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 (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
23 */
24
25
26 /*
27 * VM - page locking primitives
28 */
29 #include <sys/param.h>
30 #include <sys/t_lock.h>
31 #include <sys/vtrace.h>
32 #include <sys/debug.h>
33 #include <sys/cmn_err.h>
34 #include <sys/bitmap.h>
35 #include <sys/lockstat.h>
36 #include <sys/sysmacros.h>
37 #include <sys/condvar_impl.h>
38 #include <vm/page.h>
39 #include <vm/seg_enum.h>
40 #include <vm/vm_dep.h>
41 #include <vm/seg_kmem.h>
42
43 /*
44 * This global mutex array is for logical page locking.
45 * The following fields in the page structure are protected
46 * by this lock:
47 *
48 * p_lckcnt
49 * p_cowcnt
50 */
51 pad_mutex_t page_llocks[8 * NCPU_P2];
52
53 /*
54 * This is a global lock for the logical page free list. The
55 * logical free list, in this implementation, is maintained as two
56 * separate physical lists - the cache list and the free list.
57 */
58 kmutex_t page_freelock;
59
60 /*
61 * The hash table, page_hash[], the p_selock fields, and the
62 * list of pages associated with vnodes are protected by arrays of mutexes.
63 *
64 * Unless the hashes are changed radically, the table sizes must be
65 * a power of two. Also, we typically need more mutexes for the
66 * vnodes since these locks are occasionally held for long periods.
67 * And since there seem to be two special vnodes (kvp and swapvp),
68 * we make room for private mutexes for them.
69 *
70 * The pse_mutex[] array holds the mutexes to protect the p_selock
71 * fields of all page_t structures.
72 *
73 * PAGE_SE_MUTEX(pp) returns the address of the appropriate mutex
74 * when given a pointer to a page_t.
75 *
76 * PIO_TABLE_SIZE must be a power of two. One could argue that we
77 * should go to the trouble of setting it up at run time and base it
78 * on memory size rather than the number of compile time CPUs.
79 *
80 * XX64 We should be using physmem size to calculate PIO_SHIFT.
81 *
82 * These might break in 64 bit world.
83 */
84 #define PIO_SHIFT 7 /* log2(sizeof(page_t)) */
85 #define PIO_TABLE_SIZE 128 /* number of io mutexes to have */
86
87 pad_mutex_t ph_mutex[PH_TABLE_SIZE];
88 kmutex_t pio_mutex[PIO_TABLE_SIZE];
89
90 #define PAGE_IO_MUTEX(pp) \
91 &pio_mutex[(((uintptr_t)pp) >> PIO_SHIFT) & (PIO_TABLE_SIZE - 1)]
92
93 /*
94 * The pse_mutex[] array is allocated in the platform startup code
95 * based on the size of the machine at startup.
96 */
97 extern pad_mutex_t *pse_mutex; /* Locks protecting pp->p_selock */
98 extern size_t pse_table_size; /* Number of mutexes in pse_mutex[] */
99 extern int pse_shift; /* log2(pse_table_size) */
100 #define PAGE_SE_MUTEX(pp) &pse_mutex[ \
101 ((((uintptr_t)(pp) >> pse_shift) ^ ((uintptr_t)(pp))) >> 7) & \
102 (pse_table_size - 1)].pad_mutex
103
104 #define PSZC_MTX_TABLE_SIZE 128
105 #define PSZC_MTX_TABLE_SHIFT 7
106
107 static pad_mutex_t pszc_mutex[PSZC_MTX_TABLE_SIZE];
108
109 #define PAGE_SZC_MUTEX(_pp) \
110 &pszc_mutex[((((uintptr_t)(_pp) >> PSZC_MTX_TABLE_SHIFT) ^ \
111 ((uintptr_t)(_pp) >> (PSZC_MTX_TABLE_SHIFT << 1)) ^ \
112 ((uintptr_t)(_pp) >> (3 * PSZC_MTX_TABLE_SHIFT))) & \
113 (PSZC_MTX_TABLE_SIZE - 1))].pad_mutex
114
115 /*
116 * The vph_mutex[] array holds the mutexes to protect the vnode chains,
117 * (i.e., the list of pages anchored by v_pages and connected via p_vpprev
118 * and p_vpnext).
119 *
120 * The page_vnode_mutex(vp) function returns the address of the appropriate
121 * mutex from this array given a pointer to a vnode. It is complicated
122 * by the fact that the kernel's vnode and the swapfs vnode are referenced
123 * frequently enough to warrent their own mutexes.
124 *
125 * The VP_HASH_FUNC returns the index into the vph_mutex array given
126 * an address of a vnode.
127 */
128
129 #if defined(_LP64)
130 #define VPH_TABLE_SIZE (8 * NCPU_P2)
131 #else /* 32 bits */
132 #define VPH_TABLE_SIZE (2 * NCPU_P2)
133 #endif
134
135 #define VP_HASH_FUNC(vp) \
136 ((((uintptr_t)(vp) >> 6) + \
137 ((uintptr_t)(vp) >> 8) + \
138 ((uintptr_t)(vp) >> 10) + \
139 ((uintptr_t)(vp) >> 12)) \
140 & (VPH_TABLE_SIZE - 1))
141
142 /*
143 * Two slots after VPH_TABLE_SIZE are reserved in vph_mutex for kernel vnodes.
144 * The lock for kvp is VPH_TABLE_SIZE + 0, and the lock for zvp is
145 * VPH_TABLE_SIZE + 1.
146 */
147
148 kmutex_t vph_mutex[VPH_TABLE_SIZE + 2];
149
150 /*
151 * Initialize the locks used by the Virtual Memory Management system.
152 */
153 void
154 page_lock_init()
155 {
156 }
157
158 /*
159 * Return a value for pse_shift based on npg (the number of physical pages)
160 * and ncpu (the maximum number of CPUs). This is called by platform startup
161 * code.
162 *
163 * Lockstat data from TPC-H runs showed that contention on the pse_mutex[]
164 * locks grew approximately as the square of the number of threads executing.
165 * So the primary scaling factor used is NCPU^2. The size of the machine in
166 * megabytes is used as an upper bound, particularly for sun4v machines which
167 * all claim to have 256 CPUs maximum, and the old value of PSE_TABLE_SIZE
168 * (128) is used as a minimum. Since the size of the table has to be a power
169 * of two, the calculated size is rounded up to the next power of two.
170 */
171 /*ARGSUSED*/
172 int
173 size_pse_array(pgcnt_t npg, int ncpu)
174 {
175 size_t size;
176 pgcnt_t pp_per_mb = (1024 * 1024) / PAGESIZE;
177
178 size = MAX(128, MIN(npg / pp_per_mb, 2 * ncpu * ncpu));
179 size += (1 << (highbit(size) - 1)) - 1;
180 return (highbit(size) - 1);
181 }
182
183 /*
184 * At present we only use page ownership to aid debugging, so it's
185 * OK if the owner field isn't exact. In the 32-bit world two thread ids
186 * can map to the same owner because we just 'or' in 0x80000000 and
187 * then clear the second highest bit, so that (for example) 0x2faced00
188 * and 0xafaced00 both map to 0xafaced00.
189 * In the 64-bit world, p_selock may not be large enough to hold a full
190 * thread pointer. If we ever need precise ownership (e.g. if we implement
191 * priority inheritance for page locks) then p_selock should become a
192 * uintptr_t and SE_WRITER should be -((uintptr_t)curthread >> 2).
193 */
194 #define SE_WRITER (((selock_t)(ulong_t)curthread | INT_MIN) & ~SE_EWANTED)
195 #define SE_READER 1
196
197 /*
198 * A page that is deleted must be marked as such using the
199 * page_lock_delete() function. The page must be exclusively locked.
200 * The SE_DELETED marker is put in p_selock when this function is called.
201 * SE_DELETED must be distinct from any SE_WRITER value.
202 */
203 #define SE_DELETED (1 | INT_MIN)
204
205 #ifdef VM_STATS
206 uint_t vph_kvp_count;
207 uint_t vph_swapfsvp_count;
208 uint_t vph_other;
209 #endif /* VM_STATS */
210
211 #ifdef VM_STATS
212 uint_t page_lock_count;
213 uint_t page_lock_miss;
214 uint_t page_lock_miss_lock;
215 uint_t page_lock_reclaim;
216 uint_t page_lock_bad_reclaim;
217 uint_t page_lock_same_page;
218 uint_t page_lock_upgrade;
219 uint_t page_lock_retired;
220 uint_t page_lock_upgrade_failed;
221 uint_t page_lock_deleted;
222
223 uint_t page_trylock_locked;
224 uint_t page_trylock_failed;
225 uint_t page_trylock_missed;
226
227 uint_t page_try_reclaim_upgrade;
228 #endif /* VM_STATS */
229
230 /*
231 * Acquire the "shared/exclusive" lock on a page.
232 *
233 * Returns 1 on success and locks the page appropriately.
234 * 0 on failure and does not lock the page.
235 *
236 * If `lock' is non-NULL, it will be dropped and reacquired in the
237 * failure case. This routine can block, and if it does
238 * it will always return a failure since the page identity [vp, off]
239 * or state may have changed.
240 */
241
242 int
243 page_lock(page_t *pp, se_t se, kmutex_t *lock, reclaim_t reclaim)
244 {
245 return (page_lock_es(pp, se, lock, reclaim, 0));
246 }
247
248 /*
249 * With the addition of reader-writer lock semantics to page_lock_es,
250 * callers wanting an exclusive (writer) lock may prevent shared-lock
251 * (reader) starvation by setting the es parameter to SE_EXCL_WANTED.
252 * In this case, when an exclusive lock cannot be acquired, p_selock's
253 * SE_EWANTED bit is set. Shared-lock (reader) requests are also denied
254 * if the page is slated for retirement.
255 *
256 * The se and es parameters determine if the lock should be granted
257 * based on the following decision table:
258 *
259 * Lock wanted es flags p_selock/SE_EWANTED Action
260 * ----------- -------------- ------------------- ---------
261 * SE_EXCL any [1][2] unlocked/any grant lock, clear SE_EWANTED
262 * SE_EXCL SE_EWANTED any lock/any deny, set SE_EWANTED
263 * SE_EXCL none any lock/any deny
264 * SE_SHARED n/a [2] shared/0 grant
265 * SE_SHARED n/a [2] unlocked/0 grant
266 * SE_SHARED n/a shared/1 deny
267 * SE_SHARED n/a unlocked/1 deny
268 * SE_SHARED n/a excl/any deny
269 *
270 * Notes:
271 * [1] The code grants an exclusive lock to the caller and clears the bit
272 * SE_EWANTED whenever p_selock is unlocked, regardless of the SE_EWANTED
273 * bit's value. This was deemed acceptable as we are not concerned about
274 * exclusive-lock starvation. If this ever becomes an issue, a priority or
275 * fifo mechanism should also be implemented. Meantime, the thread that
276 * set SE_EWANTED should be prepared to catch this condition and reset it
277 *
278 * [2] Retired pages may not be locked at any time, regardless of the
279 * dispostion of se, unless the es parameter has SE_RETIRED flag set.
280 *
281 * Notes on values of "es":
282 *
283 * es & 1: page_lookup_create will attempt page relocation
284 * es & SE_EXCL_WANTED: caller wants SE_EWANTED set (eg. delete
285 * memory thread); this prevents reader-starvation of waiting
286 * writer thread(s) by giving priority to writers over readers.
287 * es & SE_RETIRED: caller wants to lock pages even if they are
288 * retired. Default is to deny the lock if the page is retired.
289 *
290 * And yes, we know, the semantics of this function are too complicated.
291 * It's on the list to be cleaned up.
292 */
293 int
294 page_lock_es(page_t *pp, se_t se, kmutex_t *lock, reclaim_t reclaim, int es)
295 {
296 int retval;
297 kmutex_t *pse = PAGE_SE_MUTEX(pp);
298 int upgraded;
299 int reclaim_it;
300
301 ASSERT(lock != NULL ? MUTEX_HELD(lock) : 1);
302
303 VM_STAT_ADD(page_lock_count);
304
305 upgraded = 0;
306 reclaim_it = 0;
307
308 mutex_enter(pse);
309
310 ASSERT(((es & SE_EXCL_WANTED) == 0) ||
311 ((es & SE_EXCL_WANTED) && (se == SE_EXCL)));
312
313 if (PP_RETIRED(pp) && !(es & SE_RETIRED)) {
314 mutex_exit(pse);
315 VM_STAT_ADD(page_lock_retired);
316 return (0);
317 }
318
319 if (se == SE_SHARED && es == 1 && pp->p_selock == 0) {
320 se = SE_EXCL;
321 }
322
323 if ((reclaim == P_RECLAIM) && (PP_ISFREE(pp))) {
324
325 reclaim_it = 1;
326 if (se == SE_SHARED) {
327 /*
328 * This is an interesting situation.
329 *
330 * Remember that p_free can only change if
331 * p_selock < 0.
332 * p_free does not depend on our holding `pse'.
333 * And, since we hold `pse', p_selock can not change.
334 * So, if p_free changes on us, the page is already
335 * exclusively held, and we would fail to get p_selock
336 * regardless.
337 *
338 * We want to avoid getting the share
339 * lock on a free page that needs to be reclaimed.
340 * It is possible that some other thread has the share
341 * lock and has left the free page on the cache list.
342 * pvn_vplist_dirty() does this for brief periods.
343 * If the se_share is currently SE_EXCL, we will fail
344 * to acquire p_selock anyway. Blocking is the
345 * right thing to do.
346 * If we need to reclaim this page, we must get
347 * exclusive access to it, force the upgrade now.
348 * Again, we will fail to acquire p_selock if the
349 * page is not free and block.
350 */
351 upgraded = 1;
352 se = SE_EXCL;
353 VM_STAT_ADD(page_lock_upgrade);
354 }
355 }
356
357 if (se == SE_EXCL) {
358 if (!(es & SE_EXCL_WANTED) && (pp->p_selock & SE_EWANTED)) {
359 /*
360 * if the caller wants a writer lock (but did not
361 * specify exclusive access), and there is a pending
362 * writer that wants exclusive access, return failure
363 */
364 retval = 0;
365 } else if ((pp->p_selock & ~SE_EWANTED) == 0) {
366 /* no reader/writer lock held */
367 THREAD_KPRI_REQUEST();
368 /* this clears our setting of the SE_EWANTED bit */
369 pp->p_selock = SE_WRITER;
370 retval = 1;
371 } else {
372 /* page is locked */
373 if (es & SE_EXCL_WANTED) {
374 /* set the SE_EWANTED bit */
375 pp->p_selock |= SE_EWANTED;
376 }
377 retval = 0;
378 }
379 } else {
380 retval = 0;
381 if (pp->p_selock >= 0) {
382 if ((pp->p_selock & SE_EWANTED) == 0) {
383 pp->p_selock += SE_READER;
384 retval = 1;
385 }
386 }
387 }
388
389 if (retval == 0) {
390 if ((pp->p_selock & ~SE_EWANTED) == SE_DELETED) {
391 VM_STAT_ADD(page_lock_deleted);
392 mutex_exit(pse);
393 return (retval);
394 }
395
396 #ifdef VM_STATS
397 VM_STAT_ADD(page_lock_miss);
398 if (upgraded) {
399 VM_STAT_ADD(page_lock_upgrade_failed);
400 }
401 #endif
402 if (lock) {
403 VM_STAT_ADD(page_lock_miss_lock);
404 mutex_exit(lock);
405 }
406
407 /*
408 * Now, wait for the page to be unlocked and
409 * release the lock protecting p_cv and p_selock.
410 */
411 cv_wait(&pp->p_cv, pse);
412 mutex_exit(pse);
413
414 /*
415 * The page identity may have changed while we were
416 * blocked. If we are willing to depend on "pp"
417 * still pointing to a valid page structure (i.e.,
418 * assuming page structures are not dynamically allocated
419 * or freed), we could try to lock the page if its
420 * identity hasn't changed.
421 *
422 * This needs to be measured, since we come back from
423 * cv_wait holding pse (the expensive part of this
424 * operation) we might as well try the cheap part.
425 * Though we would also have to confirm that dropping
426 * `lock' did not cause any grief to the callers.
427 */
428 if (lock) {
429 mutex_enter(lock);
430 }
431 } else {
432 /*
433 * We have the page lock.
434 * If we needed to reclaim the page, and the page
435 * needed reclaiming (ie, it was free), then we
436 * have the page exclusively locked. We may need
437 * to downgrade the page.
438 */
439 ASSERT((upgraded) ?
440 ((PP_ISFREE(pp)) && PAGE_EXCL(pp)) : 1);
441 mutex_exit(pse);
442
443 /*
444 * We now hold this page's lock, either shared or
445 * exclusive. This will prevent its identity from changing.
446 * The page, however, may or may not be free. If the caller
447 * requested, and it is free, go reclaim it from the
448 * free list. If the page can't be reclaimed, return failure
449 * so that the caller can start all over again.
450 *
451 * NOTE:page_reclaim() releases the page lock (p_selock)
452 * if it can't be reclaimed.
453 */
454 if (reclaim_it) {
455 if (!page_reclaim(pp, lock)) {
456 VM_STAT_ADD(page_lock_bad_reclaim);
457 retval = 0;
458 } else {
459 VM_STAT_ADD(page_lock_reclaim);
460 if (upgraded) {
461 page_downgrade(pp);
462 }
463 }
464 }
465 }
466 return (retval);
467 }
468
469 /*
470 * Clear the SE_EWANTED bit from p_selock. This function allows
471 * callers of page_lock_es and page_try_reclaim_lock to clear
472 * their setting of this bit if they decide they no longer wish
473 * to gain exclusive access to the page. Currently only
474 * delete_memory_thread uses this when the delete memory
475 * operation is cancelled.
476 */
477 void
478 page_lock_clr_exclwanted(page_t *pp)
479 {
480 kmutex_t *pse = PAGE_SE_MUTEX(pp);
481
482 mutex_enter(pse);
483 pp->p_selock &= ~SE_EWANTED;
484 if (CV_HAS_WAITERS(&pp->p_cv))
485 cv_broadcast(&pp->p_cv);
486 mutex_exit(pse);
487 }
488
489 /*
490 * Read the comments inside of page_lock_es() carefully.
491 *
492 * SE_EXCL callers specifying es == SE_EXCL_WANTED will cause the
493 * SE_EWANTED bit of p_selock to be set when the lock cannot be obtained.
494 * This is used by threads subject to reader-starvation (eg. memory delete).
495 *
496 * When a thread using SE_EXCL_WANTED does not obtain the SE_EXCL lock,
497 * it is expected that it will retry at a later time. Threads that will
498 * not retry the lock *must* call page_lock_clr_exclwanted to clear the
499 * SE_EWANTED bit. (When a thread using SE_EXCL_WANTED obtains the lock,
500 * the bit is cleared.)
501 */
502 int
503 page_try_reclaim_lock(page_t *pp, se_t se, int es)
504 {
505 kmutex_t *pse = PAGE_SE_MUTEX(pp);
506 selock_t old;
507
508 mutex_enter(pse);
509
510 old = pp->p_selock;
511
512 ASSERT(((es & SE_EXCL_WANTED) == 0) ||
513 ((es & SE_EXCL_WANTED) && (se == SE_EXCL)));
514
515 if (PP_RETIRED(pp) && !(es & SE_RETIRED)) {
516 mutex_exit(pse);
517 VM_STAT_ADD(page_trylock_failed);
518 return (0);
519 }
520
521 if (se == SE_SHARED && es == 1 && old == 0) {
522 se = SE_EXCL;
523 }
524
525 if (se == SE_SHARED) {
526 if (!PP_ISFREE(pp)) {
527 if (old >= 0) {
528 /*
529 * Readers are not allowed when excl wanted
530 */
531 if ((old & SE_EWANTED) == 0) {
532 pp->p_selock = old + SE_READER;
533 mutex_exit(pse);
534 return (1);
535 }
536 }
537 mutex_exit(pse);
538 return (0);
539 }
540 /*
541 * The page is free, so we really want SE_EXCL (below)
542 */
543 VM_STAT_ADD(page_try_reclaim_upgrade);
544 }
545
546 /*
547 * The caller wants a writer lock. We try for it only if
548 * SE_EWANTED is not set, or if the caller specified
549 * SE_EXCL_WANTED.
550 */
551 if (!(old & SE_EWANTED) || (es & SE_EXCL_WANTED)) {
552 if ((old & ~SE_EWANTED) == 0) {
553 /* no reader/writer lock held */
554 THREAD_KPRI_REQUEST();
555 /* this clears out our setting of the SE_EWANTED bit */
556 pp->p_selock = SE_WRITER;
557 mutex_exit(pse);
558 return (1);
559 }
560 }
561 if (es & SE_EXCL_WANTED) {
562 /* page is locked, set the SE_EWANTED bit */
563 pp->p_selock |= SE_EWANTED;
564 }
565 mutex_exit(pse);
566 return (0);
567 }
568
569 /*
570 * Acquire a page's "shared/exclusive" lock, but never block.
571 * Returns 1 on success, 0 on failure.
572 */
573 int
574 page_trylock(page_t *pp, se_t se)
575 {
576 kmutex_t *pse = PAGE_SE_MUTEX(pp);
577
578 mutex_enter(pse);
579 if (pp->p_selock & SE_EWANTED || PP_RETIRED(pp) ||
580 (se == SE_SHARED && PP_PR_NOSHARE(pp))) {
581 /*
582 * Fail if a thread wants exclusive access and page is
583 * retired, if the page is slated for retirement, or a
584 * share lock is requested.
585 */
586 mutex_exit(pse);
587 VM_STAT_ADD(page_trylock_failed);
588 return (0);
589 }
590
591 if (se == SE_EXCL) {
592 if (pp->p_selock == 0) {
593 THREAD_KPRI_REQUEST();
594 pp->p_selock = SE_WRITER;
595 mutex_exit(pse);
596 return (1);
597 }
598 } else {
599 if (pp->p_selock >= 0) {
600 pp->p_selock += SE_READER;
601 mutex_exit(pse);
602 return (1);
603 }
604 }
605 mutex_exit(pse);
606 return (0);
607 }
608
609 /*
610 * Variant of page_unlock() specifically for the page freelist
611 * code. The mere existence of this code is a vile hack that
612 * has resulted due to the backwards locking order of the page
613 * freelist manager; please don't call it.
614 */
615 void
616 page_unlock_nocapture(page_t *pp)
617 {
618 kmutex_t *pse = PAGE_SE_MUTEX(pp);
619 selock_t old;
620
621 mutex_enter(pse);
622
623 old = pp->p_selock;
624 if ((old & ~SE_EWANTED) == SE_READER) {
625 pp->p_selock = old & ~SE_READER;
626 if (CV_HAS_WAITERS(&pp->p_cv))
627 cv_broadcast(&pp->p_cv);
628 } else if ((old & ~SE_EWANTED) == SE_DELETED) {
629 panic("page_unlock_nocapture: page %p is deleted", (void *)pp);
630 } else if (old < 0) {
631 THREAD_KPRI_RELEASE();
632 pp->p_selock &= SE_EWANTED;
633 if (CV_HAS_WAITERS(&pp->p_cv))
634 cv_broadcast(&pp->p_cv);
635 } else if ((old & ~SE_EWANTED) > SE_READER) {
636 pp->p_selock = old - SE_READER;
637 } else {
638 panic("page_unlock_nocapture: page %p is not locked",
639 (void *)pp);
640 }
641
642 mutex_exit(pse);
643 }
644
645 /*
646 * Release the page's "shared/exclusive" lock and wake up anyone
647 * who might be waiting for it.
648 */
649 void
650 page_unlock(page_t *pp)
651 {
652 kmutex_t *pse = PAGE_SE_MUTEX(pp);
653 selock_t old;
654
655 mutex_enter(pse);
656
657 old = pp->p_selock;
658 if ((old & ~SE_EWANTED) == SE_READER) {
659 pp->p_selock = old & ~SE_READER;
660 if (CV_HAS_WAITERS(&pp->p_cv))
661 cv_broadcast(&pp->p_cv);
662 } else if ((old & ~SE_EWANTED) == SE_DELETED) {
663 panic("page_unlock: page %p is deleted", (void *)pp);
664 } else if (old < 0) {
665 THREAD_KPRI_RELEASE();
666 pp->p_selock &= SE_EWANTED;
667 if (CV_HAS_WAITERS(&pp->p_cv))
668 cv_broadcast(&pp->p_cv);
669 } else if ((old & ~SE_EWANTED) > SE_READER) {
670 pp->p_selock = old - SE_READER;
671 } else {
672 panic("page_unlock: page %p is not locked", (void *)pp);
673 }
674
675 if (pp->p_selock == 0) {
676 /*
677 * If the T_CAPTURING bit is set, that means that we should
678 * not try and capture the page again as we could recurse
679 * which could lead to a stack overflow panic or spending a
680 * relatively long time in the kernel making no progress.
681 */
682 if ((pp->p_toxic & PR_CAPTURE) &&
683 !(curthread->t_flag & T_CAPTURING) &&
684 !PP_RETIRED(pp)) {
685 THREAD_KPRI_REQUEST();
686 pp->p_selock = SE_WRITER;
687 mutex_exit(pse);
688 page_unlock_capture(pp);
689 } else {
690 mutex_exit(pse);
691 }
692 } else {
693 mutex_exit(pse);
694 }
695 }
696
697 /*
698 * Try to upgrade the lock on the page from a "shared" to an
699 * "exclusive" lock. Since this upgrade operation is done while
700 * holding the mutex protecting this page, no one else can acquire this page's
701 * lock and change the page. Thus, it is safe to drop the "shared"
702 * lock and attempt to acquire the "exclusive" lock.
703 *
704 * Returns 1 on success, 0 on failure.
705 */
706 int
707 page_tryupgrade(page_t *pp)
708 {
709 kmutex_t *pse = PAGE_SE_MUTEX(pp);
710
711 mutex_enter(pse);
712 if (!(pp->p_selock & SE_EWANTED)) {
713 /* no threads want exclusive access, try upgrade */
714 if (pp->p_selock == SE_READER) {
715 THREAD_KPRI_REQUEST();
716 /* convert to exclusive lock */
717 pp->p_selock = SE_WRITER;
718 mutex_exit(pse);
719 return (1);
720 }
721 }
722 mutex_exit(pse);
723 return (0);
724 }
725
726 /*
727 * Downgrade the "exclusive" lock on the page to a "shared" lock
728 * while holding the mutex protecting this page's p_selock field.
729 */
730 void
731 page_downgrade(page_t *pp)
732 {
733 kmutex_t *pse = PAGE_SE_MUTEX(pp);
734 int excl_waiting;
735
736 ASSERT((pp->p_selock & ~SE_EWANTED) != SE_DELETED);
737 ASSERT(PAGE_EXCL(pp));
738
739 mutex_enter(pse);
740 excl_waiting = pp->p_selock & SE_EWANTED;
741 THREAD_KPRI_RELEASE();
742 pp->p_selock = SE_READER | excl_waiting;
743 if (CV_HAS_WAITERS(&pp->p_cv))
744 cv_broadcast(&pp->p_cv);
745 mutex_exit(pse);
746 }
747
748 void
749 page_lock_delete(page_t *pp)
750 {
751 kmutex_t *pse = PAGE_SE_MUTEX(pp);
752
753 ASSERT(PAGE_EXCL(pp));
754 ASSERT(pp->p_vnode == NULL);
755 ASSERT(pp->p_offset == (u_offset_t)-1);
756 ASSERT(!PP_ISFREE(pp));
757
758 mutex_enter(pse);
759 THREAD_KPRI_RELEASE();
760 pp->p_selock = SE_DELETED;
761 if (CV_HAS_WAITERS(&pp->p_cv))
762 cv_broadcast(&pp->p_cv);
763 mutex_exit(pse);
764 }
765
766 int
767 page_deleted(page_t *pp)
768 {
769 return (pp->p_selock == SE_DELETED);
770 }
771
772 /*
773 * Implement the io lock for pages
774 */
775 void
776 page_iolock_init(page_t *pp)
777 {
778 pp->p_iolock_state = 0;
779 cv_init(&pp->p_io_cv, NULL, CV_DEFAULT, NULL);
780 }
781
782 /*
783 * Acquire the i/o lock on a page.
784 */
785 void
786 page_io_lock(page_t *pp)
787 {
788 kmutex_t *pio;
789
790 pio = PAGE_IO_MUTEX(pp);
791 mutex_enter(pio);
792 while (pp->p_iolock_state & PAGE_IO_INUSE) {
793 cv_wait(&(pp->p_io_cv), pio);
794 }
795 pp->p_iolock_state |= PAGE_IO_INUSE;
796 mutex_exit(pio);
797 }
798
799 /*
800 * Release the i/o lock on a page.
801 */
802 void
803 page_io_unlock(page_t *pp)
804 {
805 kmutex_t *pio;
806
807 pio = PAGE_IO_MUTEX(pp);
808 mutex_enter(pio);
809 cv_broadcast(&pp->p_io_cv);
810 pp->p_iolock_state &= ~PAGE_IO_INUSE;
811 mutex_exit(pio);
812 }
813
814 /*
815 * Try to acquire the i/o lock on a page without blocking.
816 * Returns 1 on success, 0 on failure.
817 */
818 int
819 page_io_trylock(page_t *pp)
820 {
821 kmutex_t *pio;
822
823 if (pp->p_iolock_state & PAGE_IO_INUSE)
824 return (0);
825
826 pio = PAGE_IO_MUTEX(pp);
827 mutex_enter(pio);
828
829 if (pp->p_iolock_state & PAGE_IO_INUSE) {
830 mutex_exit(pio);
831 return (0);
832 }
833 pp->p_iolock_state |= PAGE_IO_INUSE;
834 mutex_exit(pio);
835
836 return (1);
837 }
838
839 /*
840 * Wait until the i/o lock is not held.
841 */
842 void
843 page_io_wait(page_t *pp)
844 {
845 kmutex_t *pio;
846
847 pio = PAGE_IO_MUTEX(pp);
848 mutex_enter(pio);
849 while (pp->p_iolock_state & PAGE_IO_INUSE) {
850 cv_wait(&(pp->p_io_cv), pio);
851 }
852 mutex_exit(pio);
853 }
854
855 /*
856 * Returns 1 on success, 0 on failure.
857 */
858 int
859 page_io_locked(page_t *pp)
860 {
861 return (pp->p_iolock_state & PAGE_IO_INUSE);
862 }
863
864 /*
865 * Assert that the i/o lock on a page is held.
866 * Returns 1 on success, 0 on failure.
867 */
868 int
869 page_iolock_assert(page_t *pp)
870 {
871 return (page_io_locked(pp));
872 }
873
874 /*
875 * Wrapper exported to kernel routines that are built
876 * platform-independent (the macro is platform-dependent;
877 * the size of vph_mutex[] is based on NCPU).
878 *
879 * Note that you can do stress testing on this by setting the
880 * variable page_vnode_mutex_stress to something other than
881 * zero in a DEBUG kernel in a debugger after loading the kernel.
882 * Setting it after the kernel is running may not work correctly.
883 */
884 #ifdef DEBUG
885 static int page_vnode_mutex_stress = 0;
886 #endif
887
888 kmutex_t *
889 page_vnode_mutex(vnode_t *vp)
890 {
891 if (vp == &kvp)
892 return (&vph_mutex[VPH_TABLE_SIZE + 0]);
893
894 if (vp == &zvp)
895 return (&vph_mutex[VPH_TABLE_SIZE + 1]);
896 #ifdef DEBUG
897 if (page_vnode_mutex_stress != 0)
898 return (&vph_mutex[0]);
899 #endif
900
901 return (&vph_mutex[VP_HASH_FUNC(vp)]);
902 }
903
904 kmutex_t *
905 page_se_mutex(page_t *pp)
906 {
907 return (PAGE_SE_MUTEX(pp));
908 }
909
910 #ifdef VM_STATS
911 uint_t pszclck_stat[4];
912 #endif
913 /*
914 * Find, take and return a mutex held by hat_page_demote().
915 * Called by page_demote_vp_pages() before hat_page_demote() call and by
916 * routines that want to block hat_page_demote() but can't do it
917 * via locking all constituent pages.
918 *
919 * Return NULL if p_szc is 0.
920 *
921 * It should only be used for pages that can be demoted by hat_page_demote()
922 * i.e. non swapfs file system pages. The logic here is lifted from
923 * sfmmu_mlspl_enter() except there's no need to worry about p_szc increase
924 * since the page is locked and not free.
925 *
926 * Hash of the root page is used to find the lock.
927 * To find the root in the presense of hat_page_demote() chageing the location
928 * of the root this routine relies on the fact that hat_page_demote() changes
929 * root last.
930 *
931 * If NULL is returned pp's p_szc is guaranteed to be 0. If non NULL is
932 * returned pp's p_szc may be any value.
933 */
934 kmutex_t *
935 page_szc_lock(page_t *pp)
936 {
937 kmutex_t *mtx;
938 page_t *rootpp;
939 uint_t szc;
940 uint_t rszc;
941 uint_t pszc = pp->p_szc;
942
943 ASSERT(pp != NULL);
944 ASSERT(PAGE_LOCKED(pp));
945 ASSERT(!PP_ISFREE(pp));
946 ASSERT(pp->p_vnode != NULL);
947 ASSERT(!IS_SWAPFSVP(pp->p_vnode));
948 ASSERT(!PP_ISKAS(pp));
949
950 again:
951 if (pszc == 0) {
952 VM_STAT_ADD(pszclck_stat[0]);
953 return (NULL);
954 }
955
956 /* The lock lives in the root page */
957
958 rootpp = PP_GROUPLEADER(pp, pszc);
959 mtx = PAGE_SZC_MUTEX(rootpp);
960 mutex_enter(mtx);
961
962 /*
963 * since p_szc can only decrease if pp == rootpp
964 * rootpp will be always the same i.e we have the right root
965 * regardless of rootpp->p_szc.
966 * If location of pp's root didn't change after we took
967 * the lock we have the right root. return mutex hashed off it.
968 */
969 if (pp == rootpp || (rszc = rootpp->p_szc) == pszc) {
970 VM_STAT_ADD(pszclck_stat[1]);
971 return (mtx);
972 }
973
974 /*
975 * root location changed because page got demoted.
976 * locate the new root.
977 */
978 if (rszc < pszc) {
979 szc = pp->p_szc;
980 ASSERT(szc < pszc);
981 mutex_exit(mtx);
982 pszc = szc;
983 VM_STAT_ADD(pszclck_stat[2]);
984 goto again;
985 }
986
987 VM_STAT_ADD(pszclck_stat[3]);
988 /*
989 * current hat_page_demote not done yet.
990 * wait for it to finish.
991 */
992 mutex_exit(mtx);
993 rootpp = PP_GROUPLEADER(rootpp, rszc);
994 mtx = PAGE_SZC_MUTEX(rootpp);
995 mutex_enter(mtx);
996 mutex_exit(mtx);
997 ASSERT(rootpp->p_szc < rszc);
998 goto again;
999 }
1000
1001 int
1002 page_szc_lock_assert(page_t *pp)
1003 {
1004 page_t *rootpp = PP_PAGEROOT(pp);
1005 kmutex_t *mtx = PAGE_SZC_MUTEX(rootpp);
1006
1007 return (MUTEX_HELD(mtx));
1008 }
1009
1010 /*
1011 * memseg locking
1012 */
1013 static krwlock_t memsegslock;
1014
1015 /*
1016 * memlist (phys_install, phys_avail) locking.
1017 */
1018 static krwlock_t memlists_lock;
1019
1020 int
1021 memsegs_trylock(int writer)
1022 {
1023 return (rw_tryenter(&memsegslock, writer ? RW_WRITER : RW_READER));
1024 }
1025
1026 void
1027 memsegs_lock(int writer)
1028 {
1029 rw_enter(&memsegslock, writer ? RW_WRITER : RW_READER);
1030 }
1031
1032 /*ARGSUSED*/
1033 void
1034 memsegs_unlock(int writer)
1035 {
1036 rw_exit(&memsegslock);
1037 }
1038
1039 int
1040 memsegs_lock_held(void)
1041 {
1042 return (RW_LOCK_HELD(&memsegslock));
1043 }
1044
1045 void
1046 memlist_read_lock(void)
1047 {
1048 rw_enter(&memlists_lock, RW_READER);
1049 }
1050
1051 void
1052 memlist_read_unlock(void)
1053 {
1054 rw_exit(&memlists_lock);
1055 }
1056
1057 void
1058 memlist_write_lock(void)
1059 {
1060 rw_enter(&memlists_lock, RW_WRITER);
1061 }
1062
1063 void
1064 memlist_write_unlock(void)
1065 {
1066 rw_exit(&memlists_lock);
1067 }