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+/*********************************************************************
+ *
+ * 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 Tromsų 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);
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-05 01:39:49 +0000