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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
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
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);
4490 decky 62
static size_t futex_ht_hash(unative_t *key);
63
static bool futex_ht_compare(unative_t *key, size_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;
3603 svoboda 118
    int rc;
1109 jermar 119
 
1117 jermar 120
    ipl = interrupts_disable();
121
 
1109 jermar 122
    /*
123
     * Find physical address of futex counter.
124
     */
125
    page_table_lock(AS, true);
126
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
127
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
128
        page_table_unlock(AS, true);
1117 jermar 129
        interrupts_restore(ipl);
1780 jermar 130
        return (unative_t) ENOENT;
1109 jermar 131
    }
1414 jermar 132
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 133
    page_table_unlock(AS, true);
134
 
1117 jermar 135
    interrupts_restore(ipl);   
136
 
1153 jermar 137
    futex = futex_find(paddr);
3603 svoboda 138
 
139
#ifdef CONFIG_UDEBUG
140
    udebug_stoppable_begin();
141
#endif
142
    rc = waitq_sleep_timeout(&futex->wq, usec, flags |
2087 jermar 143
        SYNCH_FLAGS_INTERRUPTIBLE);
3603 svoboda 144
 
145
#ifdef CONFIG_UDEBUG
146
    udebug_stoppable_end();
147
#endif
148
    return (unative_t) rc;
1109 jermar 149
}
150
 
151
/** Wakeup one thread waiting in futex wait queue.
152
 *
153
 * @param uaddr Userspace address of the futex counter.
154
 *
1414 jermar 155
 * @return ENOENT if there is no physical mapping for uaddr.
1109 jermar 156
 */
1780 jermar 157
unative_t sys_futex_wakeup(uintptr_t uaddr)
1109 jermar 158
{
1153 jermar 159
    futex_t *futex;
1780 jermar 160
    uintptr_t paddr;
1109 jermar 161
    pte_t *t;
1117 jermar 162
    ipl_t ipl;
1109 jermar 163
 
1117 jermar 164
    ipl = interrupts_disable();
165
 
1109 jermar 166
    /*
167
     * Find physical address of futex counter.
168
     */
169
    page_table_lock(AS, true);
170
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
171
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
172
        page_table_unlock(AS, true);
1117 jermar 173
        interrupts_restore(ipl);
1780 jermar 174
        return (unative_t) ENOENT;
1109 jermar 175
    }
1414 jermar 176
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 177
    page_table_unlock(AS, true);
178
 
1117 jermar 179
    interrupts_restore(ipl);
180
 
1153 jermar 181
    futex = futex_find(paddr);
182
 
183
    waitq_wakeup(&futex->wq, WAKEUP_FIRST);
184
 
185
    return 0;
186
}
187
 
188
/** Find kernel address of the futex structure corresponding to paddr.
189
 *
1460 jermar 190
 * If the structure does not exist already, a new one is created.
1153 jermar 191
 *
192
 * @param paddr Physical address of the userspace futex counter.
193
 *
194
 * @return Address of the kernel futex structure.
195
 */
1780 jermar 196
futex_t *futex_find(uintptr_t paddr)
1153 jermar 197
{
198
    link_t *item;
199
    futex_t *futex;
1460 jermar 200
    btree_node_t *leaf;
1153 jermar 201
 
1109 jermar 202
    /*
1153 jermar 203
     * Find the respective futex structure
204
     * or allocate new one if it does not exist already.
1109 jermar 205
     */
206
    rwlock_read_lock(&futex_ht_lock);
207
    item = hash_table_find(&futex_ht, &paddr);
208
    if (item) {
209
        futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 210
 
211
        /*
212
         * See if the current task knows this futex.
213
         */
214
        mutex_lock(&TASK->futexes_lock);
215
        if (!btree_search(&TASK->futexes, paddr, &leaf)) {
216
            /*
217
             * The futex is new to the current task.
218
             * However, we only have read access.
219
             * Gain write access and try again.
220
             */
221
            mutex_unlock(&TASK->futexes_lock);
222
            goto gain_write_access;
223
        }
224
        mutex_unlock(&TASK->futexes_lock);
225
 
1153 jermar 226
        rwlock_read_unlock(&futex_ht_lock);
227
    } else {
1460 jermar 228
gain_write_access:
1153 jermar 229
        /*
230
         * Upgrade to writer is not currently supported,
1414 jermar 231
         * therefore, it is necessary to release the read lock
1153 jermar 232
         * and reacquire it as a writer.
233
         */
234
        rwlock_read_unlock(&futex_ht_lock);
235
 
236
        rwlock_write_lock(&futex_ht_lock);
237
        /*
238
         * Avoid possible race condition by searching
239
         * the hash table once again with write access.
240
         */
241
        item = hash_table_find(&futex_ht, &paddr);
242
        if (item) {
243
            futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 244
 
245
            /*
246
             * See if this futex is known to the current task.
247
             */
248
            mutex_lock(&TASK->futexes_lock);
249
            if (!btree_search(&TASK->futexes, paddr, &leaf)) {
250
                /*
251
                 * The futex is new to the current task.
252
                 * Upgrade its reference count and put it to the
253
                 * current task's B+tree of known futexes.
254
                 */
255
                futex->refcount++;
2087 jermar 256
                btree_insert(&TASK->futexes, paddr, futex,
257
                    leaf);
1460 jermar 258
            }
259
            mutex_unlock(&TASK->futexes_lock);
260
 
1153 jermar 261
            rwlock_write_unlock(&futex_ht_lock);
262
        } else {
263
            futex = (futex_t *) malloc(sizeof(futex_t), 0);
264
            futex_initialize(futex);
265
            futex->paddr = paddr;
266
            hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
1460 jermar 267
 
268
            /*
269
             * This is the first task referencing the futex.
270
             * It can be directly inserted into its
271
             * B+tree of known futexes.
272
             */
273
            mutex_lock(&TASK->futexes_lock);
274
            btree_insert(&TASK->futexes, paddr, futex, NULL);
275
            mutex_unlock(&TASK->futexes_lock);
276
 
1153 jermar 277
            rwlock_write_unlock(&futex_ht_lock);
278
        }
1109 jermar 279
    }
280
 
1153 jermar 281
    return futex;
1109 jermar 282
}
283
 
284
/** Compute hash index into futex hash table.
285
 *
2087 jermar 286
 * @param key Address where the key (i.e. physical address of futex counter) is
287
 *     stored.
1109 jermar 288
 *
289
 * @return Index into futex hash table.
290
 */
4490 decky 291
size_t futex_ht_hash(unative_t *key)
1109 jermar 292
{
4490 decky 293
    return (*key & (FUTEX_HT_SIZE - 1));
1109 jermar 294
}
295
 
296
/** Compare futex hash table item with a key.
297
 *
2087 jermar 298
 * @param key Address where the key (i.e. physical address of futex counter) is
299
 *     stored.
1109 jermar 300
 *
1248 jermar 301
 * @return True if the item matches the key. False otherwise.
1109 jermar 302
 */
4490 decky 303
bool futex_ht_compare(unative_t *key, size_t keys, link_t *item)
1109 jermar 304
{
305
    futex_t *futex;
306
 
307
    ASSERT(keys == 1);
308
 
309
    futex = hash_table_get_instance(item, futex_t, ht_link);
310
    return *key == futex->paddr;
311
}
312
 
313
/** Callback for removal items from futex hash table.
314
 *
315
 * @param item Item removed from the hash table.
316
 */
317
void futex_ht_remove_callback(link_t *item)
318
{
319
    futex_t *futex;
320
 
321
    futex = hash_table_get_instance(item, futex_t, ht_link);
322
    free(futex);
323
}
1583 jermar 324
 
325
/** Remove references from futexes known to the current task. */
326
void futex_cleanup(void)
327
{
1586 jermar 328
    link_t *cur;
329
 
330
    rwlock_write_lock(&futex_ht_lock);
331
    mutex_lock(&TASK->futexes_lock);
332
 
2087 jermar 333
    for (cur = TASK->futexes.leaf_head.next;
334
        cur != &TASK->futexes.leaf_head; cur = cur->next) {
1586 jermar 335
        btree_node_t *node;
2745 decky 336
        unsigned int i;
1586 jermar 337
 
338
        node = list_get_instance(cur, btree_node_t, leaf_link);
339
        for (i = 0; i < node->keys; i++) {
340
            futex_t *ftx;
1780 jermar 341
            uintptr_t paddr = node->key[i];
1586 jermar 342
 
343
            ftx = (futex_t *) node->value[i];
344
            if (--ftx->refcount == 0)
345
                hash_table_remove(&futex_ht, &paddr, 1);
346
        }
347
    }
348
 
349
    mutex_unlock(&TASK->futexes_lock);
350
    rwlock_write_unlock(&futex_ht_lock);
1583 jermar 351
}
1702 cejka 352
 
1757 jermar 353
/** @}
1702 cejka 354
 */