summaryrefslogtreecommitdiff
path: root/net/irda/irqueue.c
blob: 1d26cd33ea13af07bbc22e53df6ce54c02f3e759 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
/*********************************************************************
 *                
 * Filename:      irqueue.c
 * Version:       0.3
 * Description:   General queue implementation
 * Status:        Experimental.
 * Author:        Dag Brattli <dagb@cs.uit.no>
 * Created at:    Tue Jun  9 13:29:31 1998
 * Modified at:   Sun Dec 12 13:48:22 1999
 * Modified by:   Dag Brattli <dagb@cs.uit.no>
 * Modified at:   Thu Jan  4 14:29:10 CET 2001
 * Modified by:   Marc Zyngier <mzyngier@freesurf.fr>
 * 
 *     Copyright (C) 1998-1999, Aage Kvalnes <aage@cs.uit.no>
 *     Copyright (C) 1998, Dag Brattli, 
 *     All Rights Reserved.
 *
 *     This code is taken from the Vortex Operating System written by Aage
 *     Kvalnes. Aage has agreed that this code can use the GPL licence,
 *     although he does not use that licence in his own code.
 *     
 *     This copyright does however _not_ include the ELF hash() function
 *     which I currently don't know which licence or copyright it
 *     has. Please inform me if you know.
 *      
 *     This program is free software; you can redistribute it and/or 
 *     modify it under the terms of the GNU General Public License as 
 *     published by the Free Software Foundation; either version 2 of 
 *     the License, or (at your option) any later version.
 *  
 *     Neither Dag Brattli nor University of Troms� admit liability nor
 *     provide warranty for any of this software. This material is 
 *     provided "AS-IS" and at no charge.
 *     
 ********************************************************************/

/*
 * NOTE :
 * There are various problems with this package :
 *	o the hash function for ints is pathetic (but could be changed)
 *	o locking is sometime suspicious (especially during enumeration)
 *	o most users have only a few elements (== overhead)
 *	o most users never use seach, so don't benefit from hashing
 * Problem already fixed :
 *	o not 64 bit compliant (most users do hashv = (int) self)
 *	o hashbin_remove() is broken => use hashbin_remove_this()
 * I think most users would be better served by a simple linked list
 * (like include/linux/list.h) with a global spinlock per list.
 * Jean II
 */

/*
 * Notes on the concurrent access to hashbin and other SMP issues
 * -------------------------------------------------------------
 *	Hashbins are very often in the IrDA stack a global repository of
 * information, and therefore used in a very asynchronous manner following
 * various events (driver calls, timers, user calls...).
 *	Therefore, very often it is highly important to consider the
 * management of concurrent access to the hashbin and how to guarantee the
 * consistency of the operations on it.
 *
 *	First, we need to define the objective of locking :
 *		1) Protect user data (content pointed by the hashbin)
 *		2) Protect hashbin structure itself (linked list in each bin)
 *
 *			     OLD LOCKING
 *			     -----------
 *
 *	The previous locking strategy, either HB_LOCAL or HB_GLOBAL were
 * both inadequate in *both* aspect.
 *		o HB_GLOBAL was using a spinlock for each bin (local locking).
 *		o HB_LOCAL was disabling irq on *all* CPUs, so use a single
 *		  global semaphore.
 *	The problems were :
 *		A) Global irq disabling is no longer supported by the kernel
 *		B) No protection for the hashbin struct global data
 *			o hashbin_delete()
 *			o hb_current
 *		C) No protection for user data in some cases
 *
 *	A) HB_LOCAL use global irq disabling, so doesn't work on kernel
 * 2.5.X. Even when it is supported (kernel 2.4.X and earlier), its
 * performance is not satisfactory on SMP setups. Most hashbins were
 * HB_LOCAL, so (A) definitely need fixing.
 *	B) HB_LOCAL could be modified to fix (B). However, because HB_GLOBAL
 * lock only the individual bins, it will never be able to lock the
 * global data, so can't do (B).
 *	C) Some functions return pointer to data that is still in the
 * hashbin :
 *		o hashbin_find()
 *		o hashbin_get_first()
 *		o hashbin_get_next()
 *	As the data is still in the hashbin, it may be changed or free'd
 * while the caller is examinimg the data. In those case, locking can't
 * be done within the hashbin, but must include use of the data within
 * the caller.
 *	The caller can easily do this with HB_LOCAL (just disable irqs).
 * However, this is impossible with HB_GLOBAL because the caller has no
 * way to know the proper bin, so don't know which spinlock to use.
 *
 *	Quick summary : can no longer use HB_LOCAL, and HB_GLOBAL is
 * fundamentally broken and will never work.
 *
 *			     NEW LOCKING
 *			     -----------
 *
 *	To fix those problems, I've introduce a few changes in the
 * hashbin locking :
 *		1) New HB_LOCK scheme
 *		2) hashbin->hb_spinlock
 *		3) New hashbin usage policy
 *
 * HB_LOCK :
 * -------
 *	HB_LOCK is a locking scheme intermediate between the old HB_LOCAL
 * and HB_GLOBAL. It uses a single spinlock to protect the whole content
 * of the hashbin. As it is a single spinlock, it can protect the global
 * data of the hashbin and not only the bins themselves.
 *	HB_LOCK can only protect some of the hashbin calls, so it only lock
 * call that can be made 100% safe and leave other call unprotected.
 *	HB_LOCK in theory is slower than HB_GLOBAL, but as the hashbin
 * content is always small contention is not high, so it doesn't matter
 * much. HB_LOCK is probably faster than HB_LOCAL.
 *
 * hashbin->hb_spinlock :
 * --------------------
 *	The spinlock that HB_LOCK uses is available for caller, so that
 * the caller can protect unprotected calls (see below).
 *	If the caller want to do entirely its own locking (HB_NOLOCK), he
 * can do so and may use safely this spinlock.
 *	Locking is done like this :
 *		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
 *	Releasing the lock :
 *		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
 *
 * Safe & Protected calls :
 * ----------------------
 *	The following calls are safe or protected via HB_LOCK :
 *		o hashbin_new()		-> safe
 *		o hashbin_delete()
 *		o hashbin_insert()
 *		o hashbin_remove_first()
 *		o hashbin_remove()
 *		o hashbin_remove_this()
 *		o HASHBIN_GET_SIZE()	-> atomic
 *
 *	The following calls only protect the hashbin itself :
 *		o hashbin_lock_find()
 *		o hashbin_find_next()
 *
 * Unprotected calls :
 * -----------------
 *	The following calls need to be protected by the caller :
 *		o hashbin_find()
 *		o hashbin_get_first()
 *		o hashbin_get_next()
 *
 * Locking Policy :
 * --------------
 *	If the hashbin is used only in a single thread of execution
 * (explicitly or implicitely), you can use HB_NOLOCK
 *	If the calling module already provide concurrent access protection,
 * you may use HB_NOLOCK.
 *
 *	In all other cases, you need to use HB_LOCK and lock the hashbin
 * every time before calling one of the unprotected calls. You also must
 * use the pointer returned by the unprotected call within the locked
 * region.
 *
 * Extra care for enumeration :
 * --------------------------
 *	hashbin_get_first() and hashbin_get_next() use the hashbin to
 * store the current position, in hb_current.
 *	As long as the hashbin remains locked, this is safe. If you unlock
 * the hashbin, the current position may change if anybody else modify
 * or enumerate the hashbin.
 *	Summary : do the full enumeration while locked.
 *
 *	Alternatively, you may use hashbin_find_next(). But, this will
 * be slower, is more complex to use and doesn't protect the hashbin
 * content. So, care is needed here as well.
 *
 * Other issues :
 * ------------
 *	I believe that we are overdoing it by using spin_lock_irqsave()
 * and we should use only spin_lock_bh() or similar. But, I don't have
 * the balls to try it out.
 *	Don't believe that because hashbin are now (somewhat) SMP safe
 * that the rest of the code is. Higher layers tend to be safest,
 * but LAP and LMP would need some serious dedicated love.
 *
 * Jean II
 */
#include <linux/module.h>

#include <net/irda/irda.h>
#include <net/irda/irqueue.h>

/************************ QUEUE SUBROUTINES ************************/

/*
 * Hashbin
 */
#define GET_HASHBIN(x) ( x & HASHBIN_MASK )

/*
 * Function hash (name)
 *
 *    This function hash the input string 'name' using the ELF hash
 *    function for strings.
 */
static __u32 hash( const char* name)
{
	__u32 h = 0;
	__u32 g;
	
	while(*name) {
		h = (h<<4) + *name++;
		if ((g = (h & 0xf0000000)))
			h ^=g>>24;
		h &=~g;
	}
	return h;
}

/*
 * Function enqueue_first (queue, proc)
 *
 *    Insert item first in queue.
 *
 */
static void enqueue_first(irda_queue_t **queue, irda_queue_t* element)
{
	
	IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);

	/*
	 * Check if queue is empty.
	 */
	if ( *queue == NULL ) {
		/*
		 * Queue is empty.  Insert one element into the queue.
		 */
		element->q_next = element->q_prev = *queue = element;
		
	} else {
		/*
		 * Queue is not empty.  Insert element into front of queue.
		 */
		element->q_next          = (*queue);
		(*queue)->q_prev->q_next = element;
		element->q_prev          = (*queue)->q_prev;
		(*queue)->q_prev         = element;
		(*queue)                 = element;
	}
}


/*
 * Function dequeue (queue)
 *
 *    Remove first entry in queue
 *
 */
static irda_queue_t *dequeue_first(irda_queue_t **queue)
{
	irda_queue_t *ret;

	IRDA_DEBUG( 4, "dequeue_first()\n");
	
	/*
	 * Set return value
	 */
	ret =  *queue;
	
	if ( *queue == NULL ) {
		/*
		 * Queue was empty.
		 */
	} else if ( (*queue)->q_next == *queue ) {
		/* 
		 *  Queue only contained a single element. It will now be
		 *  empty.  
		 */
		*queue = NULL;
	} else {
		/*
		 * Queue contained several element.  Remove the first one.
		 */
		(*queue)->q_prev->q_next = (*queue)->q_next;
		(*queue)->q_next->q_prev = (*queue)->q_prev;
		*queue = (*queue)->q_next;
	}
	
	/*
	 * Return the removed entry (or NULL of queue was empty).
	 */
	return ret;
}

/*
 * Function dequeue_general (queue, element)
 *
 *
 */
static irda_queue_t *dequeue_general(irda_queue_t **queue, irda_queue_t* element)
{
	irda_queue_t *ret;
	
	IRDA_DEBUG( 4, "dequeue_general()\n");
	
	/*
	 * Set return value
	 */
	ret =  *queue;
		
	if ( *queue == NULL ) {
		/*
		 * Queue was empty.
		 */
	} else if ( (*queue)->q_next == *queue ) {
		/* 
		 *  Queue only contained a single element. It will now be
		 *  empty.  
		 */
		*queue = NULL;
		
	} else {
		/*
		 *  Remove specific element.
		 */
		element->q_prev->q_next = element->q_next;
		element->q_next->q_prev = element->q_prev;
		if ( (*queue) == element)
			(*queue) = element->q_next;
	}
	
	/*
	 * Return the removed entry (or NULL of queue was empty).
	 */
	return ret;
}

/************************ HASHBIN MANAGEMENT ************************/

/*
 * Function hashbin_create ( type, name )
 *
 *    Create hashbin!
 *
 */
hashbin_t *hashbin_new(int type)
{
	hashbin_t* hashbin;
	
	/*
	 * Allocate new hashbin
	 */
	hashbin = kzalloc(sizeof(*hashbin), GFP_ATOMIC);
	if (!hashbin)
		return NULL;

	/*
	 * Initialize structure
	 */
	hashbin->hb_type = type;
	hashbin->magic = HB_MAGIC;
	//hashbin->hb_current = NULL;

	/* Make sure all spinlock's are unlocked */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_init(&hashbin->hb_spinlock);
	}

	return hashbin;
}
EXPORT_SYMBOL(hashbin_new);


/*
 * Function hashbin_delete (hashbin, free_func)
 *
 *    Destroy hashbin, the free_func can be a user supplied special routine 
 *    for deallocating this structure if it's complex. If not the user can 
 *    just supply kfree, which should take care of the job.
 */
int hashbin_delete( hashbin_t* hashbin, FREE_FUNC free_func)
{
	irda_queue_t* queue;
	unsigned long flags = 0;
	int i;

	IRDA_ASSERT(hashbin != NULL, return -1;);
	IRDA_ASSERT(hashbin->magic == HB_MAGIC, return -1;);
	
	/* Synchronize */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
	}

	/*
	 *  Free the entries in the hashbin, TODO: use hashbin_clear when
	 *  it has been shown to work
	 */
	for (i = 0; i < HASHBIN_SIZE; i ++ ) {
		queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
		while (queue ) {
			if (free_func)
				(*free_func)(queue);
			queue = dequeue_first( 
				(irda_queue_t**) &hashbin->hb_queue[i]);
		}
	}
	
	/* Cleanup local data */
	hashbin->hb_current = NULL;
	hashbin->magic = ~HB_MAGIC;

	/* Release lock */
	if ( hashbin->hb_type & HB_LOCK) {
		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
	}

	/*
	 *  Free the hashbin structure
	 */
	kfree(hashbin);

	return 0;
}
EXPORT_SYMBOL(hashbin_delete);

/********************* HASHBIN LIST OPERATIONS *********************/

/*
 * Function hashbin_insert (hashbin, entry, name)
 *
 *    Insert an entry into the hashbin
 *
 */
void hashbin_insert(hashbin_t* hashbin, irda_queue_t* entry, long hashv, 
		    const char* name)
{
	unsigned long flags = 0;
	int bin;

	IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);

	IRDA_ASSERT( hashbin != NULL, return;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return;);

	/*
	 * Locate hashbin
	 */
	if ( name )
		hashv = hash( name );
	bin = GET_HASHBIN( hashv );

	/* Synchronize */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */
	
	/*
	 * Store name and key
	 */
	entry->q_hash = hashv;
	if ( name )
		strlcpy( entry->q_name, name, sizeof(entry->q_name));
	
	/*
	 * Insert new entry first
	 */
	enqueue_first( (irda_queue_t**) &hashbin->hb_queue[ bin ],
		       entry);
	hashbin->hb_size++;

	/* Release lock */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */
}
EXPORT_SYMBOL(hashbin_insert);

/* 
 *  Function hashbin_remove_first (hashbin)
 *
 *    Remove first entry of the hashbin
 *
 * Note : this function no longer use hashbin_remove(), but does things
 * similar to hashbin_remove_this(), so can be considered safe.
 * Jean II
 */
void *hashbin_remove_first( hashbin_t *hashbin)
{
	unsigned long flags = 0;
	irda_queue_t *entry = NULL;

	/* Synchronize */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */

	entry = hashbin_get_first( hashbin);
	if ( entry != NULL) {
		int	bin;
		long	hashv;
		/*
		 * Locate hashbin
		 */
		hashv = entry->q_hash;
		bin = GET_HASHBIN( hashv );

		/*
		 * Dequeue the entry...
		 */
		dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
				 (irda_queue_t*) entry );
		hashbin->hb_size--;
		entry->q_next = NULL;
		entry->q_prev = NULL;

		/*
		 *  Check if this item is the currently selected item, and in
		 *  that case we must reset hb_current
		 */
		if ( entry == hashbin->hb_current)
			hashbin->hb_current = NULL;
	}

	/* Release lock */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */

	return entry;
}


/* 
 *  Function hashbin_remove (hashbin, hashv, name)
 *
 *    Remove entry with the given name
 *
 *  The use of this function is highly discouraged, because the whole
 *  concept behind hashbin_remove() is broken. In many cases, it's not
 *  possible to guarantee the unicity of the index (either hashv or name),
 *  leading to removing the WRONG entry.
 *  The only simple safe use is :
 *		hashbin_remove(hasbin, (int) self, NULL);
 *  In other case, you must think hard to guarantee unicity of the index.
 *  Jean II
 */
void* hashbin_remove( hashbin_t* hashbin, long hashv, const char* name)
{
	int bin, found = FALSE;
	unsigned long flags = 0;
	irda_queue_t* entry;

	IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);

	IRDA_ASSERT( hashbin != NULL, return NULL;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
	
	/*
	 * Locate hashbin
	 */
	if ( name )
		hashv = hash( name );
	bin = GET_HASHBIN( hashv );

	/* Synchronize */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */

	/*
	 * Search for entry
	 */
	entry = hashbin->hb_queue[ bin ];
	if ( entry ) {
		do {
			/*
			 * Check for key
			 */
			if ( entry->q_hash == hashv ) {
				/*
				 * Name compare too?
				 */
				if ( name ) {
					if ( strcmp( entry->q_name, name) == 0)
					{
						found = TRUE;
						break;
					}
				} else {
					found = TRUE;
					break;
				}
			}
			entry = entry->q_next;
		} while ( entry != hashbin->hb_queue[ bin ] );
	}
	
	/*
	 * If entry was found, dequeue it
	 */
	if ( found ) {
		dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
				 (irda_queue_t*) entry );
		hashbin->hb_size--;

		/*
		 *  Check if this item is the currently selected item, and in
		 *  that case we must reset hb_current
		 */
		if ( entry == hashbin->hb_current)
			hashbin->hb_current = NULL;
	}

	/* Release lock */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */
       
	
	/* Return */
	if ( found ) 
		return entry;
	else
		return NULL;
	
}
EXPORT_SYMBOL(hashbin_remove);

/* 
 *  Function hashbin_remove_this (hashbin, entry)
 *
 *    Remove entry with the given name
 *
 * In some cases, the user of hashbin can't guarantee the unicity
 * of either the hashv or name.
 * In those cases, using the above function is guaranteed to cause troubles,
 * so we use this one instead...
 * And by the way, it's also faster, because we skip the search phase ;-)
 */
void* hashbin_remove_this( hashbin_t* hashbin, irda_queue_t* entry)
{
	unsigned long flags = 0;
	int	bin;
	long	hashv;

	IRDA_DEBUG( 4, "%s()\n", __FUNCTION__);

	IRDA_ASSERT( hashbin != NULL, return NULL;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);
	IRDA_ASSERT( entry != NULL, return NULL;);
	
	/* Synchronize */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_lock_irqsave(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */

	/* Check if valid and not already removed... */
	if((entry->q_next == NULL) || (entry->q_prev == NULL)) {
		entry = NULL;
		goto out;
	}

	/*
	 * Locate hashbin
	 */
	hashv = entry->q_hash;
	bin = GET_HASHBIN( hashv );

	/*
	 * Dequeue the entry...
	 */
	dequeue_general( (irda_queue_t**) &hashbin->hb_queue[ bin ],
			 (irda_queue_t*) entry );
	hashbin->hb_size--;
	entry->q_next = NULL;
	entry->q_prev = NULL;

	/*
	 *  Check if this item is the currently selected item, and in
	 *  that case we must reset hb_current
	 */
	if ( entry == hashbin->hb_current)
		hashbin->hb_current = NULL;
out:
	/* Release lock */
	if ( hashbin->hb_type & HB_LOCK ) {
		spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
	} /* Default is no-lock  */

	return entry;
}
EXPORT_SYMBOL(hashbin_remove_this);

/*********************** HASHBIN ENUMERATION ***********************/

/*
 * Function hashbin_common_find (hashbin, hashv, name)
 *
 *    Find item with the given hashv or name
 *
 */
void* hashbin_find( hashbin_t* hashbin, long hashv, const char* name )
{
	int bin;
	irda_queue_t* entry;

	IRDA_DEBUG( 4, "hashbin_find()\n");

	IRDA_ASSERT( hashbin != NULL, return NULL;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);

	/*
	 * Locate hashbin
	 */
	if ( name )
		hashv = hash( name );
	bin = GET_HASHBIN( hashv );
	
	/*
	 * Search for entry
	 */
	entry = hashbin->hb_queue[ bin];
	if ( entry ) {
		do {
			/*
			 * Check for key
			 */
			if ( entry->q_hash == hashv ) {
				/*
				 * Name compare too?
				 */
				if ( name ) {
					if ( strcmp( entry->q_name, name ) == 0 ) {
						return entry;
					}
				} else {
					return entry;
				}
			}
			entry = entry->q_next;
		} while ( entry != hashbin->hb_queue[ bin ] );
	}

	return NULL;
}
EXPORT_SYMBOL(hashbin_find);

/*
 * Function hashbin_lock_find (hashbin, hashv, name)
 *
 *    Find item with the given hashv or name
 *
 * Same, but with spinlock protection...
 * I call it safe, but it's only safe with respect to the hashbin, not its
 * content. - Jean II
 */
void* hashbin_lock_find( hashbin_t* hashbin, long hashv, const char* name )
{
	unsigned long flags = 0;
	irda_queue_t* entry;

	/* Synchronize */
	spin_lock_irqsave(&hashbin->hb_spinlock, flags);

	/*
	 * Search for entry
	 */
	entry = (irda_queue_t* ) hashbin_find( hashbin, hashv, name );

	/* Release lock */
	spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);

	return entry;
}
EXPORT_SYMBOL(hashbin_lock_find);

/*
 * Function hashbin_find (hashbin, hashv, name, pnext)
 *
 *    Find an item with the given hashv or name, and its successor
 *
 * This function allow to do concurrent enumerations without the
 * need to lock over the whole session, because the caller keep the
 * context of the search. On the other hand, it might fail and return
 * NULL if the entry is removed. - Jean II
 */
void* hashbin_find_next( hashbin_t* hashbin, long hashv, const char* name,
			 void ** pnext)
{
	unsigned long flags = 0;
	irda_queue_t* entry;

	/* Synchronize */
	spin_lock_irqsave(&hashbin->hb_spinlock, flags);

	/*
	 * Search for current entry
	 * This allow to check if the current item is still in the
	 * hashbin or has been removed.
	 */
	entry = (irda_queue_t* ) hashbin_find( hashbin, hashv, name );

	/*
	 * Trick hashbin_get_next() to return what we want
	 */
	if(entry) {
		hashbin->hb_current = entry;
		*pnext = hashbin_get_next( hashbin );
	} else
		*pnext = NULL;

	/* Release lock */
	spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);

	return entry;
}

/*
 * Function hashbin_get_first (hashbin)
 *
 *    Get a pointer to first element in hashbin, this function must be
 *    called before any calls to hashbin_get_next()!
 *
 */
irda_queue_t *hashbin_get_first( hashbin_t* hashbin) 
{
	irda_queue_t *entry;
	int i;

	IRDA_ASSERT( hashbin != NULL, return NULL;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);

	if ( hashbin == NULL)
		return NULL;

	for ( i = 0; i < HASHBIN_SIZE; i ++ ) {
		entry = hashbin->hb_queue[ i];
		if ( entry) {
			hashbin->hb_current = entry;
			return entry;
		}
	}
	/*
	 *  Did not find any item in hashbin
	 */
	return NULL;
}
EXPORT_SYMBOL(hashbin_get_first);

/*
 * Function hashbin_get_next (hashbin)
 *
 *    Get next item in hashbin. A series of hashbin_get_next() calls must
 *    be started by a call to hashbin_get_first(). The function returns
 *    NULL when all items have been traversed
 * 
 * The context of the search is stored within the hashbin, so you must
 * protect yourself from concurrent enumerations. - Jean II
 */
irda_queue_t *hashbin_get_next( hashbin_t *hashbin)
{
	irda_queue_t* entry;
	int bin;
	int i;

	IRDA_ASSERT( hashbin != NULL, return NULL;);
	IRDA_ASSERT( hashbin->magic == HB_MAGIC, return NULL;);

	if ( hashbin->hb_current == NULL) {
		IRDA_ASSERT( hashbin->hb_current != NULL, return NULL;);
		return NULL;
	}	
	entry = hashbin->hb_current->q_next;
	bin = GET_HASHBIN( entry->q_hash);

	/*  
	 *  Make sure that we are not back at the beginning of the queue
	 *  again 
	 */
	if ( entry != hashbin->hb_queue[ bin ]) {
		hashbin->hb_current = entry;

		return entry;
	}

	/*
	 *  Check that this is not the last queue in hashbin
	 */
	if ( bin >= HASHBIN_SIZE)
		return NULL;
	
	/*
	 *  Move to next queue in hashbin
	 */
	bin++;
	for ( i = bin; i < HASHBIN_SIZE; i++ ) {
		entry = hashbin->hb_queue[ i];
		if ( entry) {
			hashbin->hb_current = entry;
			
			return entry;
		}
	}
	return NULL;
}
EXPORT_SYMBOL(hashbin_get_next);