FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_alq.c
1 /*-
2 * Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
3 * Copyright (c) 2008-2009, Lawrence Stewart <lstewart@freebsd.org>
4 * Copyright (c) 2009-2010, The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * Portions of this software were developed at the Centre for Advanced
8 * Internet Architectures, Swinburne University of Technology, Melbourne,
9 * Australia by Lawrence Stewart under sponsorship from the FreeBSD Foundation.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice unmodified, this list of conditions, and the following
16 * disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD: releng/10.0/sys/kern/kern_alq.c 251838 2013-06-17 09:49:07Z lstewart $");
35
36 #include "opt_mac.h"
37
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/kernel.h>
41 #include <sys/kthread.h>
42 #include <sys/lock.h>
43 #include <sys/mount.h>
44 #include <sys/mutex.h>
45 #include <sys/namei.h>
46 #include <sys/proc.h>
47 #include <sys/vnode.h>
48 #include <sys/alq.h>
49 #include <sys/malloc.h>
50 #include <sys/unistd.h>
51 #include <sys/fcntl.h>
52 #include <sys/eventhandler.h>
53
54 #include <security/mac/mac_framework.h>
55
56 /* Async. Logging Queue */
57 struct alq {
58 char *aq_entbuf; /* Buffer for stored entries */
59 int aq_entmax; /* Max entries */
60 int aq_entlen; /* Entry length */
61 int aq_freebytes; /* Bytes available in buffer */
62 int aq_buflen; /* Total length of our buffer */
63 int aq_writehead; /* Location for next write */
64 int aq_writetail; /* Flush starts at this location */
65 int aq_wrapearly; /* # bytes left blank at end of buf */
66 int aq_flags; /* Queue flags */
67 int aq_waiters; /* Num threads waiting for resources
68 * NB: Used as a wait channel so must
69 * not be first field in the alq struct
70 */
71 struct ale aq_getpost; /* ALE for use by get/post */
72 struct mtx aq_mtx; /* Queue lock */
73 struct vnode *aq_vp; /* Open vnode handle */
74 struct ucred *aq_cred; /* Credentials of the opening thread */
75 LIST_ENTRY(alq) aq_act; /* List of active queues */
76 LIST_ENTRY(alq) aq_link; /* List of all queues */
77 };
78
79 #define AQ_WANTED 0x0001 /* Wakeup sleeper when io is done */
80 #define AQ_ACTIVE 0x0002 /* on the active list */
81 #define AQ_FLUSHING 0x0004 /* doing IO */
82 #define AQ_SHUTDOWN 0x0008 /* Queue no longer valid */
83 #define AQ_ORDERED 0x0010 /* Queue enforces ordered writes */
84 #define AQ_LEGACY 0x0020 /* Legacy queue (fixed length writes) */
85
86 #define ALQ_LOCK(alq) mtx_lock_spin(&(alq)->aq_mtx)
87 #define ALQ_UNLOCK(alq) mtx_unlock_spin(&(alq)->aq_mtx)
88
89 #define HAS_PENDING_DATA(alq) ((alq)->aq_freebytes != (alq)->aq_buflen)
90
91 static MALLOC_DEFINE(M_ALD, "ALD", "ALD");
92
93 /*
94 * The ald_mtx protects the ald_queues list and the ald_active list.
95 */
96 static struct mtx ald_mtx;
97 static LIST_HEAD(, alq) ald_queues;
98 static LIST_HEAD(, alq) ald_active;
99 static int ald_shutingdown = 0;
100 struct thread *ald_thread;
101 static struct proc *ald_proc;
102 static eventhandler_tag alq_eventhandler_tag = NULL;
103
104 #define ALD_LOCK() mtx_lock(&ald_mtx)
105 #define ALD_UNLOCK() mtx_unlock(&ald_mtx)
106
107 /* Daemon functions */
108 static int ald_add(struct alq *);
109 static int ald_rem(struct alq *);
110 static void ald_startup(void *);
111 static void ald_daemon(void);
112 static void ald_shutdown(void *, int);
113 static void ald_activate(struct alq *);
114 static void ald_deactivate(struct alq *);
115
116 /* Internal queue functions */
117 static void alq_shutdown(struct alq *);
118 static void alq_destroy(struct alq *);
119 static int alq_doio(struct alq *);
120
121
122 /*
123 * Add a new queue to the global list. Fail if we're shutting down.
124 */
125 static int
126 ald_add(struct alq *alq)
127 {
128 int error;
129
130 error = 0;
131
132 ALD_LOCK();
133 if (ald_shutingdown) {
134 error = EBUSY;
135 goto done;
136 }
137 LIST_INSERT_HEAD(&ald_queues, alq, aq_link);
138 done:
139 ALD_UNLOCK();
140 return (error);
141 }
142
143 /*
144 * Remove a queue from the global list unless we're shutting down. If so,
145 * the ald will take care of cleaning up it's resources.
146 */
147 static int
148 ald_rem(struct alq *alq)
149 {
150 int error;
151
152 error = 0;
153
154 ALD_LOCK();
155 if (ald_shutingdown) {
156 error = EBUSY;
157 goto done;
158 }
159 LIST_REMOVE(alq, aq_link);
160 done:
161 ALD_UNLOCK();
162 return (error);
163 }
164
165 /*
166 * Put a queue on the active list. This will schedule it for writing.
167 */
168 static void
169 ald_activate(struct alq *alq)
170 {
171 LIST_INSERT_HEAD(&ald_active, alq, aq_act);
172 wakeup(&ald_active);
173 }
174
175 static void
176 ald_deactivate(struct alq *alq)
177 {
178 LIST_REMOVE(alq, aq_act);
179 alq->aq_flags &= ~AQ_ACTIVE;
180 }
181
182 static void
183 ald_startup(void *unused)
184 {
185 mtx_init(&ald_mtx, "ALDmtx", NULL, MTX_DEF|MTX_QUIET);
186 LIST_INIT(&ald_queues);
187 LIST_INIT(&ald_active);
188 }
189
190 static void
191 ald_daemon(void)
192 {
193 int needwakeup;
194 struct alq *alq;
195
196 ald_thread = FIRST_THREAD_IN_PROC(ald_proc);
197
198 alq_eventhandler_tag = EVENTHANDLER_REGISTER(shutdown_pre_sync,
199 ald_shutdown, NULL, SHUTDOWN_PRI_FIRST);
200
201 ALD_LOCK();
202
203 for (;;) {
204 while ((alq = LIST_FIRST(&ald_active)) == NULL &&
205 !ald_shutingdown)
206 mtx_sleep(&ald_active, &ald_mtx, PWAIT, "aldslp", 0);
207
208 /* Don't shutdown until all active ALQs are flushed. */
209 if (ald_shutingdown && alq == NULL) {
210 ALD_UNLOCK();
211 break;
212 }
213
214 ALQ_LOCK(alq);
215 ald_deactivate(alq);
216 ALD_UNLOCK();
217 needwakeup = alq_doio(alq);
218 ALQ_UNLOCK(alq);
219 if (needwakeup)
220 wakeup_one(alq);
221 ALD_LOCK();
222 }
223
224 kproc_exit(0);
225 }
226
227 static void
228 ald_shutdown(void *arg, int howto)
229 {
230 struct alq *alq;
231
232 ALD_LOCK();
233
234 /* Ensure no new queues can be created. */
235 ald_shutingdown = 1;
236
237 /* Shutdown all ALQs prior to terminating the ald_daemon. */
238 while ((alq = LIST_FIRST(&ald_queues)) != NULL) {
239 LIST_REMOVE(alq, aq_link);
240 ALD_UNLOCK();
241 alq_shutdown(alq);
242 ALD_LOCK();
243 }
244
245 /* At this point, all ALQs are flushed and shutdown. */
246
247 /*
248 * Wake ald_daemon so that it exits. It won't be able to do
249 * anything until we mtx_sleep because we hold the ald_mtx.
250 */
251 wakeup(&ald_active);
252
253 /* Wait for ald_daemon to exit. */
254 mtx_sleep(ald_proc, &ald_mtx, PWAIT, "aldslp", 0);
255
256 ALD_UNLOCK();
257 }
258
259 static void
260 alq_shutdown(struct alq *alq)
261 {
262 ALQ_LOCK(alq);
263
264 /* Stop any new writers. */
265 alq->aq_flags |= AQ_SHUTDOWN;
266
267 /*
268 * If the ALQ isn't active but has unwritten data (possible if
269 * the ALQ_NOACTIVATE flag has been used), explicitly activate the
270 * ALQ here so that the pending data gets flushed by the ald_daemon.
271 */
272 if (!(alq->aq_flags & AQ_ACTIVE) && HAS_PENDING_DATA(alq)) {
273 alq->aq_flags |= AQ_ACTIVE;
274 ALQ_UNLOCK(alq);
275 ALD_LOCK();
276 ald_activate(alq);
277 ALD_UNLOCK();
278 ALQ_LOCK(alq);
279 }
280
281 /* Drain IO */
282 while (alq->aq_flags & AQ_ACTIVE) {
283 alq->aq_flags |= AQ_WANTED;
284 msleep_spin(alq, &alq->aq_mtx, "aldclose", 0);
285 }
286 ALQ_UNLOCK(alq);
287
288 vn_close(alq->aq_vp, FWRITE, alq->aq_cred,
289 curthread);
290 crfree(alq->aq_cred);
291 }
292
293 void
294 alq_destroy(struct alq *alq)
295 {
296 /* Drain all pending IO. */
297 alq_shutdown(alq);
298
299 mtx_destroy(&alq->aq_mtx);
300 free(alq->aq_entbuf, M_ALD);
301 free(alq, M_ALD);
302 }
303
304 /*
305 * Flush all pending data to disk. This operation will block.
306 */
307 static int
308 alq_doio(struct alq *alq)
309 {
310 struct thread *td;
311 struct mount *mp;
312 struct vnode *vp;
313 struct uio auio;
314 struct iovec aiov[2];
315 int totlen;
316 int iov;
317 int wrapearly;
318
319 KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
320
321 vp = alq->aq_vp;
322 td = curthread;
323 totlen = 0;
324 iov = 1;
325 wrapearly = alq->aq_wrapearly;
326
327 bzero(&aiov, sizeof(aiov));
328 bzero(&auio, sizeof(auio));
329
330 /* Start the write from the location of our buffer tail pointer. */
331 aiov[0].iov_base = alq->aq_entbuf + alq->aq_writetail;
332
333 if (alq->aq_writetail < alq->aq_writehead) {
334 /* Buffer not wrapped. */
335 totlen = aiov[0].iov_len = alq->aq_writehead - alq->aq_writetail;
336 } else if (alq->aq_writehead == 0) {
337 /* Buffer not wrapped (special case to avoid an empty iov). */
338 totlen = aiov[0].iov_len = alq->aq_buflen - alq->aq_writetail -
339 wrapearly;
340 } else {
341 /*
342 * Buffer wrapped, requires 2 aiov entries:
343 * - first is from writetail to end of buffer
344 * - second is from start of buffer to writehead
345 */
346 aiov[0].iov_len = alq->aq_buflen - alq->aq_writetail -
347 wrapearly;
348 iov++;
349 aiov[1].iov_base = alq->aq_entbuf;
350 aiov[1].iov_len = alq->aq_writehead;
351 totlen = aiov[0].iov_len + aiov[1].iov_len;
352 }
353
354 alq->aq_flags |= AQ_FLUSHING;
355 ALQ_UNLOCK(alq);
356
357 auio.uio_iov = &aiov[0];
358 auio.uio_offset = 0;
359 auio.uio_segflg = UIO_SYSSPACE;
360 auio.uio_rw = UIO_WRITE;
361 auio.uio_iovcnt = iov;
362 auio.uio_resid = totlen;
363 auio.uio_td = td;
364
365 /*
366 * Do all of the junk required to write now.
367 */
368 vn_start_write(vp, &mp, V_WAIT);
369 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
370 /*
371 * XXX: VOP_WRITE error checks are ignored.
372 */
373 #ifdef MAC
374 if (mac_vnode_check_write(alq->aq_cred, NOCRED, vp) == 0)
375 #endif
376 VOP_WRITE(vp, &auio, IO_UNIT | IO_APPEND, alq->aq_cred);
377 VOP_UNLOCK(vp, 0);
378 vn_finished_write(mp);
379
380 ALQ_LOCK(alq);
381 alq->aq_flags &= ~AQ_FLUSHING;
382
383 /* Adjust writetail as required, taking into account wrapping. */
384 alq->aq_writetail = (alq->aq_writetail + totlen + wrapearly) %
385 alq->aq_buflen;
386 alq->aq_freebytes += totlen + wrapearly;
387
388 /*
389 * If we just flushed part of the buffer which wrapped, reset the
390 * wrapearly indicator.
391 */
392 if (wrapearly)
393 alq->aq_wrapearly = 0;
394
395 /*
396 * If we just flushed the buffer completely, reset indexes to 0 to
397 * minimise buffer wraps.
398 * This is also required to ensure alq_getn() can't wedge itself.
399 */
400 if (!HAS_PENDING_DATA(alq))
401 alq->aq_writehead = alq->aq_writetail = 0;
402
403 KASSERT((alq->aq_writetail >= 0 && alq->aq_writetail < alq->aq_buflen),
404 ("%s: aq_writetail < 0 || aq_writetail >= aq_buflen", __func__));
405
406 if (alq->aq_flags & AQ_WANTED) {
407 alq->aq_flags &= ~AQ_WANTED;
408 return (1);
409 }
410
411 return(0);
412 }
413
414 static struct kproc_desc ald_kp = {
415 "ALQ Daemon",
416 ald_daemon,
417 &ald_proc
418 };
419
420 SYSINIT(aldthread, SI_SUB_KTHREAD_IDLE, SI_ORDER_ANY, kproc_start, &ald_kp);
421 SYSINIT(ald, SI_SUB_LOCK, SI_ORDER_ANY, ald_startup, NULL);
422
423
424 /* User visible queue functions */
425
426 /*
427 * Create the queue data structure, allocate the buffer, and open the file.
428 */
429
430 int
431 alq_open_flags(struct alq **alqp, const char *file, struct ucred *cred, int cmode,
432 int size, int flags)
433 {
434 struct thread *td;
435 struct nameidata nd;
436 struct alq *alq;
437 int oflags;
438 int error;
439
440 KASSERT((size > 0), ("%s: size <= 0", __func__));
441
442 *alqp = NULL;
443 td = curthread;
444
445 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, file, td);
446 oflags = FWRITE | O_NOFOLLOW | O_CREAT;
447
448 error = vn_open_cred(&nd, &oflags, cmode, 0, cred, NULL);
449 if (error)
450 return (error);
451
452 NDFREE(&nd, NDF_ONLY_PNBUF);
453 /* We just unlock so we hold a reference */
454 VOP_UNLOCK(nd.ni_vp, 0);
455
456 alq = malloc(sizeof(*alq), M_ALD, M_WAITOK|M_ZERO);
457 alq->aq_vp = nd.ni_vp;
458 alq->aq_cred = crhold(cred);
459
460 mtx_init(&alq->aq_mtx, "ALD Queue", NULL, MTX_SPIN|MTX_QUIET);
461
462 alq->aq_buflen = size;
463 alq->aq_entmax = 0;
464 alq->aq_entlen = 0;
465
466 alq->aq_freebytes = alq->aq_buflen;
467 alq->aq_entbuf = malloc(alq->aq_buflen, M_ALD, M_WAITOK|M_ZERO);
468 alq->aq_writehead = alq->aq_writetail = 0;
469 if (flags & ALQ_ORDERED)
470 alq->aq_flags |= AQ_ORDERED;
471
472 if ((error = ald_add(alq)) != 0) {
473 alq_destroy(alq);
474 return (error);
475 }
476
477 *alqp = alq;
478
479 return (0);
480 }
481
482 int
483 alq_open(struct alq **alqp, const char *file, struct ucred *cred, int cmode,
484 int size, int count)
485 {
486 int ret;
487
488 KASSERT((count >= 0), ("%s: count < 0", __func__));
489
490 if (count > 0) {
491 ret = alq_open_flags(alqp, file, cred, cmode, size*count, 0);
492 (*alqp)->aq_flags |= AQ_LEGACY;
493 (*alqp)->aq_entmax = count;
494 (*alqp)->aq_entlen = size;
495 } else
496 ret = alq_open_flags(alqp, file, cred, cmode, size, 0);
497
498 return (ret);
499 }
500
501
502 /*
503 * Copy a new entry into the queue. If the operation would block either
504 * wait or return an error depending on the value of waitok.
505 */
506 int
507 alq_writen(struct alq *alq, void *data, int len, int flags)
508 {
509 int activate, copy, ret;
510 void *waitchan;
511
512 KASSERT((len > 0 && len <= alq->aq_buflen),
513 ("%s: len <= 0 || len > aq_buflen", __func__));
514
515 activate = ret = 0;
516 copy = len;
517 waitchan = NULL;
518
519 ALQ_LOCK(alq);
520
521 /*
522 * Fail to perform the write and return EWOULDBLOCK if:
523 * - The message is larger than our underlying buffer.
524 * - The ALQ is being shutdown.
525 * - There is insufficient free space in our underlying buffer
526 * to accept the message and the user can't wait for space.
527 * - There is insufficient free space in our underlying buffer
528 * to accept the message and the alq is inactive due to prior
529 * use of the ALQ_NOACTIVATE flag (which would lead to deadlock).
530 */
531 if (len > alq->aq_buflen ||
532 alq->aq_flags & AQ_SHUTDOWN ||
533 (((flags & ALQ_NOWAIT) || (!(alq->aq_flags & AQ_ACTIVE) &&
534 HAS_PENDING_DATA(alq))) && alq->aq_freebytes < len)) {
535 ALQ_UNLOCK(alq);
536 return (EWOULDBLOCK);
537 }
538
539 /*
540 * If we want ordered writes and there is already at least one thread
541 * waiting for resources to become available, sleep until we're woken.
542 */
543 if (alq->aq_flags & AQ_ORDERED && alq->aq_waiters > 0) {
544 KASSERT(!(flags & ALQ_NOWAIT),
545 ("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
546 alq->aq_waiters++;
547 msleep_spin(&alq->aq_waiters, &alq->aq_mtx, "alqwnord", 0);
548 alq->aq_waiters--;
549 }
550
551 /*
552 * (ALQ_WAITOK && aq_freebytes < len) or aq_freebytes >= len, either
553 * enter while loop and sleep until we have enough free bytes (former)
554 * or skip (latter). If AQ_ORDERED is set, only 1 thread at a time will
555 * be in this loop. Otherwise, multiple threads may be sleeping here
556 * competing for ALQ resources.
557 */
558 while (alq->aq_freebytes < len && !(alq->aq_flags & AQ_SHUTDOWN)) {
559 KASSERT(!(flags & ALQ_NOWAIT),
560 ("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
561 alq->aq_flags |= AQ_WANTED;
562 alq->aq_waiters++;
563 if (waitchan)
564 wakeup(waitchan);
565 msleep_spin(alq, &alq->aq_mtx, "alqwnres", 0);
566 alq->aq_waiters--;
567
568 /*
569 * If we're the first thread to wake after an AQ_WANTED wakeup
570 * but there isn't enough free space for us, we're going to loop
571 * and sleep again. If there are other threads waiting in this
572 * loop, schedule a wakeup so that they can see if the space
573 * they require is available.
574 */
575 if (alq->aq_waiters > 0 && !(alq->aq_flags & AQ_ORDERED) &&
576 alq->aq_freebytes < len && !(alq->aq_flags & AQ_WANTED))
577 waitchan = alq;
578 else
579 waitchan = NULL;
580 }
581
582 /*
583 * If there are waiters, we need to signal the waiting threads after we
584 * complete our work. The alq ptr is used as a wait channel for threads
585 * requiring resources to be freed up. In the AQ_ORDERED case, threads
586 * are not allowed to concurrently compete for resources in the above
587 * while loop, so we use a different wait channel in this case.
588 */
589 if (alq->aq_waiters > 0) {
590 if (alq->aq_flags & AQ_ORDERED)
591 waitchan = &alq->aq_waiters;
592 else
593 waitchan = alq;
594 } else
595 waitchan = NULL;
596
597 /* Bail if we're shutting down. */
598 if (alq->aq_flags & AQ_SHUTDOWN) {
599 ret = EWOULDBLOCK;
600 goto unlock;
601 }
602
603 /*
604 * If we need to wrap the buffer to accommodate the write,
605 * we'll need 2 calls to bcopy.
606 */
607 if ((alq->aq_buflen - alq->aq_writehead) < len)
608 copy = alq->aq_buflen - alq->aq_writehead;
609
610 /* Copy message (or part thereof if wrap required) to the buffer. */
611 bcopy(data, alq->aq_entbuf + alq->aq_writehead, copy);
612 alq->aq_writehead += copy;
613
614 if (alq->aq_writehead >= alq->aq_buflen) {
615 KASSERT((alq->aq_writehead == alq->aq_buflen),
616 ("%s: alq->aq_writehead (%d) > alq->aq_buflen (%d)",
617 __func__,
618 alq->aq_writehead,
619 alq->aq_buflen));
620 alq->aq_writehead = 0;
621 }
622
623 if (copy != len) {
624 /*
625 * Wrap the buffer by copying the remainder of our message
626 * to the start of the buffer and resetting aq_writehead.
627 */
628 bcopy(((uint8_t *)data)+copy, alq->aq_entbuf, len - copy);
629 alq->aq_writehead = len - copy;
630 }
631
632 KASSERT((alq->aq_writehead >= 0 && alq->aq_writehead < alq->aq_buflen),
633 ("%s: aq_writehead < 0 || aq_writehead >= aq_buflen", __func__));
634
635 alq->aq_freebytes -= len;
636
637 if (!(alq->aq_flags & AQ_ACTIVE) && !(flags & ALQ_NOACTIVATE)) {
638 alq->aq_flags |= AQ_ACTIVE;
639 activate = 1;
640 }
641
642 KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
643
644 unlock:
645 ALQ_UNLOCK(alq);
646
647 if (activate) {
648 ALD_LOCK();
649 ald_activate(alq);
650 ALD_UNLOCK();
651 }
652
653 /* NB: We rely on wakeup_one waking threads in a FIFO manner. */
654 if (waitchan != NULL)
655 wakeup_one(waitchan);
656
657 return (ret);
658 }
659
660 int
661 alq_write(struct alq *alq, void *data, int flags)
662 {
663 /* Should only be called in fixed length message (legacy) mode. */
664 KASSERT((alq->aq_flags & AQ_LEGACY),
665 ("%s: fixed length write on variable length queue", __func__));
666 return (alq_writen(alq, data, alq->aq_entlen, flags));
667 }
668
669 /*
670 * Retrieve a pointer for the ALQ to write directly into, avoiding bcopy.
671 */
672 struct ale *
673 alq_getn(struct alq *alq, int len, int flags)
674 {
675 int contigbytes;
676 void *waitchan;
677
678 KASSERT((len > 0 && len <= alq->aq_buflen),
679 ("%s: len <= 0 || len > alq->aq_buflen", __func__));
680
681 waitchan = NULL;
682
683 ALQ_LOCK(alq);
684
685 /*
686 * Determine the number of free contiguous bytes.
687 * We ensure elsewhere that if aq_writehead == aq_writetail because
688 * the buffer is empty, they will both be set to 0 and therefore
689 * aq_freebytes == aq_buflen and is fully contiguous.
690 * If they are equal and the buffer is not empty, aq_freebytes will
691 * be 0 indicating the buffer is full.
692 */
693 if (alq->aq_writehead <= alq->aq_writetail)
694 contigbytes = alq->aq_freebytes;
695 else {
696 contigbytes = alq->aq_buflen - alq->aq_writehead;
697
698 if (contigbytes < len) {
699 /*
700 * Insufficient space at end of buffer to handle a
701 * contiguous write. Wrap early if there's space at
702 * the beginning. This will leave a hole at the end
703 * of the buffer which we will have to skip over when
704 * flushing the buffer to disk.
705 */
706 if (alq->aq_writetail >= len || flags & ALQ_WAITOK) {
707 /* Keep track of # bytes left blank. */
708 alq->aq_wrapearly = contigbytes;
709 /* Do the wrap and adjust counters. */
710 contigbytes = alq->aq_freebytes =
711 alq->aq_writetail;
712 alq->aq_writehead = 0;
713 }
714 }
715 }
716
717 /*
718 * Return a NULL ALE if:
719 * - The message is larger than our underlying buffer.
720 * - The ALQ is being shutdown.
721 * - There is insufficient free space in our underlying buffer
722 * to accept the message and the user can't wait for space.
723 * - There is insufficient free space in our underlying buffer
724 * to accept the message and the alq is inactive due to prior
725 * use of the ALQ_NOACTIVATE flag (which would lead to deadlock).
726 */
727 if (len > alq->aq_buflen ||
728 alq->aq_flags & AQ_SHUTDOWN ||
729 (((flags & ALQ_NOWAIT) || (!(alq->aq_flags & AQ_ACTIVE) &&
730 HAS_PENDING_DATA(alq))) && contigbytes < len)) {
731 ALQ_UNLOCK(alq);
732 return (NULL);
733 }
734
735 /*
736 * If we want ordered writes and there is already at least one thread
737 * waiting for resources to become available, sleep until we're woken.
738 */
739 if (alq->aq_flags & AQ_ORDERED && alq->aq_waiters > 0) {
740 KASSERT(!(flags & ALQ_NOWAIT),
741 ("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
742 alq->aq_waiters++;
743 msleep_spin(&alq->aq_waiters, &alq->aq_mtx, "alqgnord", 0);
744 alq->aq_waiters--;
745 }
746
747 /*
748 * (ALQ_WAITOK && contigbytes < len) or contigbytes >= len, either enter
749 * while loop and sleep until we have enough contiguous free bytes
750 * (former) or skip (latter). If AQ_ORDERED is set, only 1 thread at a
751 * time will be in this loop. Otherwise, multiple threads may be
752 * sleeping here competing for ALQ resources.
753 */
754 while (contigbytes < len && !(alq->aq_flags & AQ_SHUTDOWN)) {
755 KASSERT(!(flags & ALQ_NOWAIT),
756 ("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
757 alq->aq_flags |= AQ_WANTED;
758 alq->aq_waiters++;
759 if (waitchan)
760 wakeup(waitchan);
761 msleep_spin(alq, &alq->aq_mtx, "alqgnres", 0);
762 alq->aq_waiters--;
763
764 if (alq->aq_writehead <= alq->aq_writetail)
765 contigbytes = alq->aq_freebytes;
766 else
767 contigbytes = alq->aq_buflen - alq->aq_writehead;
768
769 /*
770 * If we're the first thread to wake after an AQ_WANTED wakeup
771 * but there isn't enough free space for us, we're going to loop
772 * and sleep again. If there are other threads waiting in this
773 * loop, schedule a wakeup so that they can see if the space
774 * they require is available.
775 */
776 if (alq->aq_waiters > 0 && !(alq->aq_flags & AQ_ORDERED) &&
777 contigbytes < len && !(alq->aq_flags & AQ_WANTED))
778 waitchan = alq;
779 else
780 waitchan = NULL;
781 }
782
783 /*
784 * If there are waiters, we need to signal the waiting threads after we
785 * complete our work. The alq ptr is used as a wait channel for threads
786 * requiring resources to be freed up. In the AQ_ORDERED case, threads
787 * are not allowed to concurrently compete for resources in the above
788 * while loop, so we use a different wait channel in this case.
789 */
790 if (alq->aq_waiters > 0) {
791 if (alq->aq_flags & AQ_ORDERED)
792 waitchan = &alq->aq_waiters;
793 else
794 waitchan = alq;
795 } else
796 waitchan = NULL;
797
798 /* Bail if we're shutting down. */
799 if (alq->aq_flags & AQ_SHUTDOWN) {
800 ALQ_UNLOCK(alq);
801 if (waitchan != NULL)
802 wakeup_one(waitchan);
803 return (NULL);
804 }
805
806 /*
807 * If we are here, we have a contiguous number of bytes >= len
808 * available in our buffer starting at aq_writehead.
809 */
810 alq->aq_getpost.ae_data = alq->aq_entbuf + alq->aq_writehead;
811 alq->aq_getpost.ae_bytesused = len;
812
813 return (&alq->aq_getpost);
814 }
815
816 struct ale *
817 alq_get(struct alq *alq, int flags)
818 {
819 /* Should only be called in fixed length message (legacy) mode. */
820 KASSERT((alq->aq_flags & AQ_LEGACY),
821 ("%s: fixed length get on variable length queue", __func__));
822 return (alq_getn(alq, alq->aq_entlen, flags));
823 }
824
825 void
826 alq_post_flags(struct alq *alq, struct ale *ale, int flags)
827 {
828 int activate;
829 void *waitchan;
830
831 activate = 0;
832
833 if (ale->ae_bytesused > 0) {
834 if (!(alq->aq_flags & AQ_ACTIVE) &&
835 !(flags & ALQ_NOACTIVATE)) {
836 alq->aq_flags |= AQ_ACTIVE;
837 activate = 1;
838 }
839
840 alq->aq_writehead += ale->ae_bytesused;
841 alq->aq_freebytes -= ale->ae_bytesused;
842
843 /* Wrap aq_writehead if we filled to the end of the buffer. */
844 if (alq->aq_writehead == alq->aq_buflen)
845 alq->aq_writehead = 0;
846
847 KASSERT((alq->aq_writehead >= 0 &&
848 alq->aq_writehead < alq->aq_buflen),
849 ("%s: aq_writehead < 0 || aq_writehead >= aq_buflen",
850 __func__));
851
852 KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
853 }
854
855 /*
856 * If there are waiters, we need to signal the waiting threads after we
857 * complete our work. The alq ptr is used as a wait channel for threads
858 * requiring resources to be freed up. In the AQ_ORDERED case, threads
859 * are not allowed to concurrently compete for resources in the
860 * alq_getn() while loop, so we use a different wait channel in this case.
861 */
862 if (alq->aq_waiters > 0) {
863 if (alq->aq_flags & AQ_ORDERED)
864 waitchan = &alq->aq_waiters;
865 else
866 waitchan = alq;
867 } else
868 waitchan = NULL;
869
870 ALQ_UNLOCK(alq);
871
872 if (activate) {
873 ALD_LOCK();
874 ald_activate(alq);
875 ALD_UNLOCK();
876 }
877
878 /* NB: We rely on wakeup_one waking threads in a FIFO manner. */
879 if (waitchan != NULL)
880 wakeup_one(waitchan);
881 }
882
883 void
884 alq_flush(struct alq *alq)
885 {
886 int needwakeup = 0;
887
888 ALD_LOCK();
889 ALQ_LOCK(alq);
890
891 /*
892 * Pull the lever iff there is data to flush and we're
893 * not already in the middle of a flush operation.
894 */
895 if (HAS_PENDING_DATA(alq) && !(alq->aq_flags & AQ_FLUSHING)) {
896 if (alq->aq_flags & AQ_ACTIVE)
897 ald_deactivate(alq);
898
899 ALD_UNLOCK();
900 needwakeup = alq_doio(alq);
901 } else
902 ALD_UNLOCK();
903
904 ALQ_UNLOCK(alq);
905
906 if (needwakeup)
907 wakeup_one(alq);
908 }
909
910 /*
911 * Flush remaining data, close the file and free all resources.
912 */
913 void
914 alq_close(struct alq *alq)
915 {
916 /* Only flush and destroy alq if not already shutting down. */
917 if (ald_rem(alq) == 0)
918 alq_destroy(alq);
919 }
920
921 static int
922 alq_load_handler(module_t mod, int what, void *arg)
923 {
924 int ret;
925
926 ret = 0;
927
928 switch (what) {
929 case MOD_LOAD:
930 case MOD_SHUTDOWN:
931 break;
932
933 case MOD_QUIESCE:
934 ALD_LOCK();
935 /* Only allow unload if there are no open queues. */
936 if (LIST_FIRST(&ald_queues) == NULL) {
937 ald_shutingdown = 1;
938 ALD_UNLOCK();
939 EVENTHANDLER_DEREGISTER(shutdown_pre_sync,
940 alq_eventhandler_tag);
941 ald_shutdown(NULL, 0);
942 mtx_destroy(&ald_mtx);
943 } else {
944 ALD_UNLOCK();
945 ret = EBUSY;
946 }
947 break;
948
949 case MOD_UNLOAD:
950 /* If MOD_QUIESCE failed we must fail here too. */
951 if (ald_shutingdown == 0)
952 ret = EBUSY;
953 break;
954
955 default:
956 ret = EINVAL;
957 break;
958 }
959
960 return (ret);
961 }
962
963 static moduledata_t alq_mod =
964 {
965 "alq",
966 alq_load_handler,
967 NULL
968 };
969
970 DECLARE_MODULE(alq, alq_mod, SI_SUB_SMP, SI_ORDER_ANY);
971 MODULE_VERSION(alq, 1);
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