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1109 | jermar | 1 | /* |
2071 | jermar | 2 | * Copyright (c) 2006 Jakub Jermar |
1109 | jermar | 3 | * All rights reserved. |
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 | |||
1780 | jermar | 61 | static futex_t *futex_find(uintptr_t paddr); |
62 | static index_t futex_ht_hash(unative_t *key); |
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63 | static bool futex_ht_compare(unative_t *key, count_t keys, link_t *item); |
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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. |
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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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2087 | jermar | 105 | * @param usec If non-zero, number of microseconds this thread is willing to |
106 | * sleep. |
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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. |
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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; |
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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. |
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123 | */ |
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124 | page_table_lock(AS, true); |
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125 | t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
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126 | if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
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127 | page_table_unlock(AS, true); |
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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); |
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1109 | jermar | 140 | } |
141 | |||
142 | /** Wakeup one thread waiting in futex wait queue. |
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143 | * |
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144 | * @param uaddr Userspace address of the futex counter. |
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145 | * |
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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. |
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159 | */ |
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160 | page_table_lock(AS, true); |
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161 | t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE)); |
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162 | if (!t || !PTE_VALID(t) || !PTE_PRESENT(t)) { |
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163 | page_table_unlock(AS, true); |
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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); |
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175 | |||
176 | return 0; |
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177 | } |
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178 | |||
179 | /** Find kernel address of the futex structure corresponding to paddr. |
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180 | * |
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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. |
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184 | * |
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185 | * @return Address of the kernel futex structure. |
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186 | */ |
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1780 | jermar | 187 | futex_t *futex_find(uintptr_t paddr) |
1153 | jermar | 188 | { |
189 | link_t *item; |
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190 | futex_t *futex; |
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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. |
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1109 | jermar | 196 | */ |
197 | rwlock_read_lock(&futex_ht_lock); |
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198 | item = hash_table_find(&futex_ht, &paddr); |
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199 | if (item) { |
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200 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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1460 | jermar | 201 | |
202 | /* |
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203 | * See if the current task knows this futex. |
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204 | */ |
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205 | mutex_lock(&TASK->futexes_lock); |
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206 | if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
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207 | /* |
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208 | * The futex is new to the current task. |
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209 | * However, we only have read access. |
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210 | * Gain write access and try again. |
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211 | */ |
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212 | mutex_unlock(&TASK->futexes_lock); |
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213 | goto gain_write_access; |
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214 | } |
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215 | mutex_unlock(&TASK->futexes_lock); |
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216 | |||
1153 | jermar | 217 | rwlock_read_unlock(&futex_ht_lock); |
218 | } else { |
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1460 | jermar | 219 | gain_write_access: |
1153 | jermar | 220 | /* |
221 | * Upgrade to writer is not currently supported, |
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1414 | jermar | 222 | * therefore, it is necessary to release the read lock |
1153 | jermar | 223 | * and reacquire it as a writer. |
224 | */ |
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225 | rwlock_read_unlock(&futex_ht_lock); |
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226 | |||
227 | rwlock_write_lock(&futex_ht_lock); |
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228 | /* |
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229 | * Avoid possible race condition by searching |
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230 | * the hash table once again with write access. |
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231 | */ |
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232 | item = hash_table_find(&futex_ht, &paddr); |
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233 | if (item) { |
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234 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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1460 | jermar | 235 | |
236 | /* |
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237 | * See if this futex is known to the current task. |
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238 | */ |
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239 | mutex_lock(&TASK->futexes_lock); |
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240 | if (!btree_search(&TASK->futexes, paddr, &leaf)) { |
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241 | /* |
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242 | * The futex is new to the current task. |
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243 | * Upgrade its reference count and put it to the |
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244 | * current task's B+tree of known futexes. |
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245 | */ |
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246 | futex->refcount++; |
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2087 | jermar | 247 | btree_insert(&TASK->futexes, paddr, futex, |
248 | leaf); |
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1460 | jermar | 249 | } |
250 | mutex_unlock(&TASK->futexes_lock); |
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251 | |||
1153 | jermar | 252 | rwlock_write_unlock(&futex_ht_lock); |
253 | } else { |
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254 | futex = (futex_t *) malloc(sizeof(futex_t), 0); |
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255 | futex_initialize(futex); |
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256 | futex->paddr = paddr; |
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257 | hash_table_insert(&futex_ht, &paddr, &futex->ht_link); |
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1460 | jermar | 258 | |
259 | /* |
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260 | * This is the first task referencing the futex. |
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261 | * It can be directly inserted into its |
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262 | * B+tree of known futexes. |
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263 | */ |
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264 | mutex_lock(&TASK->futexes_lock); |
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265 | btree_insert(&TASK->futexes, paddr, futex, NULL); |
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266 | mutex_unlock(&TASK->futexes_lock); |
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267 | |||
1153 | jermar | 268 | rwlock_write_unlock(&futex_ht_lock); |
269 | } |
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1109 | jermar | 270 | } |
271 | |||
1153 | jermar | 272 | return futex; |
1109 | jermar | 273 | } |
274 | |||
275 | /** Compute hash index into futex hash table. |
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276 | * |
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2087 | jermar | 277 | * @param key Address where the key (i.e. physical address of futex counter) is |
278 | * stored. |
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1109 | jermar | 279 | * |
280 | * @return Index into futex hash table. |
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281 | */ |
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1780 | jermar | 282 | index_t futex_ht_hash(unative_t *key) |
1109 | jermar | 283 | { |
284 | return *key & (FUTEX_HT_SIZE-1); |
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285 | } |
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286 | |||
287 | /** Compare futex hash table item with a key. |
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288 | * |
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2087 | jermar | 289 | * @param key Address where the key (i.e. physical address of futex counter) is |
290 | * stored. |
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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; |
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297 | |||
298 | ASSERT(keys == 1); |
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299 | |||
300 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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301 | return *key == futex->paddr; |
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302 | } |
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303 | |||
304 | /** Callback for removal items from futex hash table. |
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305 | * |
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306 | * @param item Item removed from the hash table. |
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307 | */ |
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308 | void futex_ht_remove_callback(link_t *item) |
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309 | { |
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310 | futex_t *futex; |
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311 | |||
312 | futex = hash_table_get_instance(item, futex_t, ht_link); |
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313 | free(futex); |
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314 | } |
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1583 | jermar | 315 | |
316 | /** Remove references from futexes known to the current task. */ |
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317 | void futex_cleanup(void) |
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318 | { |
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1586 | jermar | 319 | link_t *cur; |
320 | |||
321 | rwlock_write_lock(&futex_ht_lock); |
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322 | mutex_lock(&TASK->futexes_lock); |
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323 | |||
2087 | jermar | 324 | for (cur = TASK->futexes.leaf_head.next; |
325 | cur != &TASK->futexes.leaf_head; cur = cur->next) { |
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1586 | jermar | 326 | btree_node_t *node; |
2745 | decky | 327 | unsigned int i; |
1586 | jermar | 328 | |
329 | node = list_get_instance(cur, btree_node_t, leaf_link); |
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330 | for (i = 0; i < node->keys; i++) { |
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331 | futex_t *ftx; |
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1780 | jermar | 332 | uintptr_t paddr = node->key[i]; |
1586 | jermar | 333 | |
334 | ftx = (futex_t *) node->value[i]; |
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335 | if (--ftx->refcount == 0) |
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336 | hash_table_remove(&futex_ht, &paddr, 1); |
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337 | } |
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338 | } |
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339 | |||
340 | mutex_unlock(&TASK->futexes_lock); |
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341 | rwlock_write_unlock(&futex_ht_lock); |
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1583 | jermar | 342 | } |
1702 | cejka | 343 | |
1757 | jermar | 344 | /** @} |
1702 | cejka | 345 | */ |