so, events) != 0) 885 break; 886 if (tsp && (timo = gettimeleft(&ts, &sleepts)) <= 0) 887 break; 888 mutex_spin_enter(lock); 889 if (l->l_selflag != SEL_SCANNING || sc->sc_ncoll != ncoll) { 890 mutex_spin_exit(lock); 891 continue; 892 } 893 l->l_selflag = SEL_BLOCKING; 894 sleepq_enter(&sc->sc_sleepq, l, lock); 895 sleepq_enqueue(&sc->sc_sleepq, sc, "pollsock", &select_sobj); 896 error = sleepq_block(timo, true); 897 if (error != 0) 898 break; 899 } 900 selclear(); 901 /* poll is not restarted after signals... */ 902 if (error == ERESTART) 903 error = EINTR; 904 if (error == EWOULDBLOCK) 905 error = 0; 906 return (error); 907 } 908