WebSVN – HelenOS-historic – Diff – /kernel/trunk/generic/src/synch/futex.c


/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
/**
 * @file    futex.c
 * @brief   Kernel backend for futexes.
 *
 * @todo Deallocation of orphaned kernel-side futex structures is not currently implemented.
 */
 
#include <synch/futex.h>
#include <synch/rwlock.h>
#include <synch/spinlock.h>
#include <synch/synch.h>
#include <mm/frame.h>
#include <mm/page.h>
#include <mm/slab.h>
#include <proc/thread.h>
#include <genarch/mm/page_pt.h>
#include <genarch/mm/page_ht.h>
#include <adt/hash_table.h>
#include <adt/list.h>
#include <arch.h>
#include <align.h>
#include <panic.h>
#include <errno.h>
#include <print.h>
 
#define FUTEX_HT_SIZE   1024    /* keep it a power of 2 */
 
static void futex_initialize(futex_t *futex);
 
static futex_t *futex_find(__address paddr);
static index_t futex_ht_hash(__native *key);
static bool futex_ht_compare(__native *key, count_t keys, link_t *item);
static void futex_ht_remove_callback(link_t *item);
 
/** Read-write lock protecting global futex hash table. */
static rwlock_t futex_ht_lock;
 
/** Futex hash table. */
static hash_table_t futex_ht;
 
/** Futex hash table operations. */
static hash_table_operations_t futex_ht_ops = {
    .hash = futex_ht_hash,
    .compare = futex_ht_compare,
    .remove_callback = futex_ht_remove_callback
};
 
/** Initialize futex subsystem. */
void futex_init(void)
{
    rwlock_initialize(&futex_ht_lock);
    hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);
}
 
/** Initialize kernel futex structure.
 *
 * @param futex Kernel futex structure.
 */
void futex_initialize(futex_t *futex)
{
    waitq_initialize(&futex->wq);
    link_initialize(&futex->ht_link);
    futex->paddr = 0;
}
 
/** Sleep in futex wait queue.
 *
 * @param uaddr Userspace address of the futex counter.
 * @param usec If non-zero, number of microseconds this thread is willing to sleep.
 * @param trydown If usec is zero and trydown is non-zero, conditional operation will be attempted.
 *
 * @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.
 *     If there is no physical mapping for uaddr ENOENT is returned.
 */
__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int trydown)
{
    futex_t *futex;
    __address paddr;
    pte_t *t;
    ipl_t ipl;
   
    ipl = interrupts_disable();
 
    /*
     * Find physical address of futex counter.
     */
    page_table_lock(AS, true);
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
        page_table_unlock(AS, true);
        interrupts_restore(ipl);
        return (__native) ENOENT;
    }
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
    page_table_unlock(AS, true);
   
    interrupts_restore(ipl);   
 
    futex = futex_find(paddr);
   
    return (__native) waitq_sleep_timeout(&futex->wq, usec, trydown);
}
 
/** Wakeup one thread waiting in futex wait queue.
 *
 * @param uaddr Userspace address of the futex counter.
 *
 
 * @return ENOENT if there is no physical mapping for uaddr.
 */
__native sys_futex_wakeup(__address uaddr)
{
    futex_t *futex;
    __address paddr;
    pte_t *t;
    ipl_t ipl;
   
    ipl = interrupts_disable();
   
    /*
     * Find physical address of futex counter.
     */
    page_table_lock(AS, true);
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
        page_table_unlock(AS, true);
        interrupts_restore(ipl);
        return (__native) ENOENT;
    }
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
    page_table_unlock(AS, true);
   
    interrupts_restore(ipl);
 
    futex = futex_find(paddr);
       
    waitq_wakeup(&futex->wq, WAKEUP_FIRST);
   
    return 0;
}
 
/** Find kernel address of the futex structure corresponding to paddr.
 *
 * If the structure does not exist alreay, a new one is created.
 *
 * @param paddr Physical address of the userspace futex counter.
 *
 * @return Address of the kernel futex structure.
 */
futex_t *futex_find(__address paddr)
{
    link_t *item;
    futex_t *futex;
   
    /*
     * Find the respective futex structure
     * or allocate new one if it does not exist already.
     */
    rwlock_read_lock(&futex_ht_lock);
    item = hash_table_find(&futex_ht, &paddr);
    if (item) {
        futex = hash_table_get_instance(item, futex_t, ht_link);
        rwlock_read_unlock(&futex_ht_lock);
    } else {
        /*
         * Upgrade to writer is not currently supported,
         * therefore, it is necessary to release the read lock
         * and reacquire it as a writer.
         */
        rwlock_read_unlock(&futex_ht_lock);
 
        rwlock_write_lock(&futex_ht_lock);
        /*
         * Avoid possible race condition by searching
         * the hash table once again with write access.
         */
        item = hash_table_find(&futex_ht, &paddr);
        if (item) {
            futex = hash_table_get_instance(item, futex_t, ht_link);
            rwlock_write_unlock(&futex_ht_lock);
        } else {
            futex = (futex_t *) malloc(sizeof(futex_t), 0);
            futex_initialize(futex);
            futex->paddr = paddr;
            hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
            rwlock_write_unlock(&futex_ht_lock);
        }
    }
   
    return futex;
}
 
/** Compute hash index into futex hash table.
 *
 * @param key Address where the key (i.e. physical address of futex counter) is stored.
 *
 * @return Index into futex hash table.
 */
index_t futex_ht_hash(__native *key)
{
    return *key & (FUTEX_HT_SIZE-1);
}
 
/** Compare futex hash table item with a key.
 *
 * @param key Address where the key (i.e. physical address of futex counter) is stored.
 *
 * @return True if the item matches the key. False otherwise.
 */
bool futex_ht_compare(__native *key, count_t keys, link_t *item)
{
    futex_t *futex;
 
    ASSERT(keys == 1);
 
    futex = hash_table_get_instance(item, futex_t, ht_link);
    return *key == futex->paddr;
}
 
/** Callback for removal items from futex hash table.
 *
 * @param item Item removed from the hash table.
 */
void futex_ht_remove_callback(link_t *item)
{
    futex_t *futex;
 
    futex = hash_table_get_instance(item, futex_t, ht_link);
    free(futex);
}
 

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/futex.c – Rev 1264 → 1414

Rev 1264		Rev 1414
1	/*	1	/*
2	* Copyright (C) 2006 Jakub Jermar	2	* Copyright (C) 2006 Jakub Jermar
3	* All rights reserved.	3	* All rights reserved.
4	*	4	*
5	* Redistribution and use in source and binary forms, with or without	5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions	6	* modification, are permitted provided that the following conditions
7	* are met:	7	* are met:
8	*	8	*
9	* - Redistributions of source code must retain the above copyright	9	* - Redistributions of source code must retain the above copyright
10	* notice, this list of conditions and the following disclaimer.	10	* notice, this list of conditions and the following disclaimer.
11	* - Redistributions in binary form must reproduce the above copyright	11	* - Redistributions in binary form must reproduce the above copyright
12	* notice, this list of conditions and the following disclaimer in the	12	* notice, this list of conditions and the following disclaimer in the
13	* documentation and/or other materials provided with the distribution.	13	* documentation and/or other materials provided with the distribution.
14	* - The name of the author may not be used to endorse or promote products	14	* - The name of the author may not be used to endorse or promote products
15	* derived from this software without specific prior written permission.	15	* derived from this software without specific prior written permission.
16	*	16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR	17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES	18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.	19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,	20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT	21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,	22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY	23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT	24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF	25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.	26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27	*/	27	*/
28		28
29	/**	29	/**
30	* @file futex.c	30	* @file futex.c
31	* @brief Kernel backend for futexes.	31	* @brief Kernel backend for futexes.
32	*	32	*
33	* @todo Deallocation of orphaned kernel-side futex structures is not currently implemented.	33	* @todo Deallocation of orphaned kernel-side futex structures is not currently implemented.
34	*/	34	*/
35		35
36	#include <synch/futex.h>	36	#include <synch/futex.h>
37	#include <synch/rwlock.h>	37	#include <synch/rwlock.h>
38	#include <synch/spinlock.h>	38	#include <synch/spinlock.h>
39	#include <synch/synch.h>	39	#include <synch/synch.h>
40	#include <mm/frame.h>	40	#include <mm/frame.h>
41	#include <mm/page.h>	41	#include <mm/page.h>
42	#include <mm/slab.h>	42	#include <mm/slab.h>
43	#include <proc/thread.h>	43	#include <proc/thread.h>
44	#include <genarch/mm/page_pt.h>	44	#include <genarch/mm/page_pt.h>
45	#include <genarch/mm/page_ht.h>	45	#include <genarch/mm/page_ht.h>
46	#include <adt/hash_table.h>	46	#include <adt/hash_table.h>
47	#include <adt/list.h>	47	#include <adt/list.h>
48	#include <arch.h>	48	#include <arch.h>
49	#include <align.h>	49	#include <align.h>
50	#include <panic.h>	50	#include <panic.h>
51	#include <errno.h>	51	#include <errno.h>
52	#include <print.h>	52	#include <print.h>
53		53
54	#define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */	54	#define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */
55		55
56	static void futex_initialize(futex_t *futex);	56	static void futex_initialize(futex_t *futex);
57		57
58	static futex_t *futex_find(__address paddr);	58	static futex_t *futex_find(__address paddr);
59	static index_t futex_ht_hash(__native *key);	59	static index_t futex_ht_hash(__native *key);
60	static bool futex_ht_compare(__native key, count_t keys, link_t item);	60	static bool futex_ht_compare(__native key, count_t keys, link_t item);
61	static void futex_ht_remove_callback(link_t *item);	61	static void futex_ht_remove_callback(link_t *item);
62		62
63	/** Read-write lock protecting global futex hash table. */	63	/** Read-write lock protecting global futex hash table. */
64	static rwlock_t futex_ht_lock;	64	static rwlock_t futex_ht_lock;
65		65
66	/** Futex hash table. */	66	/** Futex hash table. */
67	static hash_table_t futex_ht;	67	static hash_table_t futex_ht;
68		68
69	/** Futex hash table operations. */	69	/** Futex hash table operations. */
70	static hash_table_operations_t futex_ht_ops = {	70	static hash_table_operations_t futex_ht_ops = {
71	.hash = futex_ht_hash,	71	.hash = futex_ht_hash,
72	.compare = futex_ht_compare,	72	.compare = futex_ht_compare,
73	.remove_callback = futex_ht_remove_callback	73	.remove_callback = futex_ht_remove_callback
74	};	74	};
75		75
76	/** Initialize futex subsystem. */	76	/** Initialize futex subsystem. */
77	void futex_init(void)	77	void futex_init(void)
78	{	78	{
79	rwlock_initialize(&futex_ht_lock);	79	rwlock_initialize(&futex_ht_lock);
80	hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);	80	hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);
81	}	81	}
82		82
83	/** Initialize kernel futex structure.	83	/** Initialize kernel futex structure.
84	*	84	*
85	* @param futex Kernel futex structure.	85	* @param futex Kernel futex structure.
86	*/	86	*/
87	void futex_initialize(futex_t *futex)	87	void futex_initialize(futex_t *futex)
88	{	88	{
89	waitq_initialize(&futex->wq);	89	waitq_initialize(&futex->wq);
90	link_initialize(&futex->ht_link);	90	link_initialize(&futex->ht_link);
91	futex->paddr = 0;	91	futex->paddr = 0;
92	}	92	}
93		93
94	/** Sleep in futex wait queue.	94	/** Sleep in futex wait queue.
95	*	95	*
96	* @param uaddr Userspace address of the futex counter.	96	* @param uaddr Userspace address of the futex counter.
97	* @param usec If non-zero, number of microseconds this thread is willing to sleep.	97	* @param usec If non-zero, number of microseconds this thread is willing to sleep.
98	* @param trydown If usec is zero and trydown is non-zero, conditional operation will be attempted.	98	* @param trydown If usec is zero and trydown is non-zero, conditional operation will be attempted.
99	*	99	*
100	* @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.	100	* @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.
101	* If there is no physical mapping for uaddr ENOENT is returned.	101	* If there is no physical mapping for uaddr ENOENT is returned.
102	*/	102	*/
103	__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int trydown)	103	__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int trydown)
104	{	104	{
105	futex_t *futex;	105	futex_t *futex;
106	__address paddr;	106	__address paddr;
107	pte_t *t;	107	pte_t *t;
108	ipl_t ipl;	108	ipl_t ipl;
109		109
110	ipl = interrupts_disable();	110	ipl = interrupts_disable();
111		111
112	/*	112	/*
113	* Find physical address of futex counter.	113	* Find physical address of futex counter.
114	*/	114	*/
115	page_table_lock(AS, true);	115	page_table_lock(AS, true);
116	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));	116	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
117	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {	117	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {
118	page_table_unlock(AS, true);	118	page_table_unlock(AS, true);
119	interrupts_restore(ipl);	119	interrupts_restore(ipl);
120	return (__native) ENOENT;	120	return (__native) ENOENT;
121	}	121	}
122	paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));	122	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
123	page_table_unlock(AS, true);	123	page_table_unlock(AS, true);
124		124
125	interrupts_restore(ipl);	125	interrupts_restore(ipl);
126		126
127	futex = futex_find(paddr);	127	futex = futex_find(paddr);
128		128
129	return (__native) waitq_sleep_timeout(&futex->wq, usec, trydown);	129	return (__native) waitq_sleep_timeout(&futex->wq, usec, trydown);
130	}	130	}
131		131
132	/** Wakeup one thread waiting in futex wait queue.	132	/** Wakeup one thread waiting in futex wait queue.
133	*	133	*
134	* @param uaddr Userspace address of the futex counter.	134	* @param uaddr Userspace address of the futex counter.
135	*	135	*
136	* @return ENOENT if there is no futex associated with the address	-
137	* or if there is no physical mapping for uaddr.	136	* @return ENOENT if there is no physical mapping for uaddr.
138	*/	137	*/
139	__native sys_futex_wakeup(__address uaddr)	138	__native sys_futex_wakeup(__address uaddr)
140	{	139	{
141	futex_t *futex;	140	futex_t *futex;
142	__address paddr;	141	__address paddr;
143	pte_t *t;	142	pte_t *t;
144	ipl_t ipl;	143	ipl_t ipl;
145		144
146	ipl = interrupts_disable();	145	ipl = interrupts_disable();
147		146
148	/*	147	/*
149	* Find physical address of futex counter.	148	* Find physical address of futex counter.
150	*/	149	*/
151	page_table_lock(AS, true);	150	page_table_lock(AS, true);
152	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));	151	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
153	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {	152	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {
154	page_table_unlock(AS, true);	153	page_table_unlock(AS, true);
155	interrupts_restore(ipl);	154	interrupts_restore(ipl);
156	return (__native) ENOENT;	155	return (__native) ENOENT;
157	}	156	}
158	paddr = PFN2ADDR(PTE_GET_FRAME(t)) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));	157	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
159	page_table_unlock(AS, true);	158	page_table_unlock(AS, true);
160		159
161	interrupts_restore(ipl);	160	interrupts_restore(ipl);
162		161
163	futex = futex_find(paddr);	162	futex = futex_find(paddr);
164		163
165	waitq_wakeup(&futex->wq, WAKEUP_FIRST);	164	waitq_wakeup(&futex->wq, WAKEUP_FIRST);
166		165
167	return 0;	166	return 0;
168	}	167	}
169		168
170	/** Find kernel address of the futex structure corresponding to paddr.	169	/** Find kernel address of the futex structure corresponding to paddr.
171	*	170	*
172	* If the structure does not exist alreay, a new one is created.	171	* If the structure does not exist alreay, a new one is created.
173	*	172	*
174	* @param paddr Physical address of the userspace futex counter.	173	* @param paddr Physical address of the userspace futex counter.
175	*	174	*
176	* @return Address of the kernel futex structure.	175	* @return Address of the kernel futex structure.
177	*/	176	*/
178	futex_t *futex_find(__address paddr)	177	futex_t *futex_find(__address paddr)
179	{	178	{
180	link_t *item;	179	link_t *item;
181	futex_t *futex;	180	futex_t *futex;
182		181
183	/*	182	/*
184	* Find the respective futex structure	183	* Find the respective futex structure
185	* or allocate new one if it does not exist already.	184	* or allocate new one if it does not exist already.
186	*/	185	*/
187	rwlock_read_lock(&futex_ht_lock);	186	rwlock_read_lock(&futex_ht_lock);
188	item = hash_table_find(&futex_ht, &paddr);	187	item = hash_table_find(&futex_ht, &paddr);
189	if (item) {	188	if (item) {
190	futex = hash_table_get_instance(item, futex_t, ht_link);	189	futex = hash_table_get_instance(item, futex_t, ht_link);
191	rwlock_read_unlock(&futex_ht_lock);	190	rwlock_read_unlock(&futex_ht_lock);
192	} else {	191	} else {
193	/*	192	/*
194	* Upgrade to writer is not currently supported,	193	* Upgrade to writer is not currently supported,
195	* Therefore, it is necessary to release the read lock	194	* therefore, it is necessary to release the read lock
196	* and reacquire it as a writer.	195	* and reacquire it as a writer.
197	*/	196	*/
198	rwlock_read_unlock(&futex_ht_lock);	197	rwlock_read_unlock(&futex_ht_lock);
199		198
200	rwlock_write_lock(&futex_ht_lock);	199	rwlock_write_lock(&futex_ht_lock);
201	/*	200	/*
202	* Avoid possible race condition by searching	201	* Avoid possible race condition by searching
203	* the hash table once again with write access.	202	* the hash table once again with write access.
204	*/	203	*/
205	item = hash_table_find(&futex_ht, &paddr);	204	item = hash_table_find(&futex_ht, &paddr);
206	if (item) {	205	if (item) {
207	futex = hash_table_get_instance(item, futex_t, ht_link);	206	futex = hash_table_get_instance(item, futex_t, ht_link);
208	rwlock_write_unlock(&futex_ht_lock);	207	rwlock_write_unlock(&futex_ht_lock);
209	} else {	208	} else {
210	futex = (futex_t *) malloc(sizeof(futex_t), 0);	209	futex = (futex_t *) malloc(sizeof(futex_t), 0);
211	futex_initialize(futex);	210	futex_initialize(futex);
212	futex->paddr = paddr;	211	futex->paddr = paddr;
213	hash_table_insert(&futex_ht, &paddr, &futex->ht_link);	212	hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
214	rwlock_write_unlock(&futex_ht_lock);	213	rwlock_write_unlock(&futex_ht_lock);
215	}	214	}
216	}	215	}
217		216
218	return futex;	217	return futex;
219	}	218	}
220		219
221	/** Compute hash index into futex hash table.	220	/** Compute hash index into futex hash table.
222	*	221	*
223	* @param key Address where the key (i.e. physical address of futex counter) is stored.	222	* @param key Address where the key (i.e. physical address of futex counter) is stored.
224	*	223	*
225	* @return Index into futex hash table.	224	* @return Index into futex hash table.
226	*/	225	*/
227	index_t futex_ht_hash(__native *key)	226	index_t futex_ht_hash(__native *key)
228	{	227	{
229	return *key & (FUTEX_HT_SIZE-1);	228	return *key & (FUTEX_HT_SIZE-1);
230	}	229	}
231		230
232	/** Compare futex hash table item with a key.	231	/** Compare futex hash table item with a key.
233	*	232	*
234	* @param key Address where the key (i.e. physical address of futex counter) is stored.	233	* @param key Address where the key (i.e. physical address of futex counter) is stored.
235	*	234	*
236	* @return True if the item matches the key. False otherwise.	235	* @return True if the item matches the key. False otherwise.
237	*/	236	*/
238	bool futex_ht_compare(__native key, count_t keys, link_t item)	237	bool futex_ht_compare(__native key, count_t keys, link_t item)
239	{	238	{
240	futex_t *futex;	239	futex_t *futex;
241		240
242	ASSERT(keys == 1);	241	ASSERT(keys == 1);
243		242
244	futex = hash_table_get_instance(item, futex_t, ht_link);	243	futex = hash_table_get_instance(item, futex_t, ht_link);
245	return *key == futex->paddr;	244	return *key == futex->paddr;
246	}	245	}
247		246
248	/** Callback for removal items from futex hash table.	247	/** Callback for removal items from futex hash table.
249	*	248	*
250	* @param item Item removed from the hash table.	249	* @param item Item removed from the hash table.
251	*/	250	*/
252	void futex_ht_remove_callback(link_t *item)	251	void futex_ht_remove_callback(link_t *item)
253	{	252	{
254	futex_t *futex;	253	futex_t *futex;
255		254
256	futex = hash_table_get_instance(item, futex_t, ht_link);	255	futex = hash_table_get_instance(item, futex_t, ht_link);
257	free(futex);	256	free(futex);
258	}	257	}
259		258