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1109 jermar 1
/*
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 * Copyright (C) 2006 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * 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
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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1757 jermar 29
/** @addtogroup sync
1702 cejka 30
 * @{
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 */
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1109 jermar 33
/**
1702 cejka 34
 * @file
1264 jermar 35
 * @brief   Kernel backend for futexes.
1109 jermar 36
 */
37
 
38
#include <synch/futex.h>
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#include <synch/rwlock.h>
1117 jermar 40
#include <synch/spinlock.h>
1109 jermar 41
#include <synch/synch.h>
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#include <mm/frame.h>
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#include <mm/page.h>
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#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>
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#include <genarch/mm/page_ht.h>
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#include <adt/hash_table.h>
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#include <adt/list.h>
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#include <arch.h>
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#include <align.h>
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#include <panic.h>
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#include <errno.h>
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#include <print.h>
56
 
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#define FUTEX_HT_SIZE   1024    /* keep it a power of 2 */
58
 
59
static void futex_initialize(futex_t *futex);
60
 
1153 jermar 61
static futex_t *futex_find(__address paddr);
1109 jermar 62
static index_t futex_ht_hash(__native *key);
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static bool futex_ht_compare(__native *key, count_t keys, link_t *item);
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static void futex_ht_remove_callback(link_t *item);
65
 
1460 jermar 66
/**
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 * Read-write lock protecting global futex hash table.
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 * It is also used to serialize access to all futex_t structures.
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 * Must be acquired before the task futex B+tree lock.
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 */
1109 jermar 71
static rwlock_t futex_ht_lock;
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73
/** Futex hash table. */
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static hash_table_t futex_ht;
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76
/** Futex hash table operations. */
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static hash_table_operations_t futex_ht_ops = {
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    .hash = futex_ht_hash,
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    .compare = futex_ht_compare,
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    .remove_callback = futex_ht_remove_callback
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};
82
 
83
/** Initialize futex subsystem. */
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void futex_init(void)
85
{
86
    rwlock_initialize(&futex_ht_lock);
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    hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops);
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}
89
 
90
/** Initialize kernel futex structure.
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 *
92
 * @param futex Kernel futex structure.
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 */
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void futex_initialize(futex_t *futex)
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{
96
    waitq_initialize(&futex->wq);
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    link_initialize(&futex->ht_link);
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    futex->paddr = 0;
1460 jermar 99
    futex->refcount = 1;
1109 jermar 100
}
101
 
102
/** Sleep in futex wait queue.
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 *
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 * @param uaddr Userspace address of the futex counter.
1117 jermar 105
 * @param usec If non-zero, number of microseconds this thread is willing to sleep.
1502 jermar 106
 * @param flags Select mode of operation.
1109 jermar 107
 *
1117 jermar 108
 * @return One of ESYNCH_TIMEOUT, ESYNCH_OK_ATOMIC and ESYNCH_OK_BLOCKED. See synch.h.
1109 jermar 109
 *     If there is no physical mapping for uaddr ENOENT is returned.
110
 */
1502 jermar 111
__native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int flags)
1109 jermar 112
{
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    futex_t *futex;
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    __address paddr;
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    pte_t *t;
1117 jermar 116
    ipl_t ipl;
1109 jermar 117
 
1117 jermar 118
    ipl = interrupts_disable();
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1109 jermar 120
    /*
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     * Find physical address of futex counter.
122
     */
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    page_table_lock(AS, true);
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    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
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    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
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        page_table_unlock(AS, true);
1117 jermar 127
        interrupts_restore(ipl);
1109 jermar 128
        return (__native) ENOENT;
129
    }
1414 jermar 130
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 131
    page_table_unlock(AS, true);
132
 
1117 jermar 133
    interrupts_restore(ipl);   
134
 
1153 jermar 135
    futex = futex_find(paddr);
1109 jermar 136
 
1502 jermar 137
    return (__native) waitq_sleep_timeout(&futex->wq, usec, flags | SYNCH_FLAGS_INTERRUPTIBLE);
1109 jermar 138
}
139
 
140
/** Wakeup one thread waiting in futex wait queue.
141
 *
142
 * @param uaddr Userspace address of the futex counter.
143
 *
1414 jermar 144
 * @return ENOENT if there is no physical mapping for uaddr.
1109 jermar 145
 */
146
__native sys_futex_wakeup(__address uaddr)
147
{
1153 jermar 148
    futex_t *futex;
1109 jermar 149
    __address paddr;
150
    pte_t *t;
1117 jermar 151
    ipl_t ipl;
1109 jermar 152
 
1117 jermar 153
    ipl = interrupts_disable();
154
 
1109 jermar 155
    /*
156
     * Find physical address of futex counter.
157
     */
158
    page_table_lock(AS, true);
159
    t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE));
160
    if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) {
161
        page_table_unlock(AS, true);
1117 jermar 162
        interrupts_restore(ipl);
1109 jermar 163
        return (__native) ENOENT;
164
    }
1414 jermar 165
    paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
1109 jermar 166
    page_table_unlock(AS, true);
167
 
1117 jermar 168
    interrupts_restore(ipl);
169
 
1153 jermar 170
    futex = futex_find(paddr);
171
 
172
    waitq_wakeup(&futex->wq, WAKEUP_FIRST);
173
 
174
    return 0;
175
}
176
 
177
/** Find kernel address of the futex structure corresponding to paddr.
178
 *
1460 jermar 179
 * If the structure does not exist already, a new one is created.
1153 jermar 180
 *
181
 * @param paddr Physical address of the userspace futex counter.
182
 *
183
 * @return Address of the kernel futex structure.
184
 */
185
futex_t *futex_find(__address paddr)
186
{
187
    link_t *item;
188
    futex_t *futex;
1460 jermar 189
    btree_node_t *leaf;
1153 jermar 190
 
1109 jermar 191
    /*
1153 jermar 192
     * Find the respective futex structure
193
     * or allocate new one if it does not exist already.
1109 jermar 194
     */
195
    rwlock_read_lock(&futex_ht_lock);
196
    item = hash_table_find(&futex_ht, &paddr);
197
    if (item) {
198
        futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 199
 
200
        /*
201
         * See if the current task knows this futex.
202
         */
203
        mutex_lock(&TASK->futexes_lock);
204
        if (!btree_search(&TASK->futexes, paddr, &leaf)) {
205
            /*
206
             * The futex is new to the current task.
207
             * However, we only have read access.
208
             * Gain write access and try again.
209
             */
210
            mutex_unlock(&TASK->futexes_lock);
211
            goto gain_write_access;
212
        }
213
        mutex_unlock(&TASK->futexes_lock);
214
 
1153 jermar 215
        rwlock_read_unlock(&futex_ht_lock);
216
    } else {
1460 jermar 217
gain_write_access:
1153 jermar 218
        /*
219
         * Upgrade to writer is not currently supported,
1414 jermar 220
         * therefore, it is necessary to release the read lock
1153 jermar 221
         * and reacquire it as a writer.
222
         */
223
        rwlock_read_unlock(&futex_ht_lock);
224
 
225
        rwlock_write_lock(&futex_ht_lock);
226
        /*
227
         * Avoid possible race condition by searching
228
         * the hash table once again with write access.
229
         */
230
        item = hash_table_find(&futex_ht, &paddr);
231
        if (item) {
232
            futex = hash_table_get_instance(item, futex_t, ht_link);
1460 jermar 233
 
234
            /*
235
             * See if this futex is known to the current task.
236
             */
237
            mutex_lock(&TASK->futexes_lock);
238
            if (!btree_search(&TASK->futexes, paddr, &leaf)) {
239
                /*
240
                 * The futex is new to the current task.
241
                 * Upgrade its reference count and put it to the
242
                 * current task's B+tree of known futexes.
243
                 */
244
                futex->refcount++;
245
                btree_insert(&TASK->futexes, paddr, futex, leaf);
246
            }
247
            mutex_unlock(&TASK->futexes_lock);
248
 
1153 jermar 249
            rwlock_write_unlock(&futex_ht_lock);
250
        } else {
251
            futex = (futex_t *) malloc(sizeof(futex_t), 0);
252
            futex_initialize(futex);
253
            futex->paddr = paddr;
254
            hash_table_insert(&futex_ht, &paddr, &futex->ht_link);
1460 jermar 255
 
256
            /*
257
             * This is the first task referencing the futex.
258
             * It can be directly inserted into its
259
             * B+tree of known futexes.
260
             */
261
            mutex_lock(&TASK->futexes_lock);
262
            btree_insert(&TASK->futexes, paddr, futex, NULL);
263
            mutex_unlock(&TASK->futexes_lock);
264
 
1153 jermar 265
            rwlock_write_unlock(&futex_ht_lock);
266
        }
1109 jermar 267
    }
268
 
1153 jermar 269
    return futex;
1109 jermar 270
}
271
 
272
/** Compute hash index into futex hash table.
273
 *
1248 jermar 274
 * @param key Address where the key (i.e. physical address of futex counter) is stored.
1109 jermar 275
 *
276
 * @return Index into futex hash table.
277
 */
278
index_t futex_ht_hash(__native *key)
279
{
280
    return *key & (FUTEX_HT_SIZE-1);
281
}
282
 
283
/** Compare futex hash table item with a key.
284
 *
285
 * @param key Address where the key (i.e. physical address of futex counter) is stored.
286
 *
1248 jermar 287
 * @return True if the item matches the key. False otherwise.
1109 jermar 288
 */
289
bool futex_ht_compare(__native *key, count_t keys, link_t *item)
290
{
291
    futex_t *futex;
292
 
293
    ASSERT(keys == 1);
294
 
295
    futex = hash_table_get_instance(item, futex_t, ht_link);
296
    return *key == futex->paddr;
297
}
298
 
299
/** Callback for removal items from futex hash table.
300
 *
301
 * @param item Item removed from the hash table.
302
 */
303
void futex_ht_remove_callback(link_t *item)
304
{
305
    futex_t *futex;
306
 
307
    futex = hash_table_get_instance(item, futex_t, ht_link);
308
    free(futex);
309
}
1583 jermar 310
 
311
/** Remove references from futexes known to the current task. */
312
void futex_cleanup(void)
313
{
1586 jermar 314
    link_t *cur;
315
 
316
    rwlock_write_lock(&futex_ht_lock);
317
    mutex_lock(&TASK->futexes_lock);
318
 
319
    for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) {
320
        btree_node_t *node;
321
        int i;
322
 
323
        node = list_get_instance(cur, btree_node_t, leaf_link);
324
        for (i = 0; i < node->keys; i++) {
325
            futex_t *ftx;
326
            __address paddr = node->key[i];
327
 
328
            ftx = (futex_t *) node->value[i];
329
            if (--ftx->refcount == 0)
330
                hash_table_remove(&futex_ht, &paddr, 1);
331
        }
332
    }
333
 
334
    mutex_unlock(&TASK->futexes_lock);
335
    rwlock_write_unlock(&futex_ht_lock);
1583 jermar 336
}
1702 cejka 337
 
1757 jermar 338
/** @}
1702 cejka 339
 */