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- irqueue.c
/*********************************************************************
*
* 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 search, 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 <linux/slab.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", __func__);
/*
* 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.
*/
#ifdef CONFIG_LOCKDEP
static int hashbin_lock_depth = 0;
#endif
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_nested(&hashbin->hb_spinlock, flags,
hashbin_lock_depth++);
}
/*
* 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);
#ifdef CONFIG_LOCKDEP
hashbin_lock_depth--;
#endif
}
/*
* 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", __func__);
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", __func__);
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", __func__);
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 = 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 = 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);