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1109 jermar 1
/*
2071 jermar 2
 * Copyright (c) 2006 Jakub Jermar
1109 jermar 3
 * All rights reserved.
4
 *
5
 * Redistribution and use in source and binary forms, with or without
6
 * modification, are permitted provided that the following conditions
7
 * are met:
8
 *
9
 * - Redistributions of source code must retain the above copyright
10
 *   notice, this list of conditions and the following disclaimer.
11
 * - Redistributions in binary form must reproduce the above copyright
12
 *   notice, this list of conditions and the following disclaimer in the
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
15
 *   derived from this software without specific prior written permission.
16
 *
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
19
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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
26
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
 */
28
 
1757 jermar 29
/** @addtogroup sync
1702 cejka 30
 * @{
31
 */
32
 
1109 jermar 33
/**
1702 cejka 34
 * @file
1264 jermar 35
 * @brief   Kernel backend for futexes.
1109 jermar 36
 */
37
 
38
#include <synch/futex.h>
39
#include <synch/rwlock.h>
1117 jermar 40
#include <synch/spinlock.h>
1109 jermar 41
#include <synch/synch.h>
42
#include <mm/frame.h>
43
#include <mm/page.h>
44
#include <mm/slab.h>
1117 jermar 45
#include <proc/thread.h>
1460 jermar 46
#include <proc/task.h>
1109 jermar 47
#include <genarch/mm/page_pt.h>
48
#include <genarch/mm/page_ht.h>
49
#include <adt/hash_table.h>
50
#include <adt/list.h>
51
#include <arch.h>
52
#include <align.h>
53
#include <panic.h>
54
#include <errno.h>
55
#include <print.h>
56
 
57
#define FUTEX_HT_SIZE   1024    /* keep it a power of 2 */
58
 
59
static void futex_initialize(futex_t *futex);
60
 
1780 jermar 61
static futex_t *futex_find(uintptr_t paddr);
62
static index_t futex_ht_hash(unative_t *key);
63
static bool futex_ht_compare(unative_t *key, count_t keys, link_t *item);
1109 jermar 64
static void futex_ht_remove_callback(link_t *item);
65
 
1460 jermar 66
/**
67
 * Read-write lock protecting global futex hash table.
68
 * It is also used to serialize access to all futex_t structures.
69
 * Must be acquired before the task futex B+tree lock.
70
 */
1109 jermar 71
static rwlock_t futex_ht_lock;
72
 
73
/** Futex hash table. */
74
static hash_table_t futex_ht;
75
 
76
/** Futex hash table operations. */
77
static hash_table_operations_t futex_ht_ops = {
78
    .hash = futex_ht_hash,
79
    .compare = futex_ht_compare,
80
    .remove_callback = futex_ht_remove_callback
81
};
82
 
83
/** Initialize futex subsystem. */
84
void futex_init(void)
85
{
86
    rwlock_initialize(&futex_ht_lock);
87
    hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);
88
}
89
 
90
/** Initialize kernel futex structure.
91
 *
92
 * @param futex Kernel futex structure.
93
 */
94
void futex_initialize(futex_t *futex)
95
{
96
    waitq_initialize(&futex->wq);
97
    link_initialize(&futex->ht_link);
98
    futex->paddr = 0;
1460 jermar 99
    futex->refcount = 1;
1109 jermar 100
}
101
 
102
/** Sleep in futex wait queue.
103
 *
104
 * @param uaddr Userspace address of the futex counter.
2087 jermar 105
 * @param usec If non-zero, number of microseconds this thread is willing to
106
 *     sleep.
1502 jermar 107
 * @param flags Select mode of operation.
1109 jermar 108
 *
2087 jermar 109
 * @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See
110
 *     synch.h. If there is no physical mapping for uaddr ENOENT is returned.
1109 jermar 111
 */
1780 jermar 112
unative_t sys_futex_sleep_timeout(uintptr_t uaddr, uint32_t usec, int flags)
1109 jermar 113
{
114
    futex_t *futex;
1780 jermar 115
    uintptr_t paddr;
1109 jermar 116
    pte_t *t;
1117 jermar 117
    ipl_t ipl;
1109 jermar 118
 
1117 jermar 119
    ipl = interrupts_disable();
120
 
1109 jermar 121
    /*
122
     * Find physical address of futex counter.
123
     */
124
    page_table_lock(AS, true);
125
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
126
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
127
        page_table_unlock(AS, true);
1117 jermar 128
        interrupts_restore(ipl);
1780 jermar 129
        return (unative_t) ENOENT;
1109 jermar 130
    }
1414 jermar 131
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 132
    page_table_unlock(AS, true);
133
 
1117 jermar 134
    interrupts_restore(ipl);   
135
 
1153 jermar 136
    futex = futex_find(paddr);
1109 jermar 137
 
2087 jermar 138
    return (unative_t) waitq_sleep_timeout(&futex->wq, usec, flags |
139
        SYNCH_FLAGS_INTERRUPTIBLE);
1109 jermar 140
}
141
 
142
/** Wakeup one thread waiting in futex wait queue.
143
 *
144
 * @param uaddr Userspace address of the futex counter.
145
 *
1414 jermar 146
 * @return ENOENT if there is no physical mapping for uaddr.
1109 jermar 147
 */
1780 jermar 148
unative_t sys_futex_wakeup(uintptr_t uaddr)
1109 jermar 149
{
1153 jermar 150
    futex_t *futex;
1780 jermar 151
    uintptr_t paddr;
1109 jermar 152
    pte_t *t;
1117 jermar 153
    ipl_t ipl;
1109 jermar 154
 
1117 jermar 155
    ipl = interrupts_disable();
156
 
1109 jermar 157
    /*
158
     * Find physical address of futex counter.
159
     */
160
    page_table_lock(AS, true);
161
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
162
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
163
        page_table_unlock(AS, true);
1117 jermar 164
        interrupts_restore(ipl);
1780 jermar 165
        return (unative_t) ENOENT;
1109 jermar 166
    }
1414 jermar 167
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 168
    page_table_unlock(AS, true);
169
 
1117 jermar 170
    interrupts_restore(ipl);
171
 
1153 jermar 172
    futex = futex_find(paddr);
173
 
174
    waitq_wakeup(&futex->wq, WAKEUP_FIRST);
175
 
176
    return 0;
177
}
178
 
179
/** Find kernel address of the futex structure corresponding to paddr.
180
 *
1460 jermar 181
 * If the structure does not exist already, a new one is created.
1153 jermar 182
 *
183
 * @param paddr Physical address of the userspace futex counter.
184
 *
185
 * @return Address of the kernel futex structure.
186
 */
1780 jermar 187
futex_t *futex_find(uintptr_t paddr)
1153 jermar 188
{
189
    link_t *item;
190
    futex_t *futex;
1460 jermar 191
    btree_node_t *leaf;
1153 jermar 192
 
1109 jermar 193
    /*
1153 jermar 194
     * Find the respective futex structure
195
     * or allocate new one if it does not exist already.
1109 jermar 196
     */
197
    rwlock_read_lock(&futex_ht_lock);
198
    item = hash_table_find(&futex_ht, &paddr);
199
    if (item) {
200
        futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 201
 
202
        /*
203
         * See if the current task knows this futex.
204
         */
205
        mutex_lock(&TASK->futexes_lock);
206
        if (!btree_search(&TASK->futexes, paddr, &leaf)) {
207
            /*
208
             * The futex is new to the current task.
209
             * However, we only have read access.
210
             * Gain write access and try again.
211
             */
212
            mutex_unlock(&TASK->futexes_lock);
213
            goto gain_write_access;
214
        }
215
        mutex_unlock(&TASK->futexes_lock);
216
 
1153 jermar 217
        rwlock_read_unlock(&futex_ht_lock);
218
    } else {
1460 jermar 219
gain_write_access:
1153 jermar 220
        /*
221
         * Upgrade to writer is not currently supported,
1414 jermar 222
         * therefore, it is necessary to release the read lock
1153 jermar 223
         * and reacquire it as a writer.
224
         */
225
        rwlock_read_unlock(&futex_ht_lock);
226
 
227
        rwlock_write_lock(&futex_ht_lock);
228
        /*
229
         * Avoid possible race condition by searching
230
         * the hash table once again with write access.
231
         */
232
        item = hash_table_find(&futex_ht, &paddr);
233
        if (item) {
234
            futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 235
 
236
            /*
237
             * See if this futex is known to the current task.
238
             */
239
            mutex_lock(&TASK->futexes_lock);
240
            if (!btree_search(&TASK->futexes, paddr, &leaf)) {
241
                /*
242
                 * The futex is new to the current task.
243
                 * Upgrade its reference count and put it to the
244
                 * current task's B+tree of known futexes.
245
                 */
246
                futex->refcount++;
2087 jermar 247
                btree_insert(&TASK->futexes, paddr, futex,
248
                    leaf);
1460 jermar 249
            }
250
            mutex_unlock(&TASK->futexes_lock);
251
 
1153 jermar 252
            rwlock_write_unlock(&futex_ht_lock);
253
        } else {
254
            futex = (futex_t *) malloc(sizeof(futex_t), 0);
255
            futex_initialize(futex);
256
            futex->paddr = paddr;
257
            hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
1460 jermar 258
 
259
            /*
260
             * This is the first task referencing the futex.
261
             * It can be directly inserted into its
262
             * B+tree of known futexes.
263
             */
264
            mutex_lock(&TASK->futexes_lock);
265
            btree_insert(&TASK->futexes, paddr, futex, NULL);
266
            mutex_unlock(&TASK->futexes_lock);
267
 
1153 jermar 268
            rwlock_write_unlock(&futex_ht_lock);
269
        }
1109 jermar 270
    }
271
 
1153 jermar 272
    return futex;
1109 jermar 273
}
274
 
275
/** Compute hash index into futex hash table.
276
 *
2087 jermar 277
 * @param key Address where the key (i.e. physical address of futex counter) is
278
 *     stored.
1109 jermar 279
 *
280
 * @return Index into futex hash table.
281
 */
1780 jermar 282
index_t futex_ht_hash(unative_t *key)
1109 jermar 283
{
284
    return *key & (FUTEX_HT_SIZE-1);
285
}
286
 
287
/** Compare futex hash table item with a key.
288
 *
2087 jermar 289
 * @param key Address where the key (i.e. physical address of futex counter) is
290
 *     stored.
1109 jermar 291
 *
1248 jermar 292
 * @return True if the item matches the key. False otherwise.
1109 jermar 293
 */
1780 jermar 294
bool futex_ht_compare(unative_t *key, count_t keys, link_t *item)
1109 jermar 295
{
296
    futex_t *futex;
297
 
298
    ASSERT(keys == 1);
299
 
300
    futex = hash_table_get_instance(item, futex_t, ht_link);
301
    return *key == futex->paddr;
302
}
303
 
304
/** Callback for removal items from futex hash table.
305
 *
306
 * @param item Item removed from the hash table.
307
 */
308
void futex_ht_remove_callback(link_t *item)
309
{
310
    futex_t *futex;
311
 
312
    futex = hash_table_get_instance(item, futex_t, ht_link);
313
    free(futex);
314
}
1583 jermar 315
 
316
/** Remove references from futexes known to the current task. */
317
void futex_cleanup(void)
318
{
1586 jermar 319
    link_t *cur;
320
 
321
    rwlock_write_lock(&futex_ht_lock);
322
    mutex_lock(&TASK->futexes_lock);
323
 
2087 jermar 324
    for (cur = TASK->futexes.leaf_head.next;
325
        cur != &TASK->futexes.leaf_head; cur = cur->next) {
1586 jermar 326
        btree_node_t *node;
327
        int i;
328
 
329
        node = list_get_instance(cur, btree_node_t, leaf_link);
330
        for (i = 0; i < node->keys; i++) {
331
            futex_t *ftx;
1780 jermar 332
            uintptr_t paddr = node->key[i];
1586 jermar 333
 
334
            ftx = (futex_t *) node->value[i];
335
            if (--ftx->refcount == 0)
336
                hash_table_remove(&futex_ht, &paddr, 1);
337
        }
338
    }
339
 
340
    mutex_unlock(&TASK->futexes_lock);
341
    rwlock_write_unlock(&futex_ht_lock);
1583 jermar 342
}
1702 cejka 343
 
1757 jermar 344
/** @}
1702 cejka 345
 */