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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*********************************************************************
2 *
3 * Filename: irqueue.c
4 * Version: 0.3
5 * Description: General queue implementation
6 * Status: Experimental.
7 * Author: Dag Brattli <dagb@cs.uit.no>
8 * Created at: Tue Jun 9 13:29:31 1998
9 * Modified at: Sun Dec 12 13:48:22 1999
10 * Modified by: Dag Brattli <dagb@cs.uit.no>
11 * Modified at: Thu Jan 4 14:29:10 CET 2001
12 * Modified by: Marc Zyngier <mzyngier@freesurf.fr>
13 *
14 * Copyright (C) 1998-1999, Aage Kvalnes <aage@cs.uit.no>
15 * Copyright (C) 1998, Dag Brattli,
16 * All Rights Reserved.
17 *
18 * This code is taken from the Vortex Operating System written by Aage
19 * Kvalnes. Aage has agreed that this code can use the GPL licence,
20 * although he does not use that licence in his own code.
21 *
22 * This copyright does however _not_ include the ELF hash() function
23 * which I currently don't know which licence or copyright it
24 * has. Please inform me if you know.
25 *
26 * This program is free software; you can redistribute it and/or
27 * modify it under the terms of the GNU General Public License as
28 * published by the Free Software Foundation; either version 2 of
29 * the License, or (at your option) any later version.
30 *
31 * Neither Dag Brattli nor University of Tromsø admit liability nor
32 * provide warranty for any of this software. This material is
33 * provided "AS-IS" and at no charge.
34 *
35 ********************************************************************/
36
37/*
38 * NOTE :
39 * There are various problems with this package :
40 * o the hash function for ints is pathetic (but could be changed)
41 * o locking is sometime suspicious (especially during enumeration)
42 * o most users have only a few elements (== overhead)
43 * o most users never use seach, so don't benefit from hashing
44 * Problem already fixed :
45 * o not 64 bit compliant (most users do hashv = (int) self)
46 * o hashbin_remove() is broken => use hashbin_remove_this()
47 * I think most users would be better served by a simple linked list
48 * (like include/linux/list.h) with a global spinlock per list.
49 * Jean II
50 */
51
52/*
53 * Notes on the concurrent access to hashbin and other SMP issues
54 * -------------------------------------------------------------
55 * Hashbins are very often in the IrDA stack a global repository of
56 * information, and therefore used in a very asynchronous manner following
57 * various events (driver calls, timers, user calls...).
58 * Therefore, very often it is highly important to consider the
59 * management of concurrent access to the hashbin and how to guarantee the
60 * consistency of the operations on it.
61 *
62 * First, we need to define the objective of locking :
63 * 1) Protect user data (content pointed by the hashbin)
64 * 2) Protect hashbin structure itself (linked list in each bin)
65 *
66 * OLD LOCKING
67 * -----------
68 *
69 * The previous locking strategy, either HB_LOCAL or HB_GLOBAL were
70 * both inadequate in *both* aspect.
71 * o HB_GLOBAL was using a spinlock for each bin (local locking).
72 * o HB_LOCAL was disabling irq on *all* CPUs, so use a single
73 * global semaphore.
74 * The problems were :
75 * A) Global irq disabling is no longer supported by the kernel
76 * B) No protection for the hashbin struct global data
77 * o hashbin_delete()
78 * o hb_current
79 * C) No protection for user data in some cases
80 *
81 * A) HB_LOCAL use global irq disabling, so doesn't work on kernel
82 * 2.5.X. Even when it is supported (kernel 2.4.X and earlier), its
83 * performance is not satisfactory on SMP setups. Most hashbins were
84 * HB_LOCAL, so (A) definitely need fixing.
85 * B) HB_LOCAL could be modified to fix (B). However, because HB_GLOBAL
86 * lock only the individual bins, it will never be able to lock the
87 * global data, so can't do (B).
88 * C) Some functions return pointer to data that is still in the
89 * hashbin :
90 * o hashbin_find()
91 * o hashbin_get_first()
92 * o hashbin_get_next()
93 * As the data is still in the hashbin, it may be changed or free'd
94 * while the caller is examinimg the data. In those case, locking can't
95 * be done within the hashbin, but must include use of the data within
96 * the caller.
97 * The caller can easily do this with HB_LOCAL (just disable irqs).
98 * However, this is impossible with HB_GLOBAL because the caller has no
99 * way to know the proper bin, so don't know which spinlock to use.
100 *
101 * Quick summary : can no longer use HB_LOCAL, and HB_GLOBAL is
102 * fundamentally broken and will never work.
103 *
104 * NEW LOCKING
105 * -----------
106 *
107 * To fix those problems, I've introduce a few changes in the
108 * hashbin locking :
109 * 1) New HB_LOCK scheme
110 * 2) hashbin->hb_spinlock
111 * 3) New hashbin usage policy
112 *
113 * HB_LOCK :
114 * -------
115 * HB_LOCK is a locking scheme intermediate between the old HB_LOCAL
116 * and HB_GLOBAL. It uses a single spinlock to protect the whole content
117 * of the hashbin. As it is a single spinlock, it can protect the global
118 * data of the hashbin and not only the bins themselves.
119 * HB_LOCK can only protect some of the hashbin calls, so it only lock
120 * call that can be made 100% safe and leave other call unprotected.
121 * HB_LOCK in theory is slower than HB_GLOBAL, but as the hashbin
122 * content is always small contention is not high, so it doesn't matter
123 * much. HB_LOCK is probably faster than HB_LOCAL.
124 *
125 * hashbin->hb_spinlock :
126 * --------------------
127 * The spinlock that HB_LOCK uses is available for caller, so that
128 * the caller can protect unprotected calls (see below).
129 * If the caller want to do entirely its own locking (HB_NOLOCK), he
130 * can do so and may use safely this spinlock.
131 * Locking is done like this :
132 * spin_lock_irqsave(&hashbin->hb_spinlock, flags);
133 * Releasing the lock :
134 * spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
135 *
136 * Safe & Protected calls :
137 * ----------------------
138 * The following calls are safe or protected via HB_LOCK :
139 * o hashbin_new() -> safe
140 * o hashbin_delete()
141 * o hashbin_insert()
142 * o hashbin_remove_first()
143 * o hashbin_remove()
144 * o hashbin_remove_this()
145 * o HASHBIN_GET_SIZE() -> atomic
146 *
147 * The following calls only protect the hashbin itself :
148 * o hashbin_lock_find()
149 * o hashbin_find_next()
150 *
151 * Unprotected calls :
152 * -----------------
153 * The following calls need to be protected by the caller :
154 * o hashbin_find()
155 * o hashbin_get_first()
156 * o hashbin_get_next()
157 *
158 * Locking Policy :
159 * --------------
160 * If the hashbin is used only in a single thread of execution
161 * (explicitly or implicitely), you can use HB_NOLOCK
162 * If the calling module already provide concurrent access protection,
163 * you may use HB_NOLOCK.
164 *
165 * In all other cases, you need to use HB_LOCK and lock the hashbin
166 * every time before calling one of the unprotected calls. You also must
167 * use the pointer returned by the unprotected call within the locked
168 * region.
169 *
170 * Extra care for enumeration :
171 * --------------------------
172 * hashbin_get_first() and hashbin_get_next() use the hashbin to
173 * store the current position, in hb_current.
174 * As long as the hashbin remains locked, this is safe. If you unlock
175 * the hashbin, the current position may change if anybody else modify
176 * or enumerate the hashbin.
177 * Summary : do the full enumeration while locked.
178 *
179 * Alternatively, you may use hashbin_find_next(). But, this will
180 * be slower, is more complex to use and doesn't protect the hashbin
181 * content. So, care is needed here as well.
182 *
183 * Other issues :
184 * ------------
185 * I believe that we are overdoing it by using spin_lock_irqsave()
186 * and we should use only spin_lock_bh() or similar. But, I don't have
187 * the balls to try it out.
188 * Don't believe that because hashbin are now (somewhat) SMP safe
189 * that the rest of the code is. Higher layers tend to be safest,
190 * but LAP and LMP would need some serious dedicated love.
191 *
192 * Jean II
193 */
194#include <linux/module.h>
195
196#include <net/irda/irda.h>
197#include <net/irda/irqueue.h>
198
199/************************ QUEUE SUBROUTINES ************************/
200
201/*
202 * Hashbin
203 */
204#define GET_HASHBIN(x) ( x & HASHBIN_MASK )
205
206/*
207 * Function hash (name)
208 *
209 * This function hash the input string 'name' using the ELF hash
210 * function for strings.
211 */
212static __u32 hash( const char* name)
213{
214 __u32 h = 0;
215 __u32 g;
216
217 while(*name) {
218 h = (h<<4) + *name++;
219 if ((g = (h & 0xf0000000)))
220 h ^=g>>24;
221 h &=~g;
222 }
223 return h;
224}
225
226/*
227 * Function enqueue_first (queue, proc)
228 *
229 * Insert item first in queue.
230 *
231 */
232static void enqueue_first(irda_queue_t **queue, irda_queue_t* element)
233{
234
235 IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);
236
237 /*
238 * Check if queue is empty.
239 */
240 if ( *queue == NULL ) {
241 /*
242 * Queue is empty. Insert one element into the queue.
243 */
244 element->q_next = element->q_prev = *queue = element;
245
246 } else {
247 /*
248 * Queue is not empty. Insert element into front of queue.
249 */
250 element->q_next = (*queue);
251 (*queue)->q_prev->q_next = element;
252 element->q_prev = (*queue)->q_prev;
253 (*queue)->q_prev = element;
254 (*queue) = element;
255 }
256}
257
258
259/*
260 * Function dequeue (queue)
261 *
262 * Remove first entry in queue
263 *
264 */
265static irda_queue_t *dequeue_first(irda_queue_t **queue)
266{
267 irda_queue_t *ret;
268
269 IRDA_DEBUG( 4, "dequeue_first()\n");
270
271 /*
272 * Set return value
273 */
274 ret = *queue;
275
276 if ( *queue == NULL ) {
277 /*
278 * Queue was empty.
279 */
280 } else if ( (*queue)->q_next == *queue ) {
281 /*
282 * Queue only contained a single element. It will now be
283 * empty.
284 */
285 *queue = NULL;
286 } else {
287 /*
288 * Queue contained several element. Remove the first one.
289 */
290 (*queue)->q_prev->q_next = (*queue)->q_next;
291 (*queue)->q_next->q_prev = (*queue)->q_prev;
292 *queue = (*queue)->q_next;
293 }
294
295 /*
296 * Return the removed entry (or NULL of queue was empty).
297 */
298 return ret;
299}
300
301/*
302 * Function dequeue_general (queue, element)
303 *
304 *
305 */
306static irda_queue_t *dequeue_general(irda_queue_t **queue, irda_queue_t* element)
307{
308 irda_queue_t *ret;
309
310 IRDA_DEBUG( 4, "dequeue_general()\n");
311
312 /*
313 * Set return value
314 */
315 ret = *queue;
316
317 if ( *queue == NULL ) {
318 /*
319 * Queue was empty.
320 */
321 } else if ( (*queue)->q_next == *queue ) {
322 /*
323 * Queue only contained a single element. It will now be
324 * empty.
325 */
326 *queue = NULL;
327
328 } else {
329 /*
330 * Remove specific element.
331 */
332 element->q_prev->q_next = element->q_next;
333 element->q_next->q_prev = element->q_prev;
334 if ( (*queue) == element)
335 (*queue) = element->q_next;
336 }
337
338 /*
339 * Return the removed entry (or NULL of queue was empty).
340 */
341 return ret;
342}
343
344/************************ HASHBIN MANAGEMENT ************************/
345
346/*
347 * Function hashbin_create ( type, name )
348 *
349 * Create hashbin!
350 *
351 */
352hashbin_t *hashbin_new(int type)
353{
354 hashbin_t* hashbin;
355
356 /*
357 * Allocate new hashbin
358 */
359 hashbin = kmalloc( sizeof(hashbin_t), GFP_ATOMIC);
360 if (!hashbin)
361 return NULL;
362
363 /*
364 * Initialize structure
365 */
366 memset(hashbin, 0, sizeof(hashbin_t));
367 hashbin->hb_type = type;
368 hashbin->magic = HB_MAGIC;
369 //hashbin->hb_current = NULL;
370
371 /* Make sure all spinlock's are unlocked */
372 if ( hashbin->hb_type & HB_LOCK ) {
373 spin_lock_init(&hashbin->hb_spinlock);
374 }
375
376 return hashbin;
377}
378EXPORT_SYMBOL(hashbin_new);
379
380
381/*
382 * Function hashbin_delete (hashbin, free_func)
383 *
384 * Destroy hashbin, the free_func can be a user supplied special routine
385 * for deallocating this structure if it's complex. If not the user can
386 * just supply kfree, which should take care of the job.
387 */
388int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
389{
390 irda_queue_t* queue;
391 unsigned long flags = 0;
392 int i;
393
394 IRDA_ASSERT(hashbin != NULL, return -1;);
395 IRDA_ASSERT(hashbin->magic == HB_MAGIC, return -1;);
396
397 /* Synchronize */
398 if ( hashbin->hb_type & HB_LOCK ) {
399 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
400 }
401
402 /*
403 * Free the entries in the hashbin, TODO: use hashbin_clear when
404 * it has been shown to work
405 */
406 for (i = 0; i < HASHBIN_SIZE; i ++ ) {
407 queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
408 while (queue ) {
409 if (free_func)
410 (*free_func)(queue);
411 queue = dequeue_first(
412 (irda_queue_t**) &hashbin->hb_queue[i]);
413 }
414 }
415
416 /* Cleanup local data */
417 hashbin->hb_current = NULL;
418 hashbin->magic = ~HB_MAGIC;
419
420 /* Release lock */
421 if ( hashbin->hb_type & HB_LOCK) {
422 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
423 }
424
425 /*
426 * Free the hashbin structure
427 */
428 kfree(hashbin);
429
430 return 0;
431}
432EXPORT_SYMBOL(hashbin_delete);
433
434/********************* HASHBIN LIST OPERATIONS *********************/
435
436/*
437 * Function hashbin_insert (hashbin, entry, name)
438 *
439 * Insert an entry into the hashbin
440 *
441 */
442void hashbin_insert(hashbin_t* hashbin, irda_queue_t* entry, long hashv,
443 const char* name)
444{
445 unsigned long flags = 0;
446 int bin;
447
448 IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);
449
450 IRDA_ASSERT( hashbin != NULL, return;);
451 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return;);
452
453 /*
454 * Locate hashbin
455 */
456 if ( name )
457 hashv = hash( name );
458 bin = GET_HASHBIN( hashv );
459
460 /* Synchronize */
461 if ( hashbin->hb_type & HB_LOCK ) {
462 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
463 } /* Default is no-lock */
464
465 /*
466 * Store name and key
467 */
468 entry->q_hash = hashv;
469 if ( name )
470 strlcpy( entry->q_name, name, sizeof(entry->q_name));
471
472 /*
473 * Insert new entry first
474 */
475 enqueue_first( (irda_queue_t**) &hashbin->hb_queue[ bin ],
476 entry);
477 hashbin->hb_size++;
478
479 /* Release lock */
480 if ( hashbin->hb_type & HB_LOCK ) {
481 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
482 } /* Default is no-lock */
483}
484EXPORT_SYMBOL(hashbin_insert);
485
486/*
487 * Function hashbin_remove_first (hashbin)
488 *
489 * Remove first entry of the hashbin
490 *
491 * Note : this function no longer use hashbin_remove(), but does things
492 * similar to hashbin_remove_this(), so can be considered safe.
493 * Jean II
494 */
495void *hashbin_remove_first( hashbin_t *hashbin)
496{
497 unsigned long flags = 0;
498 irda_queue_t *entry = NULL;
499
500 /* Synchronize */
501 if ( hashbin->hb_type & HB_LOCK ) {
502 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
503 } /* Default is no-lock */
504
505 entry = hashbin_get_first( hashbin);
506 if ( entry != NULL) {
507 int bin;
508 long hashv;
509 /*
510 * Locate hashbin
511 */
512 hashv = entry->q_hash;
513 bin = GET_HASHBIN( hashv );
514
515 /*
516 * Dequeue the entry...
517 */
518 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
519 (irda_queue_t*) entry );
520 hashbin->hb_size--;
521 entry->q_next = NULL;
522 entry->q_prev = NULL;
523
524 /*
525 * Check if this item is the currently selected item, and in
526 * that case we must reset hb_current
527 */
528 if ( entry == hashbin->hb_current)
529 hashbin->hb_current = NULL;
530 }
531
532 /* Release lock */
533 if ( hashbin->hb_type & HB_LOCK ) {
534 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
535 } /* Default is no-lock */
536
537 return entry;
538}
539
540
541/*
542 * Function hashbin_remove (hashbin, hashv, name)
543 *
544 * Remove entry with the given name
545 *
546 * The use of this function is highly discouraged, because the whole
547 * concept behind hashbin_remove() is broken. In many cases, it's not
548 * possible to guarantee the unicity of the index (either hashv or name),
549 * leading to removing the WRONG entry.
550 * The only simple safe use is :
551 * hashbin_remove(hasbin, (int) self, NULL);
552 * In other case, you must think hard to guarantee unicity of the index.
553 * Jean II
554 */
555void* hashbin_remove( hashbin_t* hashbin, long hashv, const char* name)
556{
557 int bin, found = FALSE;
558 unsigned long flags = 0;
559 irda_queue_t* entry;
560
561 IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);
562
563 IRDA_ASSERT( hashbin != NULL, return NULL;);
564 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
565
566 /*
567 * Locate hashbin
568 */
569 if ( name )
570 hashv = hash( name );
571 bin = GET_HASHBIN( hashv );
572
573 /* Synchronize */
574 if ( hashbin->hb_type & HB_LOCK ) {
575 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
576 } /* Default is no-lock */
577
578 /*
579 * Search for entry
580 */
581 entry = hashbin->hb_queue[ bin ];
582 if ( entry ) {
583 do {
584 /*
585 * Check for key
586 */
587 if ( entry->q_hash == hashv ) {
588 /*
589 * Name compare too?
590 */
591 if ( name ) {
592 if ( strcmp( entry->q_name, name) == 0)
593 {
594 found = TRUE;
595 break;
596 }
597 } else {
598 found = TRUE;
599 break;
600 }
601 }
602 entry = entry->q_next;
603 } while ( entry != hashbin->hb_queue[ bin ] );
604 }
605
606 /*
607 * If entry was found, dequeue it
608 */
609 if ( found ) {
610 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
611 (irda_queue_t*) entry );
612 hashbin->hb_size--;
613
614 /*
615 * Check if this item is the currently selected item, and in
616 * that case we must reset hb_current
617 */
618 if ( entry == hashbin->hb_current)
619 hashbin->hb_current = NULL;
620 }
621
622 /* Release lock */
623 if ( hashbin->hb_type & HB_LOCK ) {
624 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
625 } /* Default is no-lock */
626
627
628 /* Return */
629 if ( found )
630 return entry;
631 else
632 return NULL;
633
634}
635EXPORT_SYMBOL(hashbin_remove);
636
637/*
638 * Function hashbin_remove_this (hashbin, entry)
639 *
640 * Remove entry with the given name
641 *
642 * In some cases, the user of hashbin can't guarantee the unicity
643 * of either the hashv or name.
644 * In those cases, using the above function is guaranteed to cause troubles,
645 * so we use this one instead...
646 * And by the way, it's also faster, because we skip the search phase ;-)
647 */
648void* hashbin_remove_this( hashbin_t* hashbin, irda_queue_t* entry)
649{
650 unsigned long flags = 0;
651 int bin;
652 long hashv;
653
654 IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);
655
656 IRDA_ASSERT( hashbin != NULL, return NULL;);
657 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
658 IRDA_ASSERT( entry != NULL, return NULL;);
659
660 /* Synchronize */
661 if ( hashbin->hb_type & HB_LOCK ) {
662 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
663 } /* Default is no-lock */
664
665 /* Check if valid and not already removed... */
666 if((entry->q_next == NULL) || (entry->q_prev == NULL)) {
667 entry = NULL;
668 goto out;
669 }
670
671 /*
672 * Locate hashbin
673 */
674 hashv = entry->q_hash;
675 bin = GET_HASHBIN( hashv );
676
677 /*
678 * Dequeue the entry...
679 */
680 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
681 (irda_queue_t*) entry );
682 hashbin->hb_size--;
683 entry->q_next = NULL;
684 entry->q_prev = NULL;
685
686 /*
687 * Check if this item is the currently selected item, and in
688 * that case we must reset hb_current
689 */
690 if ( entry == hashbin->hb_current)
691 hashbin->hb_current = NULL;
692out:
693 /* Release lock */
694 if ( hashbin->hb_type & HB_LOCK ) {
695 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
696 } /* Default is no-lock */
697
698 return entry;
699}
700EXPORT_SYMBOL(hashbin_remove_this);
701
702/*********************** HASHBIN ENUMERATION ***********************/
703
704/*
705 * Function hashbin_common_find (hashbin, hashv, name)
706 *
707 * Find item with the given hashv or name
708 *
709 */
710void* hashbin_find( hashbin_t* hashbin, long hashv, const char* name )
711{
712 int bin;
713 irda_queue_t* entry;
714
715 IRDA_DEBUG( 4, "hashbin_find()\n");
716
717 IRDA_ASSERT( hashbin != NULL, return NULL;);
718 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
719
720 /*
721 * Locate hashbin
722 */
723 if ( name )
724 hashv = hash( name );
725 bin = GET_HASHBIN( hashv );
726
727 /*
728 * Search for entry
729 */
730 entry = hashbin->hb_queue[ bin];
731 if ( entry ) {
732 do {
733 /*
734 * Check for key
735 */
736 if ( entry->q_hash == hashv ) {
737 /*
738 * Name compare too?
739 */
740 if ( name ) {
741 if ( strcmp( entry->q_name, name ) == 0 ) {
742 return entry;
743 }
744 } else {
745 return entry;
746 }
747 }
748 entry = entry->q_next;
749 } while ( entry != hashbin->hb_queue[ bin ] );
750 }
751
752 return NULL;
753}
754EXPORT_SYMBOL(hashbin_find);
755
756/*
757 * Function hashbin_lock_find (hashbin, hashv, name)
758 *
759 * Find item with the given hashv or name
760 *
761 * Same, but with spinlock protection...
762 * I call it safe, but it's only safe with respect to the hashbin, not its
763 * content. - Jean II
764 */
765void* hashbin_lock_find( hashbin_t* hashbin, long hashv, const char* name )
766{
767 unsigned long flags = 0;
768 irda_queue_t* entry;
769
770 /* Synchronize */
771 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
772
773 /*
774 * Search for entry
775 */
776 entry = (irda_queue_t* ) hashbin_find( hashbin, hashv, name );
777
778 /* Release lock */
779 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
780
781 return entry;
782}
783EXPORT_SYMBOL(hashbin_lock_find);
784
785/*
786 * Function hashbin_find (hashbin, hashv, name, pnext)
787 *
788 * Find an item with the given hashv or name, and its successor
789 *
790 * This function allow to do concurrent enumerations without the
791 * need to lock over the whole session, because the caller keep the
792 * context of the search. On the other hand, it might fail and return
793 * NULL if the entry is removed. - Jean II
794 */
795void* hashbin_find_next( hashbin_t* hashbin, long hashv, const char* name,
796 void ** pnext)
797{
798 unsigned long flags = 0;
799 irda_queue_t* entry;
800
801 /* Synchronize */
802 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
803
804 /*
805 * Search for current entry
806 * This allow to check if the current item is still in the
807 * hashbin or has been removed.
808 */
809 entry = (irda_queue_t* ) hashbin_find( hashbin, hashv, name );
810
811 /*
812 * Trick hashbin_get_next() to return what we want
813 */
814 if(entry) {
815 hashbin->hb_current = entry;
816 *pnext = hashbin_get_next( hashbin );
817 } else
818 *pnext = NULL;
819
820 /* Release lock */
821 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
822
823 return entry;
824}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825
826/*
827 * Function hashbin_get_first (hashbin)
828 *
829 * Get a pointer to first element in hashbin, this function must be
830 * called before any calls to hashbin_get_next()!
831 *
832 */
833irda_queue_t *hashbin_get_first( hashbin_t* hashbin)
834{
835 irda_queue_t *entry;
836 int i;
837
838 IRDA_ASSERT( hashbin != NULL, return NULL;);
839 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
840
841 if ( hashbin == NULL)
842 return NULL;
843
844 for ( i = 0; i < HASHBIN_SIZE; i ++ ) {
845 entry = hashbin->hb_queue[ i];
846 if ( entry) {
847 hashbin->hb_current = entry;
848 return entry;
849 }
850 }
851 /*
852 * Did not find any item in hashbin
853 */
854 return NULL;
855}
856EXPORT_SYMBOL(hashbin_get_first);
857
858/*
859 * Function hashbin_get_next (hashbin)
860 *
861 * Get next item in hashbin. A series of hashbin_get_next() calls must
862 * be started by a call to hashbin_get_first(). The function returns
863 * NULL when all items have been traversed
864 *
865 * The context of the search is stored within the hashbin, so you must
866 * protect yourself from concurrent enumerations. - Jean II
867 */
868irda_queue_t *hashbin_get_next( hashbin_t *hashbin)
869{
870 irda_queue_t* entry;
871 int bin;
872 int i;
873
874 IRDA_ASSERT( hashbin != NULL, return NULL;);
875 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
876
877 if ( hashbin->hb_current == NULL) {
878 IRDA_ASSERT( hashbin->hb_current != NULL, return NULL;);
879 return NULL;
880 }
881 entry = hashbin->hb_current->q_next;
882 bin = GET_HASHBIN( entry->q_hash);
883
884 /*
885 * Make sure that we are not back at the beginning of the queue
886 * again
887 */
888 if ( entry != hashbin->hb_queue[ bin ]) {
889 hashbin->hb_current = entry;
890
891 return entry;
892 }
893
894 /*
895 * Check that this is not the last queue in hashbin
896 */
897 if ( bin >= HASHBIN_SIZE)
898 return NULL;
899
900 /*
901 * Move to next queue in hashbin
902 */
903 bin++;
904 for ( i = bin; i < HASHBIN_SIZE; i++ ) {
905 entry = hashbin->hb_queue[ i];
906 if ( entry) {
907 hashbin->hb_current = entry;
908
909 return entry;
910 }
911 }
912 return NULL;
913}
914EXPORT_SYMBOL(hashbin_get_next);