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author | 2005-04-16 15:20:36 -0700 | |
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committer | 2005-04-16 15:20:36 -0700 | |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/irda/irqueue.c | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'net/irda/irqueue.c')
-rw-r--r-- | net/irda/irqueue.c | 915 |
1 files changed, 915 insertions, 0 deletions
diff --git a/net/irda/irqueue.c b/net/irda/irqueue.c new file mode 100644 index 000000000000..b0dd3ea35999 --- /dev/null +++ b/net/irda/irqueue.c @@ -0,0 +1,915 @@ +/********************************************************************* + * + * 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 Tromsø 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 = kmalloc( sizeof(hashbin_t), GFP_ATOMIC); + if (!hashbin) + return NULL; + + /* + * Initialize structure + */ + memset(hashbin, 0, sizeof(hashbin_t)); + 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; +} +EXPORT_SYMBOL(hashbin_find_next); + +/* + * 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); |