linux/net/irda/irqueue.c
David S. Miller 4c03b862b1 irda: Fix lockdep annotations in hashbin_delete().
A nested lock depth was added to the hasbin_delete() code but it
doesn't actually work some well and results in tons of lockdep splats.

Fix the code instead to properly drop the lock around the operation
and just keep peeking the head of the hashbin queue.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-02-17 16:19:39 -05:00

912 lines
22 KiB
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)
{
/*
* 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;
pr_debug("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;
pr_debug("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 ++ ) {
while (1) {
queue = dequeue_first((irda_queue_t**) &hashbin->hb_queue[i]);
if (!queue)
break;
if (free_func) {
if (hashbin->hb_type & HB_LOCK)
spin_unlock_irqrestore(&hashbin->hb_spinlock, flags);
free_func(queue);
if (hashbin->hb_type & HB_LOCK)
spin_lock_irqsave(&hashbin->hb_spinlock, flags);
}
}
}
/* 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_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 ],
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_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 ],
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_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 ],
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;
pr_debug("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);