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.
 */
 
/** @addtogroup sync
 * @{
 */
 
/**
 * @file
 * @brief   Kernel backend for futexes.
 */
 
#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 <proc/task.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.
 * It is also used to serialize access to all futex_t structures.
 * Must be acquired before the task futex B+tree lock.
 */
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;
    futex->refcount = 1;
}
 
/** 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 flags Select mode of operation.
 *
 * @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 flags)
{
    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, flags | SYNCH_FLAGS_INTERRUPTIBLE);
}
 
/** 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 already, 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;
    btree_node_t *leaf;
   
    /*
     * 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);
 
        /*
         * See if the current task knows this futex.
         */
        mutex_lock(&TASK->futexes_lock);
        if (!btree_search(&TASK->futexes, paddr, &leaf)) {
            /*
             * The futex is new to the current task.
             * However, we only have read access.
             * Gain write access and try again.
             */
            mutex_unlock(&TASK->futexes_lock);
            goto gain_write_access;
        }
        mutex_unlock(&TASK->futexes_lock);
 
        rwlock_read_unlock(&futex_ht_lock);
    } else {
gain_write_access:
        /*
         * 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);
           
            /*
             * See if this futex is known to the current task.
             */
            mutex_lock(&TASK->futexes_lock);
            if (!btree_search(&TASK->futexes, paddr, &leaf)) {
                /*
                 * The futex is new to the current task.
                 * Upgrade its reference count and put it to the
                 * current task's B+tree of known futexes.
                 */
                futex->refcount++;
                btree_insert(&TASK->futexes, paddr, futex, leaf);
            }
            mutex_unlock(&TASK->futexes_lock);
   
            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);
           
            /*
             * This is the first task referencing the futex.
             * It can be directly inserted into its
             * B+tree of known futexes.
             */
            mutex_lock(&TASK->futexes_lock);
            btree_insert(&TASK->futexes, paddr, futex, NULL);
            mutex_unlock(&TASK->futexes_lock);
           
            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);
}
 
/** Remove references from futexes known to the current task. */
void futex_cleanup(void)
{
    link_t *cur;
   
    rwlock_write_lock(&futex_ht_lock);
    mutex_lock(&TASK->futexes_lock);
 
    for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) {
        btree_node_t *node;
        int i;
       
        node = list_get_instance(cur, btree_node_t, leaf_link);
        for (i = 0; i < node->keys; i++) {
            futex_t *ftx;
            __address paddr = node->key[i];
           
            ftx = (futex_t *) node->value[i];
            if (--ftx->refcount == 0)
                hash_table_remove(&futex_ht, &paddr, 1);
        }
    }
   
    mutex_unlock(&TASK->futexes_lock);
    rwlock_write_unlock(&futex_ht_lock);
}
 
/** @}
 */
 
 

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/futex.c – Rev 1702 → 1757

Rev 1702		Rev 1757
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	/** @addtogroup sync	29	/** @addtogroup sync
30	* @{	30	* @{
31	*/	31	*/
32		32
33	/**	33	/**
34	* @file	34	* @file
35	* @brief Kernel backend for futexes.	35	* @brief Kernel backend for futexes.
36	*/	36	*/
37		37
38	#include <synch/futex.h>	38	#include <synch/futex.h>
39	#include <synch/rwlock.h>	39	#include <synch/rwlock.h>
40	#include <synch/spinlock.h>	40	#include <synch/spinlock.h>
41	#include <synch/synch.h>	41	#include <synch/synch.h>
42	#include <mm/frame.h>	42	#include <mm/frame.h>
43	#include <mm/page.h>	43	#include <mm/page.h>
44	#include <mm/slab.h>	44	#include <mm/slab.h>
45	#include <proc/thread.h>	45	#include <proc/thread.h>
46	#include <proc/task.h>	46	#include <proc/task.h>
47	#include <genarch/mm/page_pt.h>	47	#include <genarch/mm/page_pt.h>
48	#include <genarch/mm/page_ht.h>	48	#include <genarch/mm/page_ht.h>
49	#include <adt/hash_table.h>	49	#include <adt/hash_table.h>
50	#include <adt/list.h>	50	#include <adt/list.h>
51	#include <arch.h>	51	#include <arch.h>
52	#include <align.h>	52	#include <align.h>
53	#include <panic.h>	53	#include <panic.h>
54	#include <errno.h>	54	#include <errno.h>
55	#include <print.h>	55	#include <print.h>
56		56
57	#define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */	57	#define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */
58		58
59	static void futex_initialize(futex_t *futex);	59	static void futex_initialize(futex_t *futex);
60		60
61	static futex_t *futex_find(__address paddr);	61	static futex_t *futex_find(__address paddr);
62	static index_t futex_ht_hash(__native *key);	62	static index_t futex_ht_hash(__native *key);
63	static bool futex_ht_compare(__native key, count_t keys, link_t item);	63	static bool futex_ht_compare(__native key, count_t keys, link_t item);
64	static void futex_ht_remove_callback(link_t *item);	64	static void futex_ht_remove_callback(link_t *item);
65		65
66	/**	66	/**
67	* Read-write lock protecting global futex hash table.	67	* Read-write lock protecting global futex hash table.
68	* It is also used to serialize access to all futex_t structures.	68	* It is also used to serialize access to all futex_t structures.
69	* Must be acquired before the task futex B+tree lock.	69	* Must be acquired before the task futex B+tree lock.
70	*/	70	*/
71	static rwlock_t futex_ht_lock;	71	static rwlock_t futex_ht_lock;
72		72
73	/** Futex hash table. */	73	/** Futex hash table. */
74	static hash_table_t futex_ht;	74	static hash_table_t futex_ht;
75		75
76	/** Futex hash table operations. */	76	/** Futex hash table operations. */
77	static hash_table_operations_t futex_ht_ops = {	77	static hash_table_operations_t futex_ht_ops = {
78	.hash = futex_ht_hash,	78	.hash = futex_ht_hash,
79	.compare = futex_ht_compare,	79	.compare = futex_ht_compare,
80	.remove_callback = futex_ht_remove_callback	80	.remove_callback = futex_ht_remove_callback
81	};	81	};
82		82
83	/** Initialize futex subsystem. */	83	/** Initialize futex subsystem. */
84	void futex_init(void)	84	void futex_init(void)
85	{	85	{
86	rwlock_initialize(&futex_ht_lock);	86	rwlock_initialize(&futex_ht_lock);
87	hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);	87	hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);
88	}	88	}
89		89
90	/** Initialize kernel futex structure.	90	/** Initialize kernel futex structure.
91	*	91	*
92	* @param futex Kernel futex structure.	92	* @param futex Kernel futex structure.
93	*/	93	*/
94	void futex_initialize(futex_t *futex)	94	void futex_initialize(futex_t *futex)
95	{	95	{
96	waitq_initialize(&futex->wq);	96	waitq_initialize(&futex->wq);
97	link_initialize(&futex->ht_link);	97	link_initialize(&futex->ht_link);
98	futex->paddr = 0;	98	futex->paddr = 0;
99	futex->refcount = 1;	99	futex->refcount = 1;
100	}	100	}
101		101
102	/** Sleep in futex wait queue.	102	/** Sleep in futex wait queue.
103	*	103	*
104	* @param uaddr Userspace address of the futex counter.	104	* @param uaddr Userspace address of the futex counter.
105	* @param usec If non-zero, number of microseconds this thread is willing to sleep.	105	* @param usec If non-zero, number of microseconds this thread is willing to sleep.
106	* @param flags Select mode of operation.	106	* @param flags Select mode of operation.
107	*	107	*
108	* @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.	108	* @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.
109	* If there is no physical mapping for uaddr ENOENT is returned.	109	* If there is no physical mapping for uaddr ENOENT is returned.
110	*/	110	*/
111	__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int flags)	111	__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int flags)
112	{	112	{
113	futex_t *futex;	113	futex_t *futex;
114	__address paddr;	114	__address paddr;
115	pte_t *t;	115	pte_t *t;
116	ipl_t ipl;	116	ipl_t ipl;
117		117
118	ipl = interrupts_disable();	118	ipl = interrupts_disable();
119		119
120	/*	120	/*
121	* Find physical address of futex counter.	121	* Find physical address of futex counter.
122	*/	122	*/
123	page_table_lock(AS, true);	123	page_table_lock(AS, true);
124	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));	124	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
125	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {	125	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {
126	page_table_unlock(AS, true);	126	page_table_unlock(AS, true);
127	interrupts_restore(ipl);	127	interrupts_restore(ipl);
128	return (__native) ENOENT;	128	return (__native) ENOENT;
129	}	129	}
130	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));	130	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
131	page_table_unlock(AS, true);	131	page_table_unlock(AS, true);
132		132
133	interrupts_restore(ipl);	133	interrupts_restore(ipl);
134		134
135	futex = futex_find(paddr);	135	futex = futex_find(paddr);
136		136
137	return (__native) waitq_sleep_timeout(&futex->wq, usec, flags \| SYNCH_FLAGS_INTERRUPTIBLE);	137	return (__native) waitq_sleep_timeout(&futex->wq, usec, flags \| SYNCH_FLAGS_INTERRUPTIBLE);
138	}	138	}
139		139
140	/** Wakeup one thread waiting in futex wait queue.	140	/** Wakeup one thread waiting in futex wait queue.
141	*	141	*
142	* @param uaddr Userspace address of the futex counter.	142	* @param uaddr Userspace address of the futex counter.
143	*	143	*
144	* @return ENOENT if there is no physical mapping for uaddr.	144	* @return ENOENT if there is no physical mapping for uaddr.
145	*/	145	*/
146	__native sys_futex_wakeup(__address uaddr)	146	__native sys_futex_wakeup(__address uaddr)
147	{	147	{
148	futex_t *futex;	148	futex_t *futex;
149	__address paddr;	149	__address paddr;
150	pte_t *t;	150	pte_t *t;
151	ipl_t ipl;	151	ipl_t ipl;
152		152
153	ipl = interrupts_disable();	153	ipl = interrupts_disable();
154		154
155	/*	155	/*
156	* Find physical address of futex counter.	156	* Find physical address of futex counter.
157	*/	157	*/
158	page_table_lock(AS, true);	158	page_table_lock(AS, true);
159	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));	159	t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
160	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {	160	if (!t \|\| !PTE_VALID(t) \|\| !PTE_PRESENT(t)) {
161	page_table_unlock(AS, true);	161	page_table_unlock(AS, true);
162	interrupts_restore(ipl);	162	interrupts_restore(ipl);
163	return (__native) ENOENT;	163	return (__native) ENOENT;
164	}	164	}
165	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));	165	paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
166	page_table_unlock(AS, true);	166	page_table_unlock(AS, true);
167		167
168	interrupts_restore(ipl);	168	interrupts_restore(ipl);
169		169
170	futex = futex_find(paddr);	170	futex = futex_find(paddr);
171		171
172	waitq_wakeup(&futex->wq, WAKEUP_FIRST);	172	waitq_wakeup(&futex->wq, WAKEUP_FIRST);
173		173
174	return 0;	174	return 0;
175	}	175	}
176		176
177	/** Find kernel address of the futex structure corresponding to paddr.	177	/** Find kernel address of the futex structure corresponding to paddr.
178	*	178	*
179	* If the structure does not exist already, a new one is created.	179	* If the structure does not exist already, a new one is created.
180	*	180	*
181	* @param paddr Physical address of the userspace futex counter.	181	* @param paddr Physical address of the userspace futex counter.
182	*	182	*
183	* @return Address of the kernel futex structure.	183	* @return Address of the kernel futex structure.
184	*/	184	*/
185	futex_t *futex_find(__address paddr)	185	futex_t *futex_find(__address paddr)
186	{	186	{
187	link_t *item;	187	link_t *item;
188	futex_t *futex;	188	futex_t *futex;
189	btree_node_t *leaf;	189	btree_node_t *leaf;
190		190
191	/*	191	/*
192	* Find the respective futex structure	192	* Find the respective futex structure
193	* or allocate new one if it does not exist already.	193	* or allocate new one if it does not exist already.
194	*/	194	*/
195	rwlock_read_lock(&futex_ht_lock);	195	rwlock_read_lock(&futex_ht_lock);
196	item = hash_table_find(&futex_ht, &paddr);	196	item = hash_table_find(&futex_ht, &paddr);
197	if (item) {	197	if (item) {
198	futex = hash_table_get_instance(item, futex_t, ht_link);	198	futex = hash_table_get_instance(item, futex_t, ht_link);
199		199
200	/*	200	/*
201	* See if the current task knows this futex.	201	* See if the current task knows this futex.
202	*/	202	*/
203	mutex_lock(&TASK->futexes_lock);	203	mutex_lock(&TASK->futexes_lock);
204	if (!btree_search(&TASK->futexes, paddr, &leaf)) {	204	if (!btree_search(&TASK->futexes, paddr, &leaf)) {
205	/*	205	/*
206	* The futex is new to the current task.	206	* The futex is new to the current task.
207	* However, we only have read access.	207	* However, we only have read access.
208	* Gain write access and try again.	208	* Gain write access and try again.
209	*/	209	*/
210	mutex_unlock(&TASK->futexes_lock);	210	mutex_unlock(&TASK->futexes_lock);
211	goto gain_write_access;	211	goto gain_write_access;
212	}	212	}
213	mutex_unlock(&TASK->futexes_lock);	213	mutex_unlock(&TASK->futexes_lock);
214		214
215	rwlock_read_unlock(&futex_ht_lock);	215	rwlock_read_unlock(&futex_ht_lock);
216	} else {	216	} else {
217	gain_write_access:	217	gain_write_access:
218	/*	218	/*
219	* Upgrade to writer is not currently supported,	219	* Upgrade to writer is not currently supported,
220	* therefore, it is necessary to release the read lock	220	* therefore, it is necessary to release the read lock
221	* and reacquire it as a writer.	221	* and reacquire it as a writer.
222	*/	222	*/
223	rwlock_read_unlock(&futex_ht_lock);	223	rwlock_read_unlock(&futex_ht_lock);
224		224
225	rwlock_write_lock(&futex_ht_lock);	225	rwlock_write_lock(&futex_ht_lock);
226	/*	226	/*
227	* Avoid possible race condition by searching	227	* Avoid possible race condition by searching
228	* the hash table once again with write access.	228	* the hash table once again with write access.
229	*/	229	*/
230	item = hash_table_find(&futex_ht, &paddr);	230	item = hash_table_find(&futex_ht, &paddr);
231	if (item) {	231	if (item) {
232	futex = hash_table_get_instance(item, futex_t, ht_link);	232	futex = hash_table_get_instance(item, futex_t, ht_link);
233		233
234	/*	234	/*
235	* See if this futex is known to the current task.	235	* See if this futex is known to the current task.
236	*/	236	*/
237	mutex_lock(&TASK->futexes_lock);	237	mutex_lock(&TASK->futexes_lock);
238	if (!btree_search(&TASK->futexes, paddr, &leaf)) {	238	if (!btree_search(&TASK->futexes, paddr, &leaf)) {
239	/*	239	/*
240	* The futex is new to the current task.	240	* The futex is new to the current task.
241	* Upgrade its reference count and put it to the	241	* Upgrade its reference count and put it to the
242	* current task's B+tree of known futexes.	242	* current task's B+tree of known futexes.
243	*/	243	*/
244	futex->refcount++;	244	futex->refcount++;
245	btree_insert(&TASK->futexes, paddr, futex, leaf);	245	btree_insert(&TASK->futexes, paddr, futex, leaf);
246	}	246	}
247	mutex_unlock(&TASK->futexes_lock);	247	mutex_unlock(&TASK->futexes_lock);
248		248
249	rwlock_write_unlock(&futex_ht_lock);	249	rwlock_write_unlock(&futex_ht_lock);
250	} else {	250	} else {
251	futex = (futex_t *) malloc(sizeof(futex_t), 0);	251	futex = (futex_t *) malloc(sizeof(futex_t), 0);
252	futex_initialize(futex);	252	futex_initialize(futex);
253	futex->paddr = paddr;	253	futex->paddr = paddr;
254	hash_table_insert(&futex_ht, &paddr, &futex->ht_link);	254	hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
255		255
256	/*	256	/*
257	* This is the first task referencing the futex.	257	* This is the first task referencing the futex.
258	* It can be directly inserted into its	258	* It can be directly inserted into its
259	* B+tree of known futexes.	259	* B+tree of known futexes.
260	*/	260	*/
261	mutex_lock(&TASK->futexes_lock);	261	mutex_lock(&TASK->futexes_lock);
262	btree_insert(&TASK->futexes, paddr, futex, NULL);	262	btree_insert(&TASK->futexes, paddr, futex, NULL);
263	mutex_unlock(&TASK->futexes_lock);	263	mutex_unlock(&TASK->futexes_lock);
264		264
265	rwlock_write_unlock(&futex_ht_lock);	265	rwlock_write_unlock(&futex_ht_lock);
266	}	266	}
267	}	267	}
268		268
269	return futex;	269	return futex;
270	}	270	}
271		271
272	/** Compute hash index into futex hash table.	272	/** Compute hash index into futex hash table.
273	*	273	*
274	* @param key Address where the key (i.e. physical address of futex counter) is stored.	274	* @param key Address where the key (i.e. physical address of futex counter) is stored.
275	*	275	*
276	* @return Index into futex hash table.	276	* @return Index into futex hash table.
277	*/	277	*/
278	index_t futex_ht_hash(__native *key)	278	index_t futex_ht_hash(__native *key)
279	{	279	{
280	return *key & (FUTEX_HT_SIZE-1);	280	return *key & (FUTEX_HT_SIZE-1);
281	}	281	}
282		282
283	/** Compare futex hash table item with a key.	283	/** Compare futex hash table item with a key.
284	*	284	*
285	* @param key Address where the key (i.e. physical address of futex counter) is stored.	285	* @param key Address where the key (i.e. physical address of futex counter) is stored.
286	*	286	*
287	* @return True if the item matches the key. False otherwise.	287	* @return True if the item matches the key. False otherwise.
288	*/	288	*/
289	bool futex_ht_compare(__native key, count_t keys, link_t item)	289	bool futex_ht_compare(__native key, count_t keys, link_t item)
290	{	290	{
291	futex_t *futex;	291	futex_t *futex;
292		292
293	ASSERT(keys == 1);	293	ASSERT(keys == 1);
294		294
295	futex = hash_table_get_instance(item, futex_t, ht_link);	295	futex = hash_table_get_instance(item, futex_t, ht_link);
296	return *key == futex->paddr;	296	return *key == futex->paddr;
297	}	297	}
298		298
299	/** Callback for removal items from futex hash table.	299	/** Callback for removal items from futex hash table.
300	*	300	*
301	* @param item Item removed from the hash table.	301	* @param item Item removed from the hash table.
302	*/	302	*/
303	void futex_ht_remove_callback(link_t *item)	303	void futex_ht_remove_callback(link_t *item)
304	{	304	{
305	futex_t *futex;	305	futex_t *futex;
306		306
307	futex = hash_table_get_instance(item, futex_t, ht_link);	307	futex = hash_table_get_instance(item, futex_t, ht_link);
308	free(futex);	308	free(futex);
309	}	309	}
310		310
311	/** Remove references from futexes known to the current task. */	311	/** Remove references from futexes known to the current task. */
312	void futex_cleanup(void)	312	void futex_cleanup(void)
313	{	313	{
314	link_t *cur;	314	link_t *cur;
315		315
316	rwlock_write_lock(&futex_ht_lock);	316	rwlock_write_lock(&futex_ht_lock);
317	mutex_lock(&TASK->futexes_lock);	317	mutex_lock(&TASK->futexes_lock);
318		318
319	for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) {	319	for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) {
320	btree_node_t *node;	320	btree_node_t *node;
321	int i;	321	int i;
322		322
323	node = list_get_instance(cur, btree_node_t, leaf_link);	323	node = list_get_instance(cur, btree_node_t, leaf_link);
324	for (i = 0; i < node->keys; i++) {	324	for (i = 0; i < node->keys; i++) {
325	futex_t *ftx;	325	futex_t *ftx;
326	__address paddr = node->key[i];	326	__address paddr = node->key[i];
327		327
328	ftx = (futex_t *) node->value[i];	328	ftx = (futex_t *) node->value[i];
329	if (--ftx->refcount == 0)	329	if (--ftx->refcount == 0)
330	hash_table_remove(&futex_ht, &paddr, 1);	330	hash_table_remove(&futex_ht, &paddr, 1);
331	}	331	}
332	}	332	}
333		333
334	mutex_unlock(&TASK->futexes_lock);	334	mutex_unlock(&TASK->futexes_lock);
335	rwlock_write_unlock(&futex_ht_lock);	335	rwlock_write_unlock(&futex_ht_lock);
336	}	336	}
337		337
338	/** @}	338	/** @}
339	*/	339	*/
340		-
341		340