1 /*********************************************************************
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 search, 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 #include <linux/slab.h>
196
197 #include <net/irda/irda.h>
198 #include <net/irda/irqueue.h>
199
200 /************************ QUEUE SUBROUTINES ************************/
201
202 /*
203 * Hashbin
204 */
205 #define GET_HASHBIN(x) ( x & HASHBIN_MASK )
206
207 /*
208 * Function hash (name)
209 *
210 * This function hash the input string 'name' using the ELF hash
211 * function for strings.
212 */
hash(const char * name)213 static __u32 hash( const char* name)
214 {
215 __u32 h = 0;
216 __u32 g;
217
218 while(*name) {
219 h = (h<<4) + *name++;
220 if ((g = (h & 0xf0000000)))
221 h ^=g>>24;
222 h &=~g;
223 }
224 return h;
225 }
226
227 /*
228 * Function enqueue_first (queue, proc)
229 *
230 * Insert item first in queue.
231 *
232 */
enqueue_first(irda_queue_t ** queue,irda_queue_t * element)233 static void enqueue_first(irda_queue_t **queue, irda_queue_t* element)
234 {
235
236 /*
237 * Check if queue is empty.
238 */
239 if ( *queue == NULL ) {
240 /*
241 * Queue is empty. Insert one element into the queue.
242 */
243 element->q_next = element->q_prev = *queue = element;
244
245 } else {
246 /*
247 * Queue is not empty. Insert element into front of queue.
248 */
249 element->q_next = (*queue);
250 (*queue)->q_prev->q_next = element;
251 element->q_prev = (*queue)->q_prev;
252 (*queue)->q_prev = element;
253 (*queue) = element;
254 }
255 }
256
257
258 /*
259 * Function dequeue (queue)
260 *
261 * Remove first entry in queue
262 *
263 */
dequeue_first(irda_queue_t ** queue)264 static irda_queue_t *dequeue_first(irda_queue_t **queue)
265 {
266 irda_queue_t *ret;
267
268 pr_debug("dequeue_first()\n");
269
270 /*
271 * Set return value
272 */
273 ret = *queue;
274
275 if ( *queue == NULL ) {
276 /*
277 * Queue was empty.
278 */
279 } else if ( (*queue)->q_next == *queue ) {
280 /*
281 * Queue only contained a single element. It will now be
282 * empty.
283 */
284 *queue = NULL;
285 } else {
286 /*
287 * Queue contained several element. Remove the first one.
288 */
289 (*queue)->q_prev->q_next = (*queue)->q_next;
290 (*queue)->q_next->q_prev = (*queue)->q_prev;
291 *queue = (*queue)->q_next;
292 }
293
294 /*
295 * Return the removed entry (or NULL of queue was empty).
296 */
297 return ret;
298 }
299
300 /*
301 * Function dequeue_general (queue, element)
302 *
303 *
304 */
dequeue_general(irda_queue_t ** queue,irda_queue_t * element)305 static irda_queue_t *dequeue_general(irda_queue_t **queue, irda_queue_t* element)
306 {
307 irda_queue_t *ret;
308
309 pr_debug("dequeue_general()\n");
310
311 /*
312 * Set return value
313 */
314 ret = *queue;
315
316 if ( *queue == NULL ) {
317 /*
318 * Queue was empty.
319 */
320 } else if ( (*queue)->q_next == *queue ) {
321 /*
322 * Queue only contained a single element. It will now be
323 * empty.
324 */
325 *queue = NULL;
326
327 } else {
328 /*
329 * Remove specific element.
330 */
331 element->q_prev->q_next = element->q_next;
332 element->q_next->q_prev = element->q_prev;
333 if ( (*queue) == element)
334 (*queue) = element->q_next;
335 }
336
337 /*
338 * Return the removed entry (or NULL of queue was empty).
339 */
340 return ret;
341 }
342
343 /************************ HASHBIN MANAGEMENT ************************/
344
345 /*
346 * Function hashbin_create ( type, name )
347 *
348 * Create hashbin!
349 *
350 */
hashbin_new(int type)351 hashbin_t *hashbin_new(int type)
352 {
353 hashbin_t* hashbin;
354
355 /*
356 * Allocate new hashbin
357 */
358 hashbin = kzalloc(sizeof(*hashbin), GFP_ATOMIC);
359 if (!hashbin)
360 return NULL;
361
362 /*
363 * Initialize structure
364 */
365 hashbin->hb_type = type;
366 hashbin->magic = HB_MAGIC;
367 //hashbin->hb_current = NULL;
368
369 /* Make sure all spinlock's are unlocked */
370 if ( hashbin->hb_type & HB_LOCK ) {
371 spin_lock_init(&hashbin->hb_spinlock);
372 }
373
374 return hashbin;
375 }
376 EXPORT_SYMBOL(hashbin_new);
377
378
379 /*
380 * Function hashbin_delete (hashbin, free_func)
381 *
382 * Destroy hashbin, the free_func can be a user supplied special routine
383 * for deallocating this structure if it's complex. If not the user can
384 * just supply kfree, which should take care of the job.
385 */
hashbin_delete(hashbin_t * hashbin,FREE_FUNC free_func)386 int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
387 {
388 irda_queue_t* queue;
389 unsigned long flags = 0;
390 int i;
391
392 IRDA_ASSERT(hashbin != NULL, return -1;);
393 IRDA_ASSERT(hashbin->magic == HB_MAGIC, return -1;);
394
395 /* Synchronize */
396 if (hashbin->hb_type & HB_LOCK)
397 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
398
399 /*
400 * Free the entries in the hashbin, TODO: use hashbin_clear when
401 * it has been shown to work
402 */
403 for (i = 0; i < HASHBIN_SIZE; i ++ ) {
404 while (1) {
405 queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
406
407 if (!queue)
408 break;
409
410 if (free_func) {
411 if (hashbin->hb_type & HB_LOCK)
412 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
413 free_func(queue);
414 if (hashbin->hb_type & HB_LOCK)
415 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
416 }
417 }
418 }
419
420 /* Cleanup local data */
421 hashbin->hb_current = NULL;
422 hashbin->magic = ~HB_MAGIC;
423
424 /* Release lock */
425 if (hashbin->hb_type & HB_LOCK)
426 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
427
428 /*
429 * Free the hashbin structure
430 */
431 kfree(hashbin);
432
433 return 0;
434 }
435 EXPORT_SYMBOL(hashbin_delete);
436
437 /********************* HASHBIN LIST OPERATIONS *********************/
438
439 /*
440 * Function hashbin_insert (hashbin, entry, name)
441 *
442 * Insert an entry into the hashbin
443 *
444 */
hashbin_insert(hashbin_t * hashbin,irda_queue_t * entry,long hashv,const char * name)445 void hashbin_insert(hashbin_t* hashbin, irda_queue_t* entry, long hashv,
446 const char* name)
447 {
448 unsigned long flags = 0;
449 int bin;
450
451 IRDA_ASSERT( hashbin != NULL, return;);
452 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return;);
453
454 /*
455 * Locate hashbin
456 */
457 if ( name )
458 hashv = hash( name );
459 bin = GET_HASHBIN( hashv );
460
461 /* Synchronize */
462 if ( hashbin->hb_type & HB_LOCK ) {
463 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
464 } /* Default is no-lock */
465
466 /*
467 * Store name and key
468 */
469 entry->q_hash = hashv;
470 if ( name )
471 strlcpy( entry->q_name, name, sizeof(entry->q_name));
472
473 /*
474 * Insert new entry first
475 */
476 enqueue_first( (irda_queue_t**) &hashbin->hb_queue[ bin ],
477 entry);
478 hashbin->hb_size++;
479
480 /* Release lock */
481 if ( hashbin->hb_type & HB_LOCK ) {
482 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
483 } /* Default is no-lock */
484 }
485 EXPORT_SYMBOL(hashbin_insert);
486
487 /*
488 * Function hashbin_remove_first (hashbin)
489 *
490 * Remove first entry of the hashbin
491 *
492 * Note : this function no longer use hashbin_remove(), but does things
493 * similar to hashbin_remove_this(), so can be considered safe.
494 * Jean II
495 */
hashbin_remove_first(hashbin_t * hashbin)496 void *hashbin_remove_first( hashbin_t *hashbin)
497 {
498 unsigned long flags = 0;
499 irda_queue_t *entry = NULL;
500
501 /* Synchronize */
502 if ( hashbin->hb_type & HB_LOCK ) {
503 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
504 } /* Default is no-lock */
505
506 entry = hashbin_get_first( hashbin);
507 if ( entry != NULL) {
508 int bin;
509 long hashv;
510 /*
511 * Locate hashbin
512 */
513 hashv = entry->q_hash;
514 bin = GET_HASHBIN( hashv );
515
516 /*
517 * Dequeue the entry...
518 */
519 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
520 entry);
521 hashbin->hb_size--;
522 entry->q_next = NULL;
523 entry->q_prev = NULL;
524
525 /*
526 * Check if this item is the currently selected item, and in
527 * that case we must reset hb_current
528 */
529 if ( entry == hashbin->hb_current)
530 hashbin->hb_current = NULL;
531 }
532
533 /* Release lock */
534 if ( hashbin->hb_type & HB_LOCK ) {
535 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
536 } /* Default is no-lock */
537
538 return entry;
539 }
540
541
542 /*
543 * Function hashbin_remove (hashbin, hashv, name)
544 *
545 * Remove entry with the given name
546 *
547 * The use of this function is highly discouraged, because the whole
548 * concept behind hashbin_remove() is broken. In many cases, it's not
549 * possible to guarantee the unicity of the index (either hashv or name),
550 * leading to removing the WRONG entry.
551 * The only simple safe use is :
552 * hashbin_remove(hasbin, (int) self, NULL);
553 * In other case, you must think hard to guarantee unicity of the index.
554 * Jean II
555 */
hashbin_remove(hashbin_t * hashbin,long hashv,const char * name)556 void* hashbin_remove( hashbin_t* hashbin, long hashv, const char* name)
557 {
558 int bin, found = FALSE;
559 unsigned long flags = 0;
560 irda_queue_t* entry;
561
562 IRDA_ASSERT( hashbin != NULL, return NULL;);
563 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
564
565 /*
566 * Locate hashbin
567 */
568 if ( name )
569 hashv = hash( name );
570 bin = GET_HASHBIN( hashv );
571
572 /* Synchronize */
573 if ( hashbin->hb_type & HB_LOCK ) {
574 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
575 } /* Default is no-lock */
576
577 /*
578 * Search for entry
579 */
580 entry = hashbin->hb_queue[ bin ];
581 if ( entry ) {
582 do {
583 /*
584 * Check for key
585 */
586 if ( entry->q_hash == hashv ) {
587 /*
588 * Name compare too?
589 */
590 if ( name ) {
591 if ( strcmp( entry->q_name, name) == 0)
592 {
593 found = TRUE;
594 break;
595 }
596 } else {
597 found = TRUE;
598 break;
599 }
600 }
601 entry = entry->q_next;
602 } while ( entry != hashbin->hb_queue[ bin ] );
603 }
604
605 /*
606 * If entry was found, dequeue it
607 */
608 if ( found ) {
609 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
610 entry);
611 hashbin->hb_size--;
612
613 /*
614 * Check if this item is the currently selected item, and in
615 * that case we must reset hb_current
616 */
617 if ( entry == hashbin->hb_current)
618 hashbin->hb_current = NULL;
619 }
620
621 /* Release lock */
622 if ( hashbin->hb_type & HB_LOCK ) {
623 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
624 } /* Default is no-lock */
625
626
627 /* Return */
628 if ( found )
629 return entry;
630 else
631 return NULL;
632
633 }
634 EXPORT_SYMBOL(hashbin_remove);
635
636 /*
637 * Function hashbin_remove_this (hashbin, entry)
638 *
639 * Remove entry with the given name
640 *
641 * In some cases, the user of hashbin can't guarantee the unicity
642 * of either the hashv or name.
643 * In those cases, using the above function is guaranteed to cause troubles,
644 * so we use this one instead...
645 * And by the way, it's also faster, because we skip the search phase ;-)
646 */
hashbin_remove_this(hashbin_t * hashbin,irda_queue_t * entry)647 void* hashbin_remove_this( hashbin_t* hashbin, irda_queue_t* entry)
648 {
649 unsigned long flags = 0;
650 int bin;
651 long hashv;
652
653 IRDA_ASSERT( hashbin != NULL, return NULL;);
654 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
655 IRDA_ASSERT( entry != NULL, return NULL;);
656
657 /* Synchronize */
658 if ( hashbin->hb_type & HB_LOCK ) {
659 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
660 } /* Default is no-lock */
661
662 /* Check if valid and not already removed... */
663 if((entry->q_next == NULL) || (entry->q_prev == NULL)) {
664 entry = NULL;
665 goto out;
666 }
667
668 /*
669 * Locate hashbin
670 */
671 hashv = entry->q_hash;
672 bin = GET_HASHBIN( hashv );
673
674 /*
675 * Dequeue the entry...
676 */
677 dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
678 entry);
679 hashbin->hb_size--;
680 entry->q_next = NULL;
681 entry->q_prev = NULL;
682
683 /*
684 * Check if this item is the currently selected item, and in
685 * that case we must reset hb_current
686 */
687 if ( entry == hashbin->hb_current)
688 hashbin->hb_current = NULL;
689 out:
690 /* Release lock */
691 if ( hashbin->hb_type & HB_LOCK ) {
692 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
693 } /* Default is no-lock */
694
695 return entry;
696 }
697 EXPORT_SYMBOL(hashbin_remove_this);
698
699 /*********************** HASHBIN ENUMERATION ***********************/
700
701 /*
702 * Function hashbin_common_find (hashbin, hashv, name)
703 *
704 * Find item with the given hashv or name
705 *
706 */
hashbin_find(hashbin_t * hashbin,long hashv,const char * name)707 void* hashbin_find( hashbin_t* hashbin, long hashv, const char* name )
708 {
709 int bin;
710 irda_queue_t* entry;
711
712 pr_debug("hashbin_find()\n");
713
714 IRDA_ASSERT( hashbin != NULL, return NULL;);
715 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
716
717 /*
718 * Locate hashbin
719 */
720 if ( name )
721 hashv = hash( name );
722 bin = GET_HASHBIN( hashv );
723
724 /*
725 * Search for entry
726 */
727 entry = hashbin->hb_queue[ bin];
728 if ( entry ) {
729 do {
730 /*
731 * Check for key
732 */
733 if ( entry->q_hash == hashv ) {
734 /*
735 * Name compare too?
736 */
737 if ( name ) {
738 if ( strcmp( entry->q_name, name ) == 0 ) {
739 return entry;
740 }
741 } else {
742 return entry;
743 }
744 }
745 entry = entry->q_next;
746 } while ( entry != hashbin->hb_queue[ bin ] );
747 }
748
749 return NULL;
750 }
751 EXPORT_SYMBOL(hashbin_find);
752
753 /*
754 * Function hashbin_lock_find (hashbin, hashv, name)
755 *
756 * Find item with the given hashv or name
757 *
758 * Same, but with spinlock protection...
759 * I call it safe, but it's only safe with respect to the hashbin, not its
760 * content. - Jean II
761 */
hashbin_lock_find(hashbin_t * hashbin,long hashv,const char * name)762 void* hashbin_lock_find( hashbin_t* hashbin, long hashv, const char* name )
763 {
764 unsigned long flags = 0;
765 irda_queue_t* entry;
766
767 /* Synchronize */
768 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
769
770 /*
771 * Search for entry
772 */
773 entry = hashbin_find(hashbin, hashv, name);
774
775 /* Release lock */
776 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
777
778 return entry;
779 }
780 EXPORT_SYMBOL(hashbin_lock_find);
781
782 /*
783 * Function hashbin_find (hashbin, hashv, name, pnext)
784 *
785 * Find an item with the given hashv or name, and its successor
786 *
787 * This function allow to do concurrent enumerations without the
788 * need to lock over the whole session, because the caller keep the
789 * context of the search. On the other hand, it might fail and return
790 * NULL if the entry is removed. - Jean II
791 */
hashbin_find_next(hashbin_t * hashbin,long hashv,const char * name,void ** pnext)792 void* hashbin_find_next( hashbin_t* hashbin, long hashv, const char* name,
793 void ** pnext)
794 {
795 unsigned long flags = 0;
796 irda_queue_t* entry;
797
798 /* Synchronize */
799 spin_lock_irqsave(&hashbin->hb_spinlock, flags);
800
801 /*
802 * Search for current entry
803 * This allow to check if the current item is still in the
804 * hashbin or has been removed.
805 */
806 entry = hashbin_find(hashbin, hashv, name);
807
808 /*
809 * Trick hashbin_get_next() to return what we want
810 */
811 if(entry) {
812 hashbin->hb_current = entry;
813 *pnext = hashbin_get_next( hashbin );
814 } else
815 *pnext = NULL;
816
817 /* Release lock */
818 spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
819
820 return entry;
821 }
822
823 /*
824 * Function hashbin_get_first (hashbin)
825 *
826 * Get a pointer to first element in hashbin, this function must be
827 * called before any calls to hashbin_get_next()!
828 *
829 */
hashbin_get_first(hashbin_t * hashbin)830 irda_queue_t *hashbin_get_first( hashbin_t* hashbin)
831 {
832 irda_queue_t *entry;
833 int i;
834
835 IRDA_ASSERT( hashbin != NULL, return NULL;);
836 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
837
838 if ( hashbin == NULL)
839 return NULL;
840
841 for ( i = 0; i < HASHBIN_SIZE; i ++ ) {
842 entry = hashbin->hb_queue[ i];
843 if ( entry) {
844 hashbin->hb_current = entry;
845 return entry;
846 }
847 }
848 /*
849 * Did not find any item in hashbin
850 */
851 return NULL;
852 }
853 EXPORT_SYMBOL(hashbin_get_first);
854
855 /*
856 * Function hashbin_get_next (hashbin)
857 *
858 * Get next item in hashbin. A series of hashbin_get_next() calls must
859 * be started by a call to hashbin_get_first(). The function returns
860 * NULL when all items have been traversed
861 *
862 * The context of the search is stored within the hashbin, so you must
863 * protect yourself from concurrent enumerations. - Jean II
864 */
hashbin_get_next(hashbin_t * hashbin)865 irda_queue_t *hashbin_get_next( hashbin_t *hashbin)
866 {
867 irda_queue_t* entry;
868 int bin;
869 int i;
870
871 IRDA_ASSERT( hashbin != NULL, return NULL;);
872 IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
873
874 if ( hashbin->hb_current == NULL) {
875 IRDA_ASSERT( hashbin->hb_current != NULL, return NULL;);
876 return NULL;
877 }
878 entry = hashbin->hb_current->q_next;
879 bin = GET_HASHBIN( entry->q_hash);
880
881 /*
882 * Make sure that we are not back at the beginning of the queue
883 * again
884 */
885 if ( entry != hashbin->hb_queue[ bin ]) {
886 hashbin->hb_current = entry;
887
888 return entry;
889 }
890
891 /*
892 * Check that this is not the last queue in hashbin
893 */
894 if ( bin >= HASHBIN_SIZE)
895 return NULL;
896
897 /*
898 * Move to next queue in hashbin
899 */
900 bin++;
901 for ( i = bin; i < HASHBIN_SIZE; i++ ) {
902 entry = hashbin->hb_queue[ i];
903 if ( entry) {
904 hashbin->hb_current = entry;
905
906 return entry;
907 }
908 }
909 return NULL;
910 }
911 EXPORT_SYMBOL(hashbin_get_next);
912