1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 /*
27 * Copyright (c) 2012 by Delphix. All rights reserved.
28 * Copyright 2016 Joyent, Inc.
29 */
30
31 #include <sys/types.h>
32 #include <sys/devops.h>
33 #include <sys/conf.h>
34 #include <sys/modctl.h>
35 #include <sys/sunddi.h>
36 #include <sys/stat.h>
37 #include <sys/poll_impl.h>
38 #include <sys/errno.h>
39 #include <sys/kmem.h>
40 #include <sys/mkdev.h>
41 #include <sys/debug.h>
42 #include <sys/file.h>
43 #include <sys/sysmacros.h>
44 #include <sys/systm.h>
45 #include <sys/bitmap.h>
46 #include <sys/devpoll.h>
47 #include <sys/rctl.h>
48 #include <sys/resource.h>
49 #include <sys/schedctl.h>
50 #include <sys/epoll.h>
51
52 #define RESERVED 1
53
54 /* local data struct */
55 static dp_entry_t **devpolltbl; /* dev poll entries */
56 static size_t dptblsize;
57
58 static kmutex_t devpoll_lock; /* lock protecting dev tbl */
59 int devpoll_init; /* is /dev/poll initialized already */
60
61 /* device local functions */
62
63 static int dpopen(dev_t *devp, int flag, int otyp, cred_t *credp);
64 static int dpwrite(dev_t dev, struct uio *uiop, cred_t *credp);
65 static int dpioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp,
66 int *rvalp);
67 static int dppoll(dev_t dev, short events, int anyyet, short *reventsp,
68 struct pollhead **phpp);
69 static int dpclose(dev_t dev, int flag, int otyp, cred_t *credp);
70 static dev_info_t *dpdevi;
71
72
73 static struct cb_ops dp_cb_ops = {
74 dpopen, /* open */
75 dpclose, /* close */
76 nodev, /* strategy */
77 nodev, /* print */
78 nodev, /* dump */
79 nodev, /* read */
80 dpwrite, /* write */
81 dpioctl, /* ioctl */
82 nodev, /* devmap */
83 nodev, /* mmap */
84 nodev, /* segmap */
85 dppoll, /* poll */
86 ddi_prop_op, /* prop_op */
87 (struct streamtab *)0, /* streamtab */
88 D_MP, /* flags */
89 CB_REV, /* cb_ops revision */
90 nodev, /* aread */
91 nodev /* awrite */
92 };
93
94 static int dpattach(dev_info_t *, ddi_attach_cmd_t);
95 static int dpdetach(dev_info_t *, ddi_detach_cmd_t);
96 static int dpinfo(dev_info_t *, ddi_info_cmd_t, void *, void **);
97
98 static struct dev_ops dp_ops = {
99 DEVO_REV, /* devo_rev */
100 0, /* refcnt */
101 dpinfo, /* info */
102 nulldev, /* identify */
103 nulldev, /* probe */
104 dpattach, /* attach */
105 dpdetach, /* detach */
106 nodev, /* reset */
107 &dp_cb_ops, /* driver operations */
108 (struct bus_ops *)NULL, /* bus operations */
109 nulldev, /* power */
110 ddi_quiesce_not_needed, /* quiesce */
111 };
112
113
114 static struct modldrv modldrv = {
115 &mod_driverops, /* type of module - a driver */
116 "/dev/poll driver",
117 &dp_ops,
118 };
119
120 static struct modlinkage modlinkage = {
121 MODREV_1,
122 { (void *)&modldrv,
123 NULL }
124 };
125
126 static void pcachelink_assoc(pollcache_t *, pollcache_t *);
127 static void pcachelink_mark_stale(pollcache_t *);
128 static void pcachelink_purge_stale(pollcache_t *);
129 static void pcachelink_purge_all(pollcache_t *);
130
131
132 /*
133 * Locking Design
134 *
135 * The /dev/poll driver shares most of its code with poll sys call whose
136 * code is in common/syscall/poll.c. In poll(2) design, the pollcache
137 * structure is per lwp. An implicit assumption is made there that some
138 * portion of pollcache will never be touched by other lwps. E.g., in
139 * poll(2) design, no lwp will ever need to grow bitmap of other lwp.
140 * This assumption is not true for /dev/poll; hence the need for extra
141 * locking.
142 *
143 * To allow more parallelism, each /dev/poll file descriptor (indexed by
144 * minor number) has its own lock. Since read (dpioctl) is a much more
145 * frequent operation than write, we want to allow multiple reads on same
146 * /dev/poll fd. However, we prevent writes from being starved by giving
147 * priority to write operation. Theoretically writes can starve reads as
148 * well. But in practical sense this is not important because (1) writes
149 * happens less often than reads, and (2) write operation defines the
150 * content of poll fd a cache set. If writes happens so often that they
151 * can starve reads, that means the cached set is very unstable. It may
152 * not make sense to read an unstable cache set anyway. Therefore, the
153 * writers starving readers case is not handled in this design.
154 */
155
156 int
157 _init()
158 {
159 int error;
160
161 dptblsize = DEVPOLLSIZE;
162 devpolltbl = kmem_zalloc(sizeof (caddr_t) * dptblsize, KM_SLEEP);
163 mutex_init(&devpoll_lock, NULL, MUTEX_DEFAULT, NULL);
164 devpoll_init = 1;
165 if ((error = mod_install(&modlinkage)) != 0) {
166 kmem_free(devpolltbl, sizeof (caddr_t) * dptblsize);
167 devpoll_init = 0;
168 }
169 return (error);
170 }
171
172 int
173 _fini()
174 {
175 int error;
176
177 if ((error = mod_remove(&modlinkage)) != 0) {
178 return (error);
179 }
180 mutex_destroy(&devpoll_lock);
181 kmem_free(devpolltbl, sizeof (caddr_t) * dptblsize);
182 return (0);
183 }
184
185 int
186 _info(struct modinfo *modinfop)
187 {
188 return (mod_info(&modlinkage, modinfop));
189 }
190
191 /*ARGSUSED*/
192 static int
193 dpattach(dev_info_t *devi, ddi_attach_cmd_t cmd)
194 {
195 if (ddi_create_minor_node(devi, "poll", S_IFCHR, 0, DDI_PSEUDO, NULL)
196 == DDI_FAILURE) {
197 ddi_remove_minor_node(devi, NULL);
198 return (DDI_FAILURE);
199 }
200 dpdevi = devi;
201 return (DDI_SUCCESS);
202 }
203
204 static int
205 dpdetach(dev_info_t *devi, ddi_detach_cmd_t cmd)
206 {
207 if (cmd != DDI_DETACH)
208 return (DDI_FAILURE);
209
210 ddi_remove_minor_node(devi, NULL);
211 return (DDI_SUCCESS);
212 }
213
214 /* ARGSUSED */
215 static int
216 dpinfo(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
217 {
218 int error;
219
220 switch (infocmd) {
221 case DDI_INFO_DEVT2DEVINFO:
222 *result = (void *)dpdevi;
223 error = DDI_SUCCESS;
224 break;
225 case DDI_INFO_DEVT2INSTANCE:
226 *result = (void *)0;
227 error = DDI_SUCCESS;
228 break;
229 default:
230 error = DDI_FAILURE;
231 }
232 return (error);
233 }
234
235 /*
236 * dp_pcache_poll has similar logic to pcache_poll() in poll.c. The major
237 * differences are: (1) /dev/poll requires scanning the bitmap starting at
238 * where it was stopped last time, instead of always starting from 0,
239 * (2) since user may not have cleaned up the cached fds when they are
240 * closed, some polldats in cache may refer to closed or reused fds. We
241 * need to check for those cases.
242 *
243 * NOTE: Upon closing an fd, automatic poll cache cleanup is done for
244 * poll(2) caches but NOT for /dev/poll caches. So expect some
245 * stale entries!
246 */
247 static int
248 dp_pcache_poll(dp_entry_t *dpep, void *dpbuf,
249 pollcache_t *pcp, nfds_t nfds, int *fdcntp)
250 {
251 int start, ostart, end;
252 int fdcnt, fd;
253 boolean_t done;
254 file_t *fp;
255 short revent;
256 boolean_t no_wrap;
257 pollhead_t *php;
258 polldat_t *pdp;
259 pollfd_t *pfdp;
260 epoll_event_t *epoll;
261 int error = 0;
262 short mask = POLLRDHUP | POLLWRBAND;
263 boolean_t is_epoll = (dpep->dpe_flag & DP_ISEPOLLCOMPAT) != 0;
264
265 ASSERT(MUTEX_HELD(&pcp->pc_lock));
266 if (pcp->pc_bitmap == NULL) {
267 /*
268 * No Need to search because no poll fd
269 * has been cached.
270 */
271 return (error);
272 }
273
274 if (is_epoll) {
275 pfdp = NULL;
276 epoll = (epoll_event_t *)dpbuf;
277 } else {
278 pfdp = (pollfd_t *)dpbuf;
279 epoll = NULL;
280 }
281 retry:
282 start = ostart = pcp->pc_mapstart;
283 end = pcp->pc_mapend;
284 php = NULL;
285
286 if (start == 0) {
287 /*
288 * started from every begining, no need to wrap around.
289 */
290 no_wrap = B_TRUE;
291 } else {
292 no_wrap = B_FALSE;
293 }
294 done = B_FALSE;
295 fdcnt = 0;
296 while ((fdcnt < nfds) && !done) {
297 php = NULL;
298 revent = 0;
299 /*
300 * Examine the bit map in a circular fashion
301 * to avoid starvation. Always resume from
302 * last stop. Scan till end of the map. Then
303 * wrap around.
304 */
305 fd = bt_getlowbit(pcp->pc_bitmap, start, end);
306 ASSERT(fd <= end);
307 if (fd >= 0) {
308 if (fd == end) {
309 if (no_wrap) {
310 done = B_TRUE;
311 } else {
312 start = 0;
313 end = ostart - 1;
314 no_wrap = B_TRUE;
315 }
316 } else {
317 start = fd + 1;
318 }
319 pdp = pcache_lookup_fd(pcp, fd);
320 repoll:
321 ASSERT(pdp != NULL);
322 ASSERT(pdp->pd_fd == fd);
323 if (pdp->pd_fp == NULL) {
324 /*
325 * The fd is POLLREMOVed. This fd is
326 * logically no longer cached. So move
327 * on to the next one.
328 */
329 continue;
330 }
331 if ((fp = getf(fd)) == NULL) {
332 /*
333 * The fd has been closed, but user has not
334 * done a POLLREMOVE on this fd yet. Instead
335 * of cleaning it here implicitly, we return
336 * POLLNVAL. This is consistent with poll(2)
337 * polling a closed fd. Hope this will remind
338 * user to do a POLLREMOVE.
339 */
340 if (!is_epoll && pfdp != NULL) {
341 pfdp[fdcnt].fd = fd;
342 pfdp[fdcnt].revents = POLLNVAL;
343 fdcnt++;
344 continue;
345 }
346
347 /*
348 * In the epoll compatibility case, we actually
349 * perform the implicit removal to remain
350 * closer to the epoll semantics.
351 */
352 if (is_epoll) {
353 pdp->pd_fp = NULL;
354 pdp->pd_events = 0;
355
356 if (php != NULL) {
357 pollhead_delete(php, pdp);
358 pdp->pd_php = NULL;
359 }
360
361 BT_CLEAR(pcp->pc_bitmap, fd);
362 continue;
363 }
364 }
365
366 if (fp != pdp->pd_fp) {
367 /*
368 * user is polling on a cached fd which was
369 * closed and then reused. Unfortunately
370 * there is no good way to inform user.
371 * If the file struct is also reused, we
372 * may not be able to detect the fd reuse
373 * at all. As long as this does not
374 * cause system failure and/or memory leak,
375 * we will play along. Man page states if
376 * user does not clean up closed fds, polling
377 * results will be indeterministic.
378 *
379 * XXX - perhaps log the detection of fd
380 * reuse?
381 */
382 pdp->pd_fp = fp;
383 }
384 /*
385 * XXX - pollrelock() logic needs to know which
386 * which pollcache lock to grab. It'd be a
387 * cleaner solution if we could pass pcp as
388 * an arguement in VOP_POLL interface instead
389 * of implicitly passing it using thread_t
390 * struct. On the other hand, changing VOP_POLL
391 * interface will require all driver/file system
392 * poll routine to change. May want to revisit
393 * the tradeoff later.
394 */
395 curthread->t_pollcache = pcp;
396 error = VOP_POLL(fp->f_vnode, pdp->pd_events, 0,
397 &revent, &php, NULL);
398 curthread->t_pollcache = NULL;
399 releasef(fd);
400 if (error != 0) {
401 break;
402 }
403
404 /*
405 * layered devices (e.g. console driver)
406 * may change the vnode and thus the pollhead
407 * pointer out from underneath us.
408 */
409 if (php != NULL && pdp->pd_php != NULL &&
410 php != pdp->pd_php) {
411 pollhead_delete(pdp->pd_php, pdp);
412 pdp->pd_php = php;
413 pollhead_insert(php, pdp);
414 /*
415 * The bit should still be set.
416 */
417 ASSERT(BT_TEST(pcp->pc_bitmap, fd));
418 goto retry;
419 }
420
421 if (revent != 0) {
422 if (pfdp != NULL) {
423 pfdp[fdcnt].fd = fd;
424 pfdp[fdcnt].events = pdp->pd_events;
425 pfdp[fdcnt].revents = revent;
426 } else if (epoll != NULL) {
427 epoll_event_t *ep = &epoll[fdcnt];
428
429 ASSERT(epoll != NULL);
430 ep->data.u64 = pdp->pd_epolldata;
431
432 /*
433 * If any of the event bits are set for
434 * which poll and epoll representations
435 * differ, swizzle in the native epoll
436 * values.
437 */
438 if (revent & mask) {
439 ep->events = (revent & ~mask) |
440 ((revent & POLLRDHUP) ?
441 EPOLLRDHUP : 0) |
442 ((revent & POLLWRBAND) ?
443 EPOLLWRBAND : 0);
444 } else {
445 ep->events = revent;
446 }
447
448 /*
449 * We define POLLWRNORM to be POLLOUT,
450 * but epoll has separate definitions
451 * for them; if POLLOUT is set and the
452 * user has asked for EPOLLWRNORM, set
453 * that as well.
454 */
455 if ((revent & POLLOUT) &&
456 (pdp->pd_events & EPOLLWRNORM)) {
457 ep->events |= EPOLLWRNORM;
458 }
459 } else {
460 pollstate_t *ps =
461 curthread->t_pollstate;
462 /*
463 * The devpoll handle itself is being
464 * polled. Notify the caller of any
465 * readable event(s), leaving as much
466 * state as possible untouched.
467 */
468 VERIFY(fdcnt == 0);
469 VERIFY(ps != NULL);
470
471 /*
472 * If a call to pollunlock() fails
473 * during VOP_POLL, skip over the fd
474 * and continue polling.
475 *
476 * Otherwise, report that there is an
477 * event pending.
478 */
479 if ((ps->ps_flags & POLLSTATE_ULFAIL)
480 != 0) {
481 ps->ps_flags &=
482 ~POLLSTATE_ULFAIL;
483 continue;
484 } else {
485 fdcnt++;
486 break;
487 }
488 }
489
490 /*
491 * If POLLET is set, clear the bit in the
492 * bitmap -- which effectively latches the
493 * edge on a pollwakeup() from the driver.
494 */
495 if (pdp->pd_events & POLLET)
496 BT_CLEAR(pcp->pc_bitmap, fd);
497
498 /*
499 * If POLLONESHOT is set, perform the implicit
500 * POLLREMOVE.
501 */
502 if (pdp->pd_events & POLLONESHOT) {
503 pdp->pd_fp = NULL;
504 pdp->pd_events = 0;
505
506 if (php != NULL) {
507 pollhead_delete(php, pdp);
508 pdp->pd_php = NULL;
509 }
510
511 BT_CLEAR(pcp->pc_bitmap, fd);
512 }
513
514 fdcnt++;
515 } else if (php != NULL) {
516 /*
517 * We clear a bit or cache a poll fd if
518 * the driver returns a poll head ptr,
519 * which is expected in the case of 0
520 * revents. Some buggy driver may return
521 * NULL php pointer with 0 revents. In
522 * this case, we just treat the driver as
523 * "noncachable" and not clearing the bit
524 * in bitmap.
525 */
526 if ((pdp->pd_php != NULL) &&
527 ((pcp->pc_flag & PC_POLLWAKE) == 0)) {
528 BT_CLEAR(pcp->pc_bitmap, fd);
529 }
530 if (pdp->pd_php == NULL) {
531 pollhead_insert(php, pdp);
532 pdp->pd_php = php;
533 /*
534 * An event of interest may have
535 * arrived between the VOP_POLL() and
536 * the pollhead_insert(); check again.
537 */
538 goto repoll;
539 }
540 }
541 } else {
542 /*
543 * No bit set in the range. Check for wrap around.
544 */
545 if (!no_wrap) {
546 start = 0;
547 end = ostart - 1;
548 no_wrap = B_TRUE;
549 } else {
550 done = B_TRUE;
551 }
552 }
553 }
554
555 if (!done) {
556 pcp->pc_mapstart = start;
557 }
558 ASSERT(*fdcntp == 0);
559 *fdcntp = fdcnt;
560 return (error);
561 }
562
563 /*ARGSUSED*/
564 static int
565 dpopen(dev_t *devp, int flag, int otyp, cred_t *credp)
566 {
567 minor_t minordev;
568 dp_entry_t *dpep;
569 pollcache_t *pcp;
570
571 ASSERT(devpoll_init);
572 ASSERT(dptblsize <= MAXMIN);
573 mutex_enter(&devpoll_lock);
574 for (minordev = 0; minordev < dptblsize; minordev++) {
575 if (devpolltbl[minordev] == NULL) {
576 devpolltbl[minordev] = (dp_entry_t *)RESERVED;
577 break;
578 }
579 }
580 if (minordev == dptblsize) {
581 dp_entry_t **newtbl;
582 size_t oldsize;
583
584 /*
585 * Used up every entry in the existing devpoll table.
586 * Grow the table by DEVPOLLSIZE.
587 */
588 if ((oldsize = dptblsize) >= MAXMIN) {
589 mutex_exit(&devpoll_lock);
590 return (ENXIO);
591 }
592 dptblsize += DEVPOLLSIZE;
593 if (dptblsize > MAXMIN) {
594 dptblsize = MAXMIN;
595 }
596 newtbl = kmem_zalloc(sizeof (caddr_t) * dptblsize, KM_SLEEP);
597 bcopy(devpolltbl, newtbl, sizeof (caddr_t) * oldsize);
598 kmem_free(devpolltbl, sizeof (caddr_t) * oldsize);
599 devpolltbl = newtbl;
600 devpolltbl[minordev] = (dp_entry_t *)RESERVED;
601 }
602 mutex_exit(&devpoll_lock);
603
604 dpep = kmem_zalloc(sizeof (dp_entry_t), KM_SLEEP);
605 /*
606 * allocate a pollcache skeleton here. Delay allocating bitmap
607 * structures until dpwrite() time, since we don't know the
608 * optimal size yet. We also delay setting the pid until either
609 * dpwrite() or attempt to poll on the instance, allowing parents
610 * to create instances of /dev/poll for their children. (In the
611 * epoll compatibility case, this check isn't performed to maintain
612 * semantic compatibility.)
613 */
614 pcp = pcache_alloc();
615 dpep->dpe_pcache = pcp;
616 pcp->pc_pid = -1;
617 *devp = makedevice(getmajor(*devp), minordev); /* clone the driver */
618 mutex_enter(&devpoll_lock);
619 ASSERT(minordev < dptblsize);
620 ASSERT(devpolltbl[minordev] == (dp_entry_t *)RESERVED);
621 devpolltbl[minordev] = dpep;
622 mutex_exit(&devpoll_lock);
623 return (0);
624 }
625
626 /*
627 * Write to dev/poll add/remove fd's to/from a cached poll fd set,
628 * or change poll events for a watched fd.
629 */
630 /*ARGSUSED*/
631 static int
632 dpwrite(dev_t dev, struct uio *uiop, cred_t *credp)
633 {
634 minor_t minor;
635 dp_entry_t *dpep;
636 pollcache_t *pcp;
637 pollfd_t *pollfdp, *pfdp;
638 dvpoll_epollfd_t *epfdp;
639 uintptr_t limit;
640 int error, size;
641 ssize_t uiosize;
642 nfds_t pollfdnum;
643 struct pollhead *php = NULL;
644 polldat_t *pdp;
645 int fd;
646 file_t *fp;
647 boolean_t is_epoll, fds_added = B_FALSE;
648
649 minor = getminor(dev);
650
651 mutex_enter(&devpoll_lock);
652 ASSERT(minor < dptblsize);
653 dpep = devpolltbl[minor];
654 ASSERT(dpep != NULL);
655 mutex_exit(&devpoll_lock);
656
657 mutex_enter(&dpep->dpe_lock);
658 pcp = dpep->dpe_pcache;
659 is_epoll = (dpep->dpe_flag & DP_ISEPOLLCOMPAT) != 0;
660 size = (is_epoll) ? sizeof (dvpoll_epollfd_t) : sizeof (pollfd_t);
661 mutex_exit(&dpep->dpe_lock);
662
663 if (!is_epoll && curproc->p_pid != pcp->pc_pid) {
664 if (pcp->pc_pid != -1) {
665 return (EACCES);
666 }
667
668 pcp->pc_pid = curproc->p_pid;
669 }
670
671 uiosize = uiop->uio_resid;
672 pollfdnum = uiosize / size;
673 mutex_enter(&curproc->p_lock);
674 if (pollfdnum > (uint_t)rctl_enforced_value(
675 rctlproc_legacy[RLIMIT_NOFILE], curproc->p_rctls, curproc)) {
676 (void) rctl_action(rctlproc_legacy[RLIMIT_NOFILE],
677 curproc->p_rctls, curproc, RCA_SAFE);
678 mutex_exit(&curproc->p_lock);
679 return (EINVAL);
680 }
681 mutex_exit(&curproc->p_lock);
682 /*
683 * Copy in the pollfd array. Walk through the array and add
684 * each polled fd to the cached set.
685 */
686 pollfdp = kmem_alloc(uiosize, KM_SLEEP);
687 limit = (uintptr_t)pollfdp + (pollfdnum * size);
688
689 /*
690 * Although /dev/poll uses the write(2) interface to cache fds, it's
691 * not supposed to function as a seekable device. To prevent offset
692 * from growing and eventually exceed the maximum, reset the offset
693 * here for every call.
694 */
695 uiop->uio_loffset = 0;
696 if ((error = uiomove((caddr_t)pollfdp, uiosize, UIO_WRITE, uiop))
697 != 0) {
698 kmem_free(pollfdp, uiosize);
699 return (error);
700 }
701 /*
702 * We are about to enter the core portion of dpwrite(). Make sure this
703 * write has exclusive access in this portion of the code, i.e., no
704 * other writers in this code.
705 *
706 * Waiting for all readers to drop their references to the dpe is
707 * unecessary since the pollcache itself is protected by pc_lock.
708 */
709 mutex_enter(&dpep->dpe_lock);
710 dpep->dpe_writerwait++;
711 while ((dpep->dpe_flag & DP_WRITER_PRESENT) != 0) {
712 ASSERT(dpep->dpe_refcnt != 0);
713
714 if (!cv_wait_sig_swap(&dpep->dpe_cv, &dpep->dpe_lock)) {
715 dpep->dpe_writerwait--;
716 mutex_exit(&dpep->dpe_lock);
717 kmem_free(pollfdp, uiosize);
718 return (EINTR);
719 }
720 }
721 dpep->dpe_writerwait--;
722 dpep->dpe_flag |= DP_WRITER_PRESENT;
723 dpep->dpe_refcnt++;
724
725 if (!is_epoll && (dpep->dpe_flag & DP_ISEPOLLCOMPAT) != 0) {
726 /*
727 * The epoll compat mode was enabled while we were waiting to
728 * establish write access. It is not safe to continue since
729 * state was prepared for non-epoll operation.
730 */
731 error = EBUSY;
732 goto bypass;
733 }
734 mutex_exit(&dpep->dpe_lock);
735
736 /*
737 * Since the dpwrite() may recursively walk an added /dev/poll handle,
738 * pollstate_enter() deadlock and loop detection must be used.
739 */
740 (void) pollstate_create();
741 VERIFY(pollstate_enter(pcp) == PSE_SUCCESS);
742
743 if (pcp->pc_bitmap == NULL) {
744 pcache_create(pcp, pollfdnum);
745 }
746 for (pfdp = pollfdp; (uintptr_t)pfdp < limit;
747 pfdp = (pollfd_t *)((uintptr_t)pfdp + size)) {
748 fd = pfdp->fd;
749 if ((uint_t)fd >= P_FINFO(curproc)->fi_nfiles) {
750 /*
751 * epoll semantics demand that we return EBADF if our
752 * specified fd is invalid.
753 */
754 if (is_epoll) {
755 error = EBADF;
756 break;
757 }
758
759 continue;
760 }
761
762 pdp = pcache_lookup_fd(pcp, fd);
763 if (pfdp->events != POLLREMOVE) {
764
765 fp = NULL;
766
767 if (pdp == NULL) {
768 /*
769 * If we're in epoll compatibility mode, check
770 * that the fd is valid before allocating
771 * anything for it; epoll semantics demand that
772 * we return EBADF if our specified fd is
773 * invalid.
774 */
775 if (is_epoll) {
776 if ((fp = getf(fd)) == NULL) {
777 error = EBADF;
778 break;
779 }
780 }
781
782 pdp = pcache_alloc_fd(0);
783 pdp->pd_fd = fd;
784 pdp->pd_pcache = pcp;
785 pcache_insert_fd(pcp, pdp, pollfdnum);
786 } else {
787 /*
788 * epoll semantics demand that we error out if
789 * a file descriptor is added twice, which we
790 * check (imperfectly) by checking if we both
791 * have the file descriptor cached and the
792 * file pointer that correponds to the file
793 * descriptor matches our cached value. If
794 * there is a pointer mismatch, the file
795 * descriptor was closed without being removed.
796 * The converse is clearly not true, however,
797 * so to narrow the window by which a spurious
798 * EEXIST may be returned, we also check if
799 * this fp has been added to an epoll control
800 * descriptor in the past; if it hasn't, we
801 * know that this is due to fp reuse -- it's
802 * not a true EEXIST case. (By performing this
803 * additional check, we limit the window of
804 * spurious EEXIST to situations where a single
805 * file descriptor is being used across two or
806 * more epoll control descriptors -- and even
807 * then, the file descriptor must be closed and
808 * reused in a relatively tight time span.)
809 */
810 if (is_epoll) {
811 if (pdp->pd_fp != NULL &&
812 (fp = getf(fd)) != NULL &&
813 fp == pdp->pd_fp &&
814 (fp->f_flag2 & FEPOLLED)) {
815 error = EEXIST;
816 releasef(fd);
817 break;
818 }
819
820 /*
821 * We have decided that the cached
822 * information was stale: it either
823 * didn't match, or the fp had never
824 * actually been epoll()'d on before.
825 * We need to now clear our pd_events
826 * to assure that we don't mistakenly
827 * operate on cached event disposition.
828 */
829 pdp->pd_events = 0;
830 }
831 }
832
833 if (is_epoll) {
834 epfdp = (dvpoll_epollfd_t *)pfdp;
835 pdp->pd_epolldata = epfdp->dpep_data;
836 }
837
838 ASSERT(pdp->pd_fd == fd);
839 ASSERT(pdp->pd_pcache == pcp);
840 if (fd >= pcp->pc_mapsize) {
841 mutex_exit(&pcp->pc_lock);
842 pcache_grow_map(pcp, fd);
843 mutex_enter(&pcp->pc_lock);
844 }
845 if (fd > pcp->pc_mapend) {
846 pcp->pc_mapend = fd;
847 }
848 if (fp == NULL && (fp = getf(fd)) == NULL) {
849 /*
850 * The fd is not valid. Since we can't pass
851 * this error back in the write() call, set
852 * the bit in bitmap to force DP_POLL ioctl
853 * to examine it.
854 */
855 BT_SET(pcp->pc_bitmap, fd);
856 pdp->pd_events |= pfdp->events;
857 continue;
858 }
859
860 /*
861 * To (greatly) reduce EEXIST false positives, we
862 * denote that this fp has been epoll()'d. We do this
863 * regardless of epoll compatibility mode, as the flag
864 * is harmless if not in epoll compatibility mode.
865 */
866 fp->f_flag2 |= FEPOLLED;
867
868 /*
869 * Don't do VOP_POLL for an already cached fd with
870 * same poll events.
871 */
872 if ((pdp->pd_events == pfdp->events) &&
873 (pdp->pd_fp == fp)) {
874 /*
875 * the events are already cached
876 */
877 releasef(fd);
878 continue;
879 }
880
881 /*
882 * do VOP_POLL and cache this poll fd.
883 */
884 /*
885 * XXX - pollrelock() logic needs to know which
886 * which pollcache lock to grab. It'd be a
887 * cleaner solution if we could pass pcp as
888 * an arguement in VOP_POLL interface instead
889 * of implicitly passing it using thread_t
890 * struct. On the other hand, changing VOP_POLL
891 * interface will require all driver/file system
892 * poll routine to change. May want to revisit
893 * the tradeoff later.
894 */
895 curthread->t_pollcache = pcp;
896 error = VOP_POLL(fp->f_vnode, pfdp->events, 0,
897 &pfdp->revents, &php, NULL);
898 curthread->t_pollcache = NULL;
899 /*
900 * We always set the bit when this fd is cached;
901 * this forces the first DP_POLL to poll this fd.
902 * Real performance gain comes from subsequent
903 * DP_POLL. We also attempt a pollhead_insert();
904 * if it's not possible, we'll do it in dpioctl().
905 */
906 BT_SET(pcp->pc_bitmap, fd);
907 if (error != 0) {
908 releasef(fd);
909 break;
910 }
911 pdp->pd_fp = fp;
912 pdp->pd_events |= pfdp->events;
913 if (php != NULL) {
914 if (pdp->pd_php == NULL) {
915 pollhead_insert(php, pdp);
916 pdp->pd_php = php;
917 } else {
918 if (pdp->pd_php != php) {
919 pollhead_delete(pdp->pd_php,
920 pdp);
921 pollhead_insert(php, pdp);
922 pdp->pd_php = php;
923 }
924 }
925 }
926 fds_added = B_TRUE;
927 releasef(fd);
928 } else {
929 if (pdp == NULL || pdp->pd_fp == NULL) {
930 if (is_epoll) {
931 /*
932 * As with the add case (above), epoll
933 * semantics demand that we error out
934 * in this case.
935 */
936 error = ENOENT;
937 break;
938 }
939
940 continue;
941 }
942 ASSERT(pdp->pd_fd == fd);
943 pdp->pd_fp = NULL;
944 pdp->pd_events = 0;
945 ASSERT(pdp->pd_thread == NULL);
946 if (pdp->pd_php != NULL) {
947 pollhead_delete(pdp->pd_php, pdp);
948 pdp->pd_php = NULL;
949 }
950 BT_CLEAR(pcp->pc_bitmap, fd);
951 }
952 }
953 /*
954 * Wake any pollcache waiters so they can check the new descriptors.
955 *
956 * Any fds added to an recursive-capable pollcache could themselves be
957 * /dev/poll handles. To ensure that proper event propagation occurs,
958 * parent pollcaches are woken too, so that they can create any needed
959 * pollcache links.
960 */
961 if (fds_added) {
962 cv_broadcast(&pcp->pc_cv);
963 pcache_wake_parents(pcp);
964 }
965 pollstate_exit(pcp);
966 mutex_enter(&dpep->dpe_lock);
967 bypass:
968 dpep->dpe_flag &= ~DP_WRITER_PRESENT;
969 dpep->dpe_refcnt--;
970 cv_broadcast(&dpep->dpe_cv);
971 mutex_exit(&dpep->dpe_lock);
972 kmem_free(pollfdp, uiosize);
973 return (error);
974 }
975
976 #define DP_SIGMASK_RESTORE(ksetp) { \
977 if (ksetp != NULL) { \
978 mutex_enter(&p->p_lock); \
979 if (lwp->lwp_cursig == 0) { \
980 t->t_hold = lwp->lwp_sigoldmask; \
981 t->t_flag &= ~T_TOMASK; \
982 } \
983 mutex_exit(&p->p_lock); \
984 } \
985 }
986
987 /*ARGSUSED*/
988 static int
989 dpioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp, int *rvalp)
990 {
991 minor_t minor;
992 dp_entry_t *dpep;
993 pollcache_t *pcp;
994 hrtime_t now;
995 int error = 0;
996 boolean_t is_epoll;
997 STRUCT_DECL(dvpoll, dvpoll);
998
999 if (cmd == DP_POLL || cmd == DP_PPOLL) {
1000 /* do this now, before we sleep on DP_WRITER_PRESENT */
1001 now = gethrtime();
1002 }
1003
1004 minor = getminor(dev);
1005 mutex_enter(&devpoll_lock);
1006 ASSERT(minor < dptblsize);
1007 dpep = devpolltbl[minor];
1008 mutex_exit(&devpoll_lock);
1009 ASSERT(dpep != NULL);
1010 pcp = dpep->dpe_pcache;
1011
1012 mutex_enter(&dpep->dpe_lock);
1013 is_epoll = (dpep->dpe_flag & DP_ISEPOLLCOMPAT) != 0;
1014
1015 if (cmd == DP_EPOLLCOMPAT) {
1016 if (dpep->dpe_refcnt != 0) {
1017 /*
1018 * We can't turn on epoll compatibility while there
1019 * are outstanding operations.
1020 */
1021 mutex_exit(&dpep->dpe_lock);
1022 return (EBUSY);
1023 }
1024
1025 /*
1026 * epoll compatibility is a one-way street: there's no way
1027 * to turn it off for a particular open.
1028 */
1029 dpep->dpe_flag |= DP_ISEPOLLCOMPAT;
1030 mutex_exit(&dpep->dpe_lock);
1031
1032 return (0);
1033 }
1034
1035 if (!is_epoll && curproc->p_pid != pcp->pc_pid) {
1036 if (pcp->pc_pid != -1) {
1037 mutex_exit(&dpep->dpe_lock);
1038 return (EACCES);
1039 }
1040
1041 pcp->pc_pid = curproc->p_pid;
1042 }
1043
1044 /* Wait until all writers have cleared the handle before continuing */
1045 while ((dpep->dpe_flag & DP_WRITER_PRESENT) != 0 ||
1046 (dpep->dpe_writerwait != 0)) {
1047 if (!cv_wait_sig_swap(&dpep->dpe_cv, &dpep->dpe_lock)) {
1048 mutex_exit(&dpep->dpe_lock);
1049 return (EINTR);
1050 }
1051 }
1052 dpep->dpe_refcnt++;
1053 mutex_exit(&dpep->dpe_lock);
1054
1055 switch (cmd) {
1056 case DP_POLL:
1057 case DP_PPOLL:
1058 {
1059 pollstate_t *ps;
1060 nfds_t nfds;
1061 int fdcnt = 0;
1062 size_t size, fdsize, dpsize;
1063 hrtime_t deadline = 0;
1064 k_sigset_t *ksetp = NULL;
1065 k_sigset_t kset;
1066 sigset_t set;
1067 kthread_t *t = curthread;
1068 klwp_t *lwp = ttolwp(t);
1069 struct proc *p = ttoproc(curthread);
1070
1071 STRUCT_INIT(dvpoll, mode);
1072
1073 /*
1074 * The dp_setp member is only required/consumed for DP_PPOLL,
1075 * which otherwise uses the same structure as DP_POLL.
1076 */
1077 if (cmd == DP_POLL) {
1078 dpsize = (uintptr_t)STRUCT_FADDR(dvpoll, dp_setp) -
1079 (uintptr_t)STRUCT_FADDR(dvpoll, dp_fds);
1080 } else {
1081 ASSERT(cmd == DP_PPOLL);
1082 dpsize = STRUCT_SIZE(dvpoll);
1083 }
1084
1085 if ((mode & FKIOCTL) != 0) {
1086 /* Kernel-internal ioctl call */
1087 bcopy((caddr_t)arg, STRUCT_BUF(dvpoll), dpsize);
1088 error = 0;
1089 } else {
1090 error = copyin((caddr_t)arg, STRUCT_BUF(dvpoll),
1091 dpsize);
1092 }
1093
1094 if (error) {
1095 DP_REFRELE(dpep);
1096 return (EFAULT);
1097 }
1098
1099 deadline = STRUCT_FGET(dvpoll, dp_timeout);
1100 if (deadline > 0) {
1101 /*
1102 * Convert the deadline from relative milliseconds
1103 * to absolute nanoseconds. They must wait for at
1104 * least a tick.
1105 */
1106 deadline = MSEC2NSEC(deadline);
1107 deadline = MAX(deadline, nsec_per_tick);
1108 deadline += now;
1109 }
1110
1111 if (cmd == DP_PPOLL) {
1112 void *setp = STRUCT_FGETP(dvpoll, dp_setp);
1113
1114 if (setp != NULL) {
1115 if (copyin(setp, &set, sizeof (set))) {
1116 DP_REFRELE(dpep);
1117 return (EFAULT);
1118 }
1119
1120 sigutok(&set, &kset);
1121 ksetp = &kset;
1122
1123 mutex_enter(&p->p_lock);
1124 schedctl_finish_sigblock(t);
1125 lwp->lwp_sigoldmask = t->t_hold;
1126 t->t_hold = *ksetp;
1127 t->t_flag |= T_TOMASK;
1128
1129 /*
1130 * Like ppoll() with a non-NULL sigset, we'll
1131 * call cv_reltimedwait_sig() just to check for
1132 * signals. This call will return immediately
1133 * with either 0 (signalled) or -1 (no signal).
1134 * There are some conditions whereby we can
1135 * get 0 from cv_reltimedwait_sig() without
1136 * a true signal (e.g., a directed stop), so
1137 * we restore our signal mask in the unlikely
1138 * event that lwp_cursig is 0.
1139 */
1140 if (!cv_reltimedwait_sig(&t->t_delay_cv,
1141 &p->p_lock, 0, TR_CLOCK_TICK)) {
1142 if (lwp->lwp_cursig == 0) {
1143 t->t_hold = lwp->lwp_sigoldmask;
1144 t->t_flag &= ~T_TOMASK;
1145 }
1146
1147 mutex_exit(&p->p_lock);
1148
1149 DP_REFRELE(dpep);
1150 return (EINTR);
1151 }
1152
1153 mutex_exit(&p->p_lock);
1154 }
1155 }
1156
1157 if ((nfds = STRUCT_FGET(dvpoll, dp_nfds)) == 0) {
1158 /*
1159 * We are just using DP_POLL to sleep, so
1160 * we don't any of the devpoll apparatus.
1161 * Do not check for signals if we have a zero timeout.
1162 */
1163 DP_REFRELE(dpep);
1164 if (deadline == 0) {
1165 DP_SIGMASK_RESTORE(ksetp);
1166 return (0);
1167 }
1168
1169 mutex_enter(&curthread->t_delay_lock);
1170 while ((error =
1171 cv_timedwait_sig_hrtime(&curthread->t_delay_cv,
1172 &curthread->t_delay_lock, deadline)) > 0)
1173 continue;
1174 mutex_exit(&curthread->t_delay_lock);
1175
1176 DP_SIGMASK_RESTORE(ksetp);
1177
1178 return (error == 0 ? EINTR : 0);
1179 }
1180
1181 if (is_epoll) {
1182 size = nfds * (fdsize = sizeof (epoll_event_t));
1183 } else {
1184 size = nfds * (fdsize = sizeof (pollfd_t));
1185 }
1186
1187 /*
1188 * XXX It would be nice not to have to alloc each time, but it
1189 * requires another per thread structure hook. This can be
1190 * implemented later if data suggests that it's necessary.
1191 */
1192 ps = pollstate_create();
1193
1194 if (ps->ps_dpbufsize < size) {
1195 /*
1196 * If nfds is larger than twice the current maximum
1197 * open file count, we'll silently clamp it. This
1198 * only limits our exposure to allocating an
1199 * inordinate amount of kernel memory; it doesn't
1200 * otherwise affect the semantics. (We have this
1201 * check at twice the maximum instead of merely the
1202 * maximum because some applications pass an nfds that
1203 * is only slightly larger than their limit.)
1204 */
1205 mutex_enter(&p->p_lock);
1206 if ((nfds >> 1) > p->p_fno_ctl) {
1207 nfds = p->p_fno_ctl;
1208 size = nfds * fdsize;
1209 }
1210 mutex_exit(&p->p_lock);
1211
1212 if (ps->ps_dpbufsize < size) {
1213 kmem_free(ps->ps_dpbuf, ps->ps_dpbufsize);
1214 ps->ps_dpbuf = kmem_zalloc(size, KM_SLEEP);
1215 ps->ps_dpbufsize = size;
1216 }
1217 }
1218
1219 VERIFY(pollstate_enter(pcp) == PSE_SUCCESS);
1220 for (;;) {
1221 pcp->pc_flag &= ~PC_POLLWAKE;
1222
1223 /*
1224 * Mark all child pcachelinks as stale.
1225 * Those which are still part of the tree will be
1226 * marked as valid during the poll.
1227 */
1228 pcachelink_mark_stale(pcp);
1229
1230 error = dp_pcache_poll(dpep, ps->ps_dpbuf,
1231 pcp, nfds, &fdcnt);
1232 if (fdcnt > 0 || error != 0)
1233 break;
1234
1235 /* Purge still-stale child pcachelinks */
1236 pcachelink_purge_stale(pcp);
1237
1238 /*
1239 * A pollwake has happened since we polled cache.
1240 */
1241 if (pcp->pc_flag & PC_POLLWAKE)
1242 continue;
1243
1244 /*
1245 * Sleep until we are notified, signaled, or timed out.
1246 */
1247 if (deadline == 0) {
1248 /* immediate timeout; do not check signals */
1249 break;
1250 }
1251
1252 error = cv_timedwait_sig_hrtime(&pcp->pc_cv,
1253 &pcp->pc_lock, deadline);
1254
1255 /*
1256 * If we were awakened by a signal or timeout then
1257 * break the loop, else poll again.
1258 */
1259 if (error <= 0) {
1260 error = (error == 0) ? EINTR : 0;
1261 break;
1262 } else {
1263 error = 0;
1264 }
1265 }
1266 pollstate_exit(pcp);
1267
1268 DP_SIGMASK_RESTORE(ksetp);
1269
1270 if (error == 0 && fdcnt > 0) {
1271 if (copyout(ps->ps_dpbuf,
1272 STRUCT_FGETP(dvpoll, dp_fds), fdcnt * fdsize)) {
1273 DP_REFRELE(dpep);
1274 return (EFAULT);
1275 }
1276 *rvalp = fdcnt;
1277 }
1278 break;
1279 }
1280
1281 case DP_ISPOLLED:
1282 {
1283 pollfd_t pollfd;
1284 polldat_t *pdp;
1285
1286 STRUCT_INIT(dvpoll, mode);
1287 error = copyin((caddr_t)arg, &pollfd, sizeof (pollfd_t));
1288 if (error) {
1289 DP_REFRELE(dpep);
1290 return (EFAULT);
1291 }
1292 mutex_enter(&pcp->pc_lock);
1293 if (pcp->pc_hash == NULL) {
1294 /*
1295 * No Need to search because no poll fd
1296 * has been cached.
1297 */
1298 mutex_exit(&pcp->pc_lock);
1299 DP_REFRELE(dpep);
1300 return (0);
1301 }
1302 if (pollfd.fd < 0) {
1303 mutex_exit(&pcp->pc_lock);
1304 break;
1305 }
1306 pdp = pcache_lookup_fd(pcp, pollfd.fd);
1307 if ((pdp != NULL) && (pdp->pd_fd == pollfd.fd) &&
1308 (pdp->pd_fp != NULL)) {
1309 pollfd.revents = pdp->pd_events;
1310 if (copyout(&pollfd, (caddr_t)arg, sizeof (pollfd_t))) {
1311 mutex_exit(&pcp->pc_lock);
1312 DP_REFRELE(dpep);
1313 return (EFAULT);
1314 }
1315 *rvalp = 1;
1316 }
1317 mutex_exit(&pcp->pc_lock);
1318 break;
1319 }
1320
1321 default:
1322 DP_REFRELE(dpep);
1323 return (EINVAL);
1324 }
1325 DP_REFRELE(dpep);
1326 return (error);
1327 }
1328
1329 /*
1330 * Overview of Recursive Polling
1331 *
1332 * It is possible for /dev/poll to poll for events on file descriptors which
1333 * themselves are /dev/poll handles. Pending events in the child handle are
1334 * represented as readable data via the POLLIN flag. To limit surface area,
1335 * this recursion is presently allowed on only /dev/poll handles which have
1336 * been placed in epoll mode via the DP_EPOLLCOMPAT ioctl. Recursion depth is
1337 * limited to 5 in order to be consistent with Linux epoll.
1338 *
1339 * Extending dppoll() for VOP_POLL:
1340 *
1341 * The recursive /dev/poll implementation begins by extending dppoll() to
1342 * report when resources contained in the pollcache have relevant event state.
1343 * At the highest level, it means calling dp_pcache_poll() so it indicates if
1344 * fd events are present without consuming them or altering the pollcache
1345 * bitmap. This ensures that a subsequent DP_POLL operation on the bitmap will
1346 * yield the initiating event. Additionally, the VOP_POLL should return in
1347 * such a way that dp_pcache_poll() does not clear the parent bitmap entry
1348 * which corresponds to the child /dev/poll fd. This means that child
1349 * pollcaches will be checked during every poll which facilitates wake-up
1350 * behavior detailed below.
1351 *
1352 * Pollcache Links and Wake Events:
1353 *
1354 * Recursive /dev/poll avoids complicated pollcache locking constraints during
1355 * pollwakeup events by eschewing the traditional pollhead mechanism in favor
1356 * of a different approach. For each pollcache at the root of a recursive
1357 * /dev/poll "tree", pcachelink_t structures are established to all child
1358 * /dev/poll pollcaches. During pollnotify() in a child pollcache, the
1359 * linked list of pcachelink_t entries is walked, where those marked as valid
1360 * incur a cv_broadcast to their parent pollcache. Most notably, these
1361 * pcachelink_t cv wakeups are performed without acquiring pc_lock on the
1362 * parent pollcache (which would require careful deadlock avoidance). This
1363 * still allows the woken poll on the parent to discover the pertinent events
1364 * due to the fact that bitmap entires for the child pollcache are always
1365 * maintained by the dppoll() logic above.
1366 *
1367 * Depth Limiting and Loop Prevention:
1368 *
1369 * As each pollcache is encountered (either via DP_POLL or dppoll()), depth and
1370 * loop constraints are enforced via pollstate_enter(). The pollcache_t
1371 * pointer is compared against any existing entries in ps_pc_stack and is added
1372 * to the end if no match (and therefore loop) is found. Once poll operations
1373 * for a given pollcache_t are complete, pollstate_exit() clears the pointer
1374 * from the list. The pollstate_enter() and pollstate_exit() functions are
1375 * responsible for acquiring and releasing pc_lock, respectively.
1376 *
1377 * Deadlock Safety:
1378 *
1379 * Descending through a tree of recursive /dev/poll handles involves the tricky
1380 * business of sequentially entering multiple pollcache locks. This tree
1381 * topology cannot define a lock acquisition order in such a way that it is
1382 * immune to deadlocks between threads. The pollstate_enter() and
1383 * pollstate_exit() functions provide an interface for recursive /dev/poll
1384 * operations to safely lock pollcaches while failing gracefully in the face of
1385 * deadlocking topologies. (See pollstate_contend() for more detail about how
1386 * deadlocks are detected and resolved.)
1387 */
1388
1389 /*ARGSUSED*/
1390 static int
1391 dppoll(dev_t dev, short events, int anyyet, short *reventsp,
1392 struct pollhead **phpp)
1393 {
1394 minor_t minor;
1395 dp_entry_t *dpep;
1396 pollcache_t *pcp;
1397 int res, rc = 0;
1398
1399 minor = getminor(dev);
1400 mutex_enter(&devpoll_lock);
1401 ASSERT(minor < dptblsize);
1402 dpep = devpolltbl[minor];
1403 ASSERT(dpep != NULL);
1404 mutex_exit(&devpoll_lock);
1405
1406 mutex_enter(&dpep->dpe_lock);
1407 if ((dpep->dpe_flag & DP_ISEPOLLCOMPAT) == 0) {
1408 /* Poll recursion is not yet supported for non-epoll handles */
1409 *reventsp = POLLERR;
1410 mutex_exit(&dpep->dpe_lock);
1411 return (0);
1412 } else {
1413 dpep->dpe_refcnt++;
1414 pcp = dpep->dpe_pcache;
1415 mutex_exit(&dpep->dpe_lock);
1416 }
1417
1418 res = pollstate_enter(pcp);
1419 if (res == PSE_SUCCESS) {
1420 nfds_t nfds = 1;
1421 int fdcnt = 0;
1422 pollstate_t *ps = curthread->t_pollstate;
1423
1424 rc = dp_pcache_poll(dpep, NULL, pcp, nfds, &fdcnt);
1425 if (rc == 0) {
1426 *reventsp = (fdcnt > 0) ? POLLIN : 0;
1427 }
1428 pcachelink_assoc(pcp, ps->ps_pc_stack[0]);
1429 pollstate_exit(pcp);
1430 } else {
1431 switch (res) {
1432 case PSE_FAIL_DEPTH:
1433 rc = EINVAL;
1434 break;
1435 case PSE_FAIL_LOOP:
1436 case PSE_FAIL_DEADLOCK:
1437 rc = ELOOP;
1438 break;
1439 default:
1440 /*
1441 * If anything else has gone awry, such as being polled
1442 * from an unexpected context, fall back to the
1443 * recursion-intolerant response.
1444 */
1445 *reventsp = POLLERR;
1446 rc = 0;
1447 break;
1448 }
1449 }
1450
1451 DP_REFRELE(dpep);
1452 return (rc);
1453 }
1454
1455 /*
1456 * devpoll close should do enough clean up before the pollcache is deleted,
1457 * i.e., it should ensure no one still references the pollcache later.
1458 * There is no "permission" check in here. Any process having the last
1459 * reference of this /dev/poll fd can close.
1460 */
1461 /*ARGSUSED*/
1462 static int
1463 dpclose(dev_t dev, int flag, int otyp, cred_t *credp)
1464 {
1465 minor_t minor;
1466 dp_entry_t *dpep;
1467 pollcache_t *pcp;
1468 int i;
1469 polldat_t **hashtbl;
1470 polldat_t *pdp;
1471
1472 minor = getminor(dev);
1473
1474 mutex_enter(&devpoll_lock);
1475 dpep = devpolltbl[minor];
1476 ASSERT(dpep != NULL);
1477 devpolltbl[minor] = NULL;
1478 mutex_exit(&devpoll_lock);
1479 pcp = dpep->dpe_pcache;
1480 ASSERT(pcp != NULL);
1481 /*
1482 * At this point, no other lwp can access this pollcache via the
1483 * /dev/poll fd. This pollcache is going away, so do the clean
1484 * up without the pc_lock.
1485 */
1486 hashtbl = pcp->pc_hash;
1487 for (i = 0; i < pcp->pc_hashsize; i++) {
1488 for (pdp = hashtbl[i]; pdp; pdp = pdp->pd_hashnext) {
1489 if (pdp->pd_php != NULL) {
1490 pollhead_delete(pdp->pd_php, pdp);
1491 pdp->pd_php = NULL;
1492 pdp->pd_fp = NULL;
1493 }
1494 }
1495 }
1496 /*
1497 * pollwakeup() may still interact with this pollcache. Wait until
1498 * it is done.
1499 */
1500 mutex_enter(&pcp->pc_no_exit);
1501 ASSERT(pcp->pc_busy >= 0);
1502 while (pcp->pc_busy > 0)
1503 cv_wait(&pcp->pc_busy_cv, &pcp->pc_no_exit);
1504 mutex_exit(&pcp->pc_no_exit);
1505
1506 /* Clean up any pollcache links created via recursive /dev/poll */
1507 if (pcp->pc_parents != NULL || pcp->pc_children != NULL) {
1508 /*
1509 * Because of the locking rules for pcachelink manipulation,
1510 * acquring pc_lock is required for this step.
1511 */
1512 mutex_enter(&pcp->pc_lock);
1513 pcachelink_purge_all(pcp);
1514 mutex_exit(&pcp->pc_lock);
1515 }
1516
1517 pcache_destroy(pcp);
1518 ASSERT(dpep->dpe_refcnt == 0);
1519 kmem_free(dpep, sizeof (dp_entry_t));
1520 return (0);
1521 }
1522
1523 static void
1524 pcachelink_locked_rele(pcachelink_t *pl)
1525 {
1526 ASSERT(MUTEX_HELD(&pl->pcl_lock));
1527 VERIFY(pl->pcl_refcnt >= 1);
1528
1529 pl->pcl_refcnt--;
1530 if (pl->pcl_refcnt == 0) {
1531 VERIFY(pl->pcl_state == PCL_INVALID);
1532 ASSERT(pl->pcl_parent_pc == NULL);
1533 ASSERT(pl->pcl_child_pc == NULL);
1534 ASSERT(pl->pcl_parent_next == NULL);
1535 ASSERT(pl->pcl_child_next == NULL);
1536
1537 pl->pcl_state = PCL_FREE;
1538 mutex_destroy(&pl->pcl_lock);
1539 kmem_free(pl, sizeof (pcachelink_t));
1540 } else {
1541 mutex_exit(&pl->pcl_lock);
1542 }
1543 }
1544
1545 /*
1546 * Associate parent and child pollcaches via a pcachelink_t. If an existing
1547 * link (stale or valid) between the two is found, it will be reused. If a
1548 * suitable link is not found for reuse, a new one will be allocated.
1549 */
1550 static void
1551 pcachelink_assoc(pollcache_t *child, pollcache_t *parent)
1552 {
1553 pcachelink_t *pl, **plpn;
1554
1555 ASSERT(MUTEX_HELD(&child->pc_lock));
1556 ASSERT(MUTEX_HELD(&parent->pc_lock));
1557
1558 /* Search for an existing link we can reuse. */
1559 plpn = &child->pc_parents;
1560 for (pl = child->pc_parents; pl != NULL; pl = *plpn) {
1561 mutex_enter(&pl->pcl_lock);
1562 if (pl->pcl_state == PCL_INVALID) {
1563 /* Clean any invalid links while walking the list */
1564 *plpn = pl->pcl_parent_next;
1565 pl->pcl_child_pc = NULL;
1566 pl->pcl_parent_next = NULL;
1567 pcachelink_locked_rele(pl);
1568 } else if (pl->pcl_parent_pc == parent) {
1569 /* Successfully found parent link */
1570 ASSERT(pl->pcl_state == PCL_VALID ||
1571 pl->pcl_state == PCL_STALE);
1572 pl->pcl_state = PCL_VALID;
1573 mutex_exit(&pl->pcl_lock);
1574 return;
1575 } else {
1576 plpn = &pl->pcl_parent_next;
1577 mutex_exit(&pl->pcl_lock);
1578 }
1579 }
1580
1581 /* No existing link to the parent was found. Create a fresh one. */
1582 pl = kmem_zalloc(sizeof (pcachelink_t), KM_SLEEP);
1583 mutex_init(&pl->pcl_lock, NULL, MUTEX_DEFAULT, NULL);
1584
1585 pl->pcl_parent_pc = parent;
1586 pl->pcl_child_next = parent->pc_children;
1587 parent->pc_children = pl;
1588 pl->pcl_refcnt++;
1589
1590 pl->pcl_child_pc = child;
1591 pl->pcl_parent_next = child->pc_parents;
1592 child->pc_parents = pl;
1593 pl->pcl_refcnt++;
1594
1595 pl->pcl_state = PCL_VALID;
1596 }
1597
1598 /*
1599 * Mark all child links in a pollcache as stale. Any invalid child links found
1600 * during iteration are purged.
1601 */
1602 static void
1603 pcachelink_mark_stale(pollcache_t *pcp)
1604 {
1605 pcachelink_t *pl, **plpn;
1606
1607 ASSERT(MUTEX_HELD(&pcp->pc_lock));
1608
1609 plpn = &pcp->pc_children;
1610 for (pl = pcp->pc_children; pl != NULL; pl = *plpn) {
1611 mutex_enter(&pl->pcl_lock);
1612 if (pl->pcl_state == PCL_INVALID) {
1613 /*
1614 * Remove any invalid links while we are going to the
1615 * trouble of walking the list.
1616 */
1617 *plpn = pl->pcl_child_next;
1618 pl->pcl_parent_pc = NULL;
1619 pl->pcl_child_next = NULL;
1620 pcachelink_locked_rele(pl);
1621 } else {
1622 pl->pcl_state = PCL_STALE;
1623 plpn = &pl->pcl_child_next;
1624 mutex_exit(&pl->pcl_lock);
1625 }
1626 }
1627 }
1628
1629 /*
1630 * Purge all stale (or invalid) child links from a pollcache.
1631 */
1632 static void
1633 pcachelink_purge_stale(pollcache_t *pcp)
1634 {
1635 pcachelink_t *pl, **plpn;
1636
1637 ASSERT(MUTEX_HELD(&pcp->pc_lock));
1638
1639 plpn = &pcp->pc_children;
1640 for (pl = pcp->pc_children; pl != NULL; pl = *plpn) {
1641 mutex_enter(&pl->pcl_lock);
1642 switch (pl->pcl_state) {
1643 case PCL_STALE:
1644 pl->pcl_state = PCL_INVALID;
1645 /* FALLTHROUGH */
1646 case PCL_INVALID:
1647 *plpn = pl->pcl_child_next;
1648 pl->pcl_parent_pc = NULL;
1649 pl->pcl_child_next = NULL;
1650 pcachelink_locked_rele(pl);
1651 break;
1652 default:
1653 plpn = &pl->pcl_child_next;
1654 mutex_exit(&pl->pcl_lock);
1655 }
1656 }
1657 }
1658
1659 /*
1660 * Purge all child and parent links from a pollcache, regardless of status.
1661 */
1662 static void
1663 pcachelink_purge_all(pollcache_t *pcp)
1664 {
1665 pcachelink_t *pl, **plpn;
1666
1667 ASSERT(MUTEX_HELD(&pcp->pc_lock));
1668
1669 plpn = &pcp->pc_parents;
1670 for (pl = pcp->pc_parents; pl != NULL; pl = *plpn) {
1671 mutex_enter(&pl->pcl_lock);
1672 pl->pcl_state = PCL_INVALID;
1673 *plpn = pl->pcl_parent_next;
1674 pl->pcl_child_pc = NULL;
1675 pl->pcl_parent_next = NULL;
1676 pcachelink_locked_rele(pl);
1677 }
1678
1679 plpn = &pcp->pc_children;
1680 for (pl = pcp->pc_children; pl != NULL; pl = *plpn) {
1681 mutex_enter(&pl->pcl_lock);
1682 pl->pcl_state = PCL_INVALID;
1683 *plpn = pl->pcl_child_next;
1684 pl->pcl_parent_pc = NULL;
1685 pl->pcl_child_next = NULL;
1686 pcachelink_locked_rele(pl);
1687 }
1688
1689 ASSERT(pcp->pc_parents == NULL);
1690 ASSERT(pcp->pc_children == NULL);
1691 }