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1.1 root 1: /*
2: * Mach Operating System
3: * Copyright (c) 1991,1990,1989 Carnegie Mellon University
4: * All Rights Reserved.
5: *
6: * Permission to use, copy, modify and distribute this software and its
7: * documentation is hereby granted, provided that both the copyright
8: * notice and this permission notice appear in all copies of the
9: * software, derivative works or modified versions, and any portions
10: * thereof, and that both notices appear in supporting documentation.
11: *
12: * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
13: * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
14: * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
15: *
16: * Carnegie Mellon requests users of this software to return to
17: *
18: * Software Distribution Coordinator or [email protected]
19: * School of Computer Science
20: * Carnegie Mellon University
21: * Pittsburgh PA 15213-3890
22: *
23: * any improvements or extensions that they make and grant Carnegie Mellon
24: * the rights to redistribute these changes.
25: */
26: /*
27: * File: ipc/ipc_hash.c
28: * Author: Rich Draves
29: * Date: 1989
30: *
31: * Entry hash table operations.
32: */
33:
34: #include <mach/boolean.h>
35: #include <mach/port.h>
36: #include <kern/lock.h>
37: #include <kern/kalloc.h>
38: #include <ipc/port.h>
39: #include <ipc/ipc_space.h>
40: #include <ipc/ipc_object.h>
41: #include <ipc/ipc_entry.h>
42: #include <ipc/ipc_hash.h>
43: #include <ipc/ipc_init.h>
44: #include <ipc/ipc_types.h>
45:
46: #include <mach_ipc_debug.h>
47: #if MACH_IPC_DEBUG
48: #include <mach/kern_return.h>
49: #include <mach_debug/hash_info.h>
50: #include <vm/vm_map.h>
51: #include <vm/vm_kern.h>
52: #include <vm/vm_user.h>
53: #endif
54:
55:
56:
57: /*
58: * Routine: ipc_hash_lookup
59: * Purpose:
60: * Converts (space, obj) -> (name, entry).
61: * Returns TRUE if an entry was found.
62: * Conditions:
63: * The space must be locked (read or write) throughout.
64: */
65:
66: boolean_t
67: ipc_hash_lookup(space, obj, namep, entryp)
68: ipc_space_t space;
69: ipc_object_t obj;
70: mach_port_t *namep;
71: ipc_entry_t *entryp;
72: {
73: return (ipc_hash_local_lookup(space, obj, namep, entryp) ||
74: ((space->is_tree_hash > 0) &&
75: ipc_hash_global_lookup(space, obj, namep,
76: (ipc_tree_entry_t *) entryp)));
77: }
78:
79: /*
80: * Routine: ipc_hash_insert
81: * Purpose:
82: * Inserts an entry into the appropriate reverse hash table,
83: * so that ipc_hash_lookup will find it.
84: * Conditions:
85: * The space must be write-locked.
86: */
87:
88: void
89: ipc_hash_insert(
90: ipc_space_t space,
91: ipc_object_t obj,
92: mach_port_t name,
93: ipc_entry_t entry)
94: {
95: mach_port_index_t index;
96:
97: index = MACH_PORT_INDEX(name);
98: if ((index < space->is_table_size) &&
99: (entry == &space->is_table[index]))
100: ipc_hash_local_insert(space, obj, index, entry);
101: else
102: ipc_hash_global_insert(space, obj, name,
103: (ipc_tree_entry_t) entry);
104: }
105:
106: /*
107: * Routine: ipc_hash_delete
108: * Purpose:
109: * Deletes an entry from the appropriate reverse hash table.
110: * Conditions:
111: * The space must be write-locked.
112: */
113:
114: void
115: ipc_hash_delete(
116: ipc_space_t space,
117: ipc_object_t obj,
118: mach_port_t name,
119: ipc_entry_t entry)
120: {
121: mach_port_index_t index;
122:
123: index = MACH_PORT_INDEX(name);
124: if ((index < space->is_table_size) &&
125: (entry == &space->is_table[index]))
126: ipc_hash_local_delete(space, obj, index, entry);
127: else
128: ipc_hash_global_delete(space, obj, name,
129: (ipc_tree_entry_t) entry);
130: }
131:
132: /*
133: * The global reverse hash table holds splay tree entries.
134: * It is a simple open-chaining hash table with singly-linked buckets.
135: * Each bucket is locked separately, with an exclusive lock.
136: * Within each bucket, move-to-front is used.
137: */
138:
139: ipc_hash_index_t ipc_hash_global_size;
140: ipc_hash_index_t ipc_hash_global_mask;
141:
142: #define IH_GLOBAL_HASH(space, obj) \
143: (((((ipc_hash_index_t) ((vm_offset_t)space)) >> 4) + \
144: (((ipc_hash_index_t) ((vm_offset_t)obj)) >> 6)) & \
145: ipc_hash_global_mask)
146:
147: typedef struct ipc_hash_global_bucket {
148: decl_simple_lock_data(, ihgb_lock_data)
149: ipc_tree_entry_t ihgb_head;
150: } *ipc_hash_global_bucket_t;
151:
152: #define IHGB_NULL ((ipc_hash_global_bucket_t) 0)
153:
154: #define ihgb_lock_init(ihgb) simple_lock_init(&(ihgb)->ihgb_lock_data)
155: #define ihgb_lock(ihgb) simple_lock(&(ihgb)->ihgb_lock_data)
156: #define ihgb_unlock(ihgb) simple_unlock(&(ihgb)->ihgb_lock_data)
157:
158: ipc_hash_global_bucket_t ipc_hash_global_table;
159:
160: /*
161: * Routine: ipc_hash_global_lookup
162: * Purpose:
163: * Converts (space, obj) -> (name, entry).
164: * Looks in the global table, for splay tree entries.
165: * Returns TRUE if an entry was found.
166: * Conditions:
167: * The space must be locked (read or write) throughout.
168: */
169:
170: boolean_t
171: ipc_hash_global_lookup(
172: ipc_space_t space,
173: ipc_object_t obj,
174: mach_port_t *namep,
175: ipc_tree_entry_t *entryp)
176: {
177: ipc_hash_global_bucket_t bucket;
178: ipc_tree_entry_t this, *last;
179:
180: assert(space != IS_NULL);
181: assert(obj != IO_NULL);
182:
183: bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
184: ihgb_lock(bucket);
185:
186: if ((this = bucket->ihgb_head) != ITE_NULL) {
187: if ((this->ite_object == obj) &&
188: (this->ite_space == space)) {
189: /* found it at front; no need to move */
190:
191: *namep = this->ite_name;
192: *entryp = this;
193: } else for (last = &this->ite_next;
194: (this = *last) != ITE_NULL;
195: last = &this->ite_next) {
196: if ((this->ite_object == obj) &&
197: (this->ite_space == space)) {
198: /* found it; move to front */
199:
200: *last = this->ite_next;
201: this->ite_next = bucket->ihgb_head;
202: bucket->ihgb_head = this;
203:
204: *namep = this->ite_name;
205: *entryp = this;
206: break;
207: }
208: }
209: }
210:
211: ihgb_unlock(bucket);
212: return this != ITE_NULL;
213: }
214:
215: /*
216: * Routine: ipc_hash_global_insert
217: * Purpose:
218: * Inserts an entry into the global reverse hash table.
219: * Conditions:
220: * The space must be write-locked.
221: */
222:
223: void
224: ipc_hash_global_insert(
225: ipc_space_t space,
226: ipc_object_t obj,
227: mach_port_t name,
228: ipc_tree_entry_t entry)
229: {
230: ipc_hash_global_bucket_t bucket;
231:
232:
233: assert(entry->ite_name == name);
234: assert(space != IS_NULL);
235: assert(entry->ite_space == space);
236: assert(obj != IO_NULL);
237: assert(entry->ite_object == obj);
238:
239: space->is_tree_hash++;
240: assert(space->is_tree_hash <= space->is_tree_total);
241:
242: bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
243: ihgb_lock(bucket);
244:
245: /* insert at front of bucket */
246:
247: entry->ite_next = bucket->ihgb_head;
248: bucket->ihgb_head = entry;
249:
250: ihgb_unlock(bucket);
251: }
252:
253: /*
254: * Routine: ipc_hash_global_delete
255: * Purpose:
256: * Deletes an entry from the global reverse hash table.
257: * Conditions:
258: * The space must be write-locked.
259: */
260:
261: void
262: ipc_hash_global_delete(
263: ipc_space_t space,
264: ipc_object_t obj,
265: mach_port_t name,
266: ipc_tree_entry_t entry)
267: {
268: ipc_hash_global_bucket_t bucket;
269: ipc_tree_entry_t this, *last;
270:
271: assert(entry->ite_name == name);
272: assert(space != IS_NULL);
273: assert(entry->ite_space == space);
274: assert(obj != IO_NULL);
275: assert(entry->ite_object == obj);
276:
277: assert(space->is_tree_hash > 0);
278: space->is_tree_hash--;
279:
280: bucket = &ipc_hash_global_table[IH_GLOBAL_HASH(space, obj)];
281: ihgb_lock(bucket);
282:
283: for (last = &bucket->ihgb_head;
284: (this = *last) != ITE_NULL;
285: last = &this->ite_next) {
286: if (this == entry) {
287: /* found it; remove from bucket */
288:
289: *last = this->ite_next;
290: break;
291: }
292: }
293: assert(this != ITE_NULL);
294:
295: ihgb_unlock(bucket);
296: }
297:
298: /*
299: * Each space has a local reverse hash table, which holds
300: * entries from the space's table. In fact, the hash table
301: * just uses a field (ie_index) in the table itself.
302: *
303: * The local hash table is an open-addressing hash table,
304: * which means that when a collision occurs, instead of
305: * throwing the entry into a bucket, the entry is rehashed
306: * to another position in the table. In this case the rehash
307: * is very simple: linear probing (ie, just increment the position).
308: * This simple rehash makes deletions tractable (they're still a pain),
309: * but it means that collisions tend to build up into clumps.
310: *
311: * Because at least one entry in the table (index 0) is always unused,
312: * there will always be room in the reverse hash table. If a table
313: * with n slots gets completely full, the reverse hash table will
314: * have one giant clump of n-1 slots and one free slot somewhere.
315: * Because entries are only entered into the reverse table if they
316: * are pure send rights (not receive, send-once, port-set,
317: * or dead-name rights), and free entries of course aren't entered,
318: * I expect the reverse hash table won't get unreasonably full.
319: *
320: * Ordered hash tables (Amble & Knuth, Computer Journal, v. 17, no. 2,
321: * pp. 135-142.) may be desirable here. They can dramatically help
322: * unsuccessful lookups. But unsuccessful lookups are almost always
323: * followed by insertions, and those slow down somewhat. They
324: * also can help deletions somewhat. Successful lookups aren't affected.
325: * So possibly a small win; probably nothing significant.
326: */
327:
328: #define IH_LOCAL_HASH(obj, size) \
329: ((((mach_port_index_t) (obj)) >> 6) % (size))
330:
331: /*
332: * Routine: ipc_hash_local_lookup
333: * Purpose:
334: * Converts (space, obj) -> (name, entry).
335: * Looks in the space's local table, for table entries.
336: * Returns TRUE if an entry was found.
337: * Conditions:
338: * The space must be locked (read or write) throughout.
339: */
340:
341: boolean_t
342: ipc_hash_local_lookup(
343: ipc_space_t space,
344: ipc_object_t obj,
345: mach_port_t *namep,
346: ipc_entry_t *entryp)
347: {
348: ipc_entry_t table;
349: ipc_entry_num_t size;
350: mach_port_index_t hindex, index;
351:
352: assert(space != IS_NULL);
353: assert(obj != IO_NULL);
354:
355: table = space->is_table;
356: size = space->is_table_size;
357: hindex = IH_LOCAL_HASH(obj, size);
358:
359: /*
360: * Ideally, table[hindex].ie_index is the name we want.
361: * However, must check ie_object to verify this,
362: * because collisions can happen. In case of a collision,
363: * search farther along in the clump.
364: */
365:
366: while ((index = table[hindex].ie_index) != 0) {
367: ipc_entry_t entry = &table[index];
368:
369: if (entry->ie_object == obj) {
370: *namep = MACH_PORT_MAKEB(index, entry->ie_bits);
371: *entryp = entry;
372: return TRUE;
373: }
374:
375: if (++hindex == size)
376: hindex = 0;
377: }
378:
379: return FALSE;
380: }
381:
382: /*
383: * Routine: ipc_hash_local_insert
384: * Purpose:
385: * Inserts an entry into the space's reverse hash table.
386: * Conditions:
387: * The space must be write-locked.
388: */
389:
390: void
391: ipc_hash_local_insert(
392: ipc_space_t space,
393: ipc_object_t obj,
394: mach_port_index_t index,
395: ipc_entry_t entry)
396: {
397: ipc_entry_t table;
398: ipc_entry_num_t size;
399: mach_port_index_t hindex;
400:
401: assert(index != 0);
402: assert(space != IS_NULL);
403: assert(obj != IO_NULL);
404:
405: table = space->is_table;
406: size = space->is_table_size;
407: hindex = IH_LOCAL_HASH(obj, size);
408:
409: assert(entry == &table[index]);
410: assert(entry->ie_object == obj);
411:
412: /*
413: * We want to insert at hindex, but there may be collisions.
414: * If a collision occurs, search for the end of the clump
415: * and insert there.
416: */
417:
418: while (table[hindex].ie_index != 0) {
419: if (++hindex == size)
420: hindex = 0;
421: }
422:
423: table[hindex].ie_index = index;
424: }
425:
426: /*
427: * Routine: ipc_hash_local_delete
428: * Purpose:
429: * Deletes an entry from the space's reverse hash table.
430: * Conditions:
431: * The space must be write-locked.
432: */
433:
434: void
435: ipc_hash_local_delete(
436: ipc_space_t space,
437: ipc_object_t obj,
438: mach_port_index_t index,
439: ipc_entry_t entry)
440: {
441: ipc_entry_t table;
442: ipc_entry_num_t size;
443: mach_port_index_t hindex, dindex;
444:
445: assert(index != MACH_PORT_NULL);
446: assert(space != IS_NULL);
447: assert(obj != IO_NULL);
448:
449: table = space->is_table;
450: size = space->is_table_size;
451: hindex = IH_LOCAL_HASH(obj, size);
452:
453: assert(entry == &table[index]);
454: assert(entry->ie_object == obj);
455:
456: /*
457: * First check we have the right hindex for this index.
458: * In case of collision, we have to search farther
459: * along in this clump.
460: */
461:
462: while (table[hindex].ie_index != index) {
463: if (table[hindex].ie_index == 0)
464: {
465: static int gak = 0;
466: if (gak == 0)
467: {
468: printf("gak! entry wasn't in hash table!\n");
469: gak = 1;
470: }
471: return;
472: }
473: if (++hindex == size)
474: hindex = 0;
475: }
476:
477: /*
478: * Now we want to set table[hindex].ie_index = 0.
479: * But if we aren't the last index in a clump,
480: * this might cause problems for lookups of objects
481: * farther along in the clump that are displaced
482: * due to collisions. Searches for them would fail
483: * at hindex instead of succeeding.
484: *
485: * So we must check the clump after hindex for objects
486: * that are so displaced, and move one up to the new hole.
487: *
488: * hindex - index of new hole in the clump
489: * dindex - index we are checking for a displaced object
490: *
491: * When we move a displaced object up into the hole,
492: * it creates a new hole, and we have to repeat the process
493: * until we get to the end of the clump.
494: */
495:
496: for (dindex = hindex; index != 0; hindex = dindex) {
497: for (;;) {
498: mach_port_index_t tindex;
499: ipc_object_t tobj;
500:
501: if (++dindex == size)
502: dindex = 0;
503: assert(dindex != hindex);
504:
505: /* are we at the end of the clump? */
506:
507: index = table[dindex].ie_index;
508: if (index == 0)
509: break;
510:
511: /* is this a displaced object? */
512:
513: tobj = table[index].ie_object;
514: assert(tobj != IO_NULL);
515: tindex = IH_LOCAL_HASH(tobj, size);
516:
517: if ((dindex < hindex) ?
518: ((dindex < tindex) && (tindex <= hindex)) :
519: ((dindex < tindex) || (tindex <= hindex)))
520: break;
521: }
522:
523: table[hindex].ie_index = index;
524: }
525: }
526:
527: /*
528: * Routine: ipc_hash_init
529: * Purpose:
530: * Initialize the reverse hash table implementation.
531: */
532:
533: void
534: ipc_hash_init(void)
535: {
536: ipc_hash_index_t i;
537:
538: /* if not configured, initialize ipc_hash_global_size */
539:
540: if (ipc_hash_global_size == 0) {
541: ipc_hash_global_size = ipc_tree_entry_max >> 8;
542: if (ipc_hash_global_size < 32)
543: ipc_hash_global_size = 32;
544: }
545:
546: /* make sure it is a power of two */
547:
548: ipc_hash_global_mask = ipc_hash_global_size - 1;
549: if ((ipc_hash_global_size & ipc_hash_global_mask) != 0) {
550: natural_t bit;
551:
552: /* round up to closest power of two */
553:
554: for (bit = 1;; bit <<= 1) {
555: ipc_hash_global_mask |= bit;
556: ipc_hash_global_size = ipc_hash_global_mask + 1;
557:
558: if ((ipc_hash_global_size & ipc_hash_global_mask) == 0)
559: break;
560: }
561: }
562:
563: /* allocate ipc_hash_global_table */
564:
565: ipc_hash_global_table = (ipc_hash_global_bucket_t)
566: kalloc((vm_size_t) (ipc_hash_global_size *
567: sizeof(struct ipc_hash_global_bucket)));
568: assert(ipc_hash_global_table != IHGB_NULL);
569:
570: /* and initialize it */
571:
572: for (i = 0; i < ipc_hash_global_size; i++) {
573: ipc_hash_global_bucket_t bucket;
574:
575: bucket = &ipc_hash_global_table[i];
576: ihgb_lock_init(bucket);
577: bucket->ihgb_head = ITE_NULL;
578: }
579: }
580:
581: #if MACH_IPC_DEBUG
582:
583: /*
584: * Routine: ipc_hash_info
585: * Purpose:
586: * Return information about the global reverse hash table.
587: * Fills the buffer with as much information as possible
588: * and returns the desired size of the buffer.
589: * Conditions:
590: * Nothing locked. The caller should provide
591: * possibly-pageable memory.
592: */
593:
594:
595: ipc_hash_index_t
596: ipc_hash_info(
597: hash_info_bucket_t *info,
598: mach_msg_type_number_t count)
599: {
600: ipc_hash_index_t i;
601:
602: if (ipc_hash_global_size < count)
603: count = ipc_hash_global_size;
604:
605: for (i = 0; i < count; i++) {
606: ipc_hash_global_bucket_t bucket = &ipc_hash_global_table[i];
607: unsigned int bucket_count = 0;
608: ipc_tree_entry_t entry;
609:
610: ihgb_lock(bucket);
611: for (entry = bucket->ihgb_head;
612: entry != ITE_NULL;
613: entry = entry->ite_next)
614: bucket_count++;
615: ihgb_unlock(bucket);
616:
617: /* don't touch pageable memory while holding locks */
618: info[i].hib_count = bucket_count;
619: }
620:
621: return ipc_hash_global_size;
622: }
623:
624: #endif /* MACH_IPC_DEBUG */
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