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1109 | jermar | 1 | /* |
2 | * Copyright (C) 2006 Jakub Jermar |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * |
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9 | * - Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * - Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * - The name of the author may not be used to endorse or promote products |
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15 | * derived from this software without specific prior written permission. |
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16 | * |
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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27 | */ |
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28 | |||
1757 | jermar | 29 | /** @addtogroup sync |
1702 | cejka | 30 | * @{ |
31 | */ |
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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> |
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39 | #include <synch/rwlock.h> |
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1117 | jermar | 40 | #include <synch/spinlock.h> |
1109 | jermar | 41 | #include <synch/synch.h> |
42 | #include <mm/frame.h> |
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43 | #include <mm/page.h> |
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44 | #include <mm/slab.h> |
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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> |
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49 | #include <adt/hash_table.h> |
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50 | #include <adt/list.h> |
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51 | #include <arch.h> |
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52 | #include <align.h> |
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53 | #include <panic.h> |
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54 | #include <errno.h> |
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55 | #include <print.h> |
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56 | |||
57 | #define FUTEX_HT_SIZE 1024 /* keep it a power of 2 */ |
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58 | |||
59 | static void futex_initialize(futex_t *futex); |
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60 | |||
1153 | jermar | 61 | static futex_t *futex_find(__address paddr); |
1109 | jermar | 62 | static index_t futex_ht_hash(__native *key); |
63 | static bool futex_ht_compare(__native *key, count_t keys, link_t *item); |
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64 | static void futex_ht_remove_callback(link_t *item); |
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65 | |||
1460 | jermar | 66 | /** |
67 | * Read-write lock protecting global futex hash table. |
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68 | * It is also used to serialize access to all futex_t structures. |
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69 | * Must be acquired before the task futex B+tree lock. |
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70 | */ |
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1109 | jermar | 71 | static rwlock_t futex_ht_lock; |
72 | |||
73 | /** Futex hash table. */ |
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74 | static hash_table_t futex_ht; |
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75 | |||
76 | /** Futex hash table operations. */ |
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77 | static hash_table_operations_t futex_ht_ops = { |
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78 | .hash = futex_ht_hash, |
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79 | .compare = futex_ht_compare, |
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80 | .remove_callback = futex_ht_remove_callback |
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81 | }; |
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82 | |||
83 | /** Initialize futex subsystem. */ |
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84 | void futex_init(void) |
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85 | { |
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86 | rwlock_initialize(&futex_ht_lock); |
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87 | hash_table_create(&futex_ht, FUTEX_HT_SIZE, 1, &futex_ht_ops); |
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88 | } |
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89 | |||
90 | /** Initialize kernel futex structure. |
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91 | * |
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92 | * @param futex Kernel futex structure. |
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93 | */ |
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94 | void futex_initialize(futex_t *futex) |
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95 | { |
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96 | waitq_initialize(&futex->wq); |
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97 | link_initialize(&futex->ht_link); |
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98 | futex->paddr = 0; |
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1460 | jermar | 99 | futex->refcount = 1; |
1109 | jermar | 100 | } |
101 | |||
102 | /** Sleep in futex wait queue. |
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103 | * |
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104 | * @param uaddr Userspace address of the futex counter. |
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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 | */ |
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1502 | jermar | 111 | __native sys_futex_sleep_timeout(__address uaddr, __u32 usec, int flags) |
1109 | jermar | 112 | { |
113 | futex_t *futex; |
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114 | __address paddr; |
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115 | pte_t *t; |
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1117 | jermar | 116 | ipl_t ipl; |
1109 | jermar | 117 | |
1117 | jermar | 118 | ipl = interrupts_disable(); |
119 | |||
1109 | jermar | 120 | /* |
121 | * Find physical address of futex counter. |
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122 | */ |
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123 | page_table_lock(AS, true); |
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124 | t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
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125 | if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
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126 | page_table_unlock(AS, true); |
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1117 | jermar | 127 | interrupts_restore(ipl); |
1109 | jermar | 128 | return (__native) ENOENT; |
129 | } |
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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. |
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141 | * |
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142 | * @param uaddr Userspace address of the futex counter. |
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143 | * |
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1414 | jermar | 144 | * @return ENOENT if there is no physical mapping for uaddr. |
1109 | jermar | 145 | */ |
146 | __native sys_futex_wakeup(__address uaddr) |
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147 | { |
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1153 | jermar | 148 | futex_t *futex; |
1109 | jermar | 149 | __address paddr; |
150 | pte_t *t; |
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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. |
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157 | */ |
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158 | page_table_lock(AS, true); |
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159 | t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
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160 | if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
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161 | page_table_unlock(AS, true); |
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1117 | jermar | 162 | interrupts_restore(ipl); |
1109 | jermar | 163 | return (__native) ENOENT; |
164 | } |
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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); |
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173 | |||
174 | return 0; |
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175 | } |
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176 | |||
177 | /** Find kernel address of the futex structure corresponding to paddr. |
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178 | * |
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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. |
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182 | * |
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183 | * @return Address of the kernel futex structure. |
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184 | */ |
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185 | futex_t *futex_find(__address paddr) |
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186 | { |
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187 | link_t *item; |
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188 | futex_t *futex; |
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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. |
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1109 | jermar | 194 | */ |
195 | rwlock_read_lock(&futex_ht_lock); |
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196 | item = hash_table_find(&futex_ht, &paddr); |
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197 | if (item) { |
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198 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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1460 | jermar | 199 | |
200 | /* |
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201 | * See if the current task knows this futex. |
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202 | */ |
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203 | mutex_lock(&TASK->futexes_lock); |
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204 | if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
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205 | /* |
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206 | * The futex is new to the current task. |
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207 | * However, we only have read access. |
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208 | * Gain write access and try again. |
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209 | */ |
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210 | mutex_unlock(&TASK->futexes_lock); |
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211 | goto gain_write_access; |
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212 | } |
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213 | mutex_unlock(&TASK->futexes_lock); |
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214 | |||
1153 | jermar | 215 | rwlock_read_unlock(&futex_ht_lock); |
216 | } else { |
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1460 | jermar | 217 | gain_write_access: |
1153 | jermar | 218 | /* |
219 | * Upgrade to writer is not currently supported, |
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1414 | jermar | 220 | * therefore, it is necessary to release the read lock |
1153 | jermar | 221 | * and reacquire it as a writer. |
222 | */ |
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223 | rwlock_read_unlock(&futex_ht_lock); |
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224 | |||
225 | rwlock_write_lock(&futex_ht_lock); |
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226 | /* |
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227 | * Avoid possible race condition by searching |
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228 | * the hash table once again with write access. |
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229 | */ |
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230 | item = hash_table_find(&futex_ht, &paddr); |
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231 | if (item) { |
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232 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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1460 | jermar | 233 | |
234 | /* |
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235 | * See if this futex is known to the current task. |
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236 | */ |
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237 | mutex_lock(&TASK->futexes_lock); |
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238 | if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
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239 | /* |
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240 | * The futex is new to the current task. |
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241 | * Upgrade its reference count and put it to the |
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242 | * current task's B+tree of known futexes. |
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243 | */ |
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244 | futex->refcount++; |
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245 | btree_insert(&TASK->futexes, paddr, futex, leaf); |
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246 | } |
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247 | mutex_unlock(&TASK->futexes_lock); |
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248 | |||
1153 | jermar | 249 | rwlock_write_unlock(&futex_ht_lock); |
250 | } else { |
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251 | futex = (futex_t *) malloc(sizeof(futex_t), 0); |
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252 | futex_initialize(futex); |
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253 | futex->paddr = paddr; |
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254 | hash_table_insert(&futex_ht, &paddr, &futex->ht_link); |
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1460 | jermar | 255 | |
256 | /* |
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257 | * This is the first task referencing the futex. |
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258 | * It can be directly inserted into its |
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259 | * B+tree of known futexes. |
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260 | */ |
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261 | mutex_lock(&TASK->futexes_lock); |
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262 | btree_insert(&TASK->futexes, paddr, futex, NULL); |
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263 | mutex_unlock(&TASK->futexes_lock); |
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264 | |||
1153 | jermar | 265 | rwlock_write_unlock(&futex_ht_lock); |
266 | } |
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1109 | jermar | 267 | } |
268 | |||
1153 | jermar | 269 | return futex; |
1109 | jermar | 270 | } |
271 | |||
272 | /** Compute hash index into futex hash table. |
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273 | * |
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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. |
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277 | */ |
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278 | index_t futex_ht_hash(__native *key) |
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279 | { |
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280 | return *key & (FUTEX_HT_SIZE-1); |
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281 | } |
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282 | |||
283 | /** Compare futex hash table item with a key. |
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284 | * |
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285 | * @param key Address where the key (i.e. physical address of futex counter) is stored. |
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286 | * |
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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) |
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290 | { |
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291 | futex_t *futex; |
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292 | |||
293 | ASSERT(keys == 1); |
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294 | |||
295 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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296 | return *key == futex->paddr; |
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297 | } |
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298 | |||
299 | /** Callback for removal items from futex hash table. |
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300 | * |
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301 | * @param item Item removed from the hash table. |
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302 | */ |
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303 | void futex_ht_remove_callback(link_t *item) |
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304 | { |
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305 | futex_t *futex; |
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306 | |||
307 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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308 | free(futex); |
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309 | } |
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1583 | jermar | 310 | |
311 | /** Remove references from futexes known to the current task. */ |
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312 | void futex_cleanup(void) |
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313 | { |
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1586 | jermar | 314 | link_t *cur; |
315 | |||
316 | rwlock_write_lock(&futex_ht_lock); |
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317 | mutex_lock(&TASK->futexes_lock); |
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318 | |||
319 | for (cur = TASK->futexes.leaf_head.next; cur != &TASK->futexes.leaf_head; cur = cur->next) { |
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320 | btree_node_t *node; |
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321 | int i; |
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322 | |||
323 | node = list_get_instance(cur, btree_node_t, leaf_link); |
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324 | for (i = 0; i < node->keys; i++) { |
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325 | futex_t *ftx; |
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326 | __address paddr = node->key[i]; |
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327 | |||
328 | ftx = (futex_t *) node->value[i]; |
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329 | if (--ftx->refcount == 0) |
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330 | hash_table_remove(&futex_ht, &paddr, 1); |
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331 | } |
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332 | } |
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333 | |||
334 | mutex_unlock(&TASK->futexes_lock); |
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335 | rwlock_write_unlock(&futex_ht_lock); |
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1583 | jermar | 336 | } |
1702 | cejka | 337 | |
1757 | jermar | 338 | /** @} |
1702 | cejka | 339 | */ |