root / prex-0.9.0 / sys / sync / cond.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*-
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2 | * Copyright (c) 2005-2007, Kohsuke Ohtani
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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 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | * 3. Neither the name of the author nor the names of any co-contributors
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14 | * may be used to endorse or promote products derived from this software
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15 | * without specific prior written permission.
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16 | *
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 | * SUCH DAMAGE.
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28 | */
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29 | |||
30 | /*
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31 | * cond.c - condition variable object
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32 | */
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33 | |||
34 | #include <kernel.h> |
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35 | #include <sched.h> |
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36 | #include <event.h> |
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37 | #include <kmem.h> |
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38 | #include <task.h> |
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39 | #include <sync.h> |
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40 | |||
41 | /* forward declarations */
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42 | static int cond_valid(cond_t); |
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43 | static int cond_copyin(cond_t *, cond_t *); |
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44 | |||
45 | /*
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46 | * Create and initialize a condition variable (CV).
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47 | *
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48 | * If an initialized condition variable is reinitialized,
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49 | * undefined behavior results.
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50 | */
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51 | int
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52 | cond_init(cond_t *cp) |
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53 | { |
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54 | task_t self = curtask; |
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55 | cond_t c; |
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56 | |||
57 | if (self->nsyncs >= MAXSYNCS)
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58 | return EAGAIN;
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59 | |||
60 | if ((c = kmem_alloc(sizeof(struct cond))) == NULL) |
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61 | return ENOMEM;
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62 | |||
63 | event_init(&c->event, "condvar");
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64 | c->owner = self; |
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65 | |||
66 | if (copyout(&c, cp, sizeof(c))) { |
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67 | kmem_free(c); |
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68 | return EFAULT;
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69 | } |
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70 | sched_lock(); |
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71 | list_insert(&self->conds, &c->task_link); |
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72 | self->nsyncs++; |
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73 | sched_unlock(); |
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74 | return 0; |
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75 | } |
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76 | |||
77 | static void |
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78 | cond_deallocate(cond_t c) |
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79 | { |
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80 | |||
81 | c->owner->nsyncs--; |
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82 | list_remove(&c->task_link); |
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83 | kmem_free(c); |
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84 | } |
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85 | |||
86 | /*
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87 | * Tear down a condition variable.
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88 | *
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89 | * If there are any blocked thread waiting for the specified
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90 | * CV, it returns EBUSY.
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91 | */
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92 | int
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93 | cond_destroy(cond_t *cp) |
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94 | { |
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95 | cond_t c; |
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96 | |||
97 | sched_lock(); |
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98 | if (cond_copyin(cp, &c)) {
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99 | sched_unlock(); |
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100 | return EINVAL;
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101 | } |
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102 | if (event_waiting(&c->event)) {
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103 | sched_unlock(); |
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104 | return EBUSY;
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105 | } |
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106 | cond_deallocate(c); |
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107 | sched_unlock(); |
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108 | return 0; |
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109 | } |
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110 | |||
111 | /*
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112 | * Clean up for task termination.
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113 | */
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114 | void
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115 | cond_cleanup(task_t task) |
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116 | { |
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117 | cond_t c; |
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118 | |||
119 | while (!list_empty(&task->conds)) {
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120 | c = list_entry(list_first(&task->conds), |
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121 | struct cond, task_link);
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122 | cond_deallocate(c); |
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123 | } |
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124 | } |
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125 | |||
126 | /*
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127 | * Wait on a condition.
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128 | *
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129 | * If the thread receives any exception while waiting CV, this
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130 | * routine returns immediately with EINTR in order to invoke
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131 | * exception handler. However, an application assumes this call
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132 | * does NOT return with an error. So, the stub routine in a
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133 | * system call library must call cond_wait() again if it gets
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134 | * EINTR as error.
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135 | */
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136 | int
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137 | cond_wait(cond_t *cp, mutex_t *mp) |
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138 | { |
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139 | cond_t c; |
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140 | int error, rc;
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141 | |||
142 | if (copyin(cp, &c, sizeof(cp))) |
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143 | return EINVAL;
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144 | |||
145 | sched_lock(); |
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146 | if (c == COND_INITIALIZER) {
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147 | if ((error = cond_init(cp)) != 0) { |
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148 | sched_unlock(); |
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149 | return error;
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150 | } |
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151 | copyin(cp, &c, sizeof(cp));
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152 | } else {
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153 | if (!cond_valid(c)) {
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154 | sched_unlock(); |
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155 | return EINVAL;
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156 | } |
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157 | } |
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158 | /* unlock mutex */
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159 | if ((error = mutex_unlock(mp)) != 0) { |
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160 | sched_unlock(); |
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161 | return error;
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162 | } |
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163 | |||
164 | /* and block */
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165 | rc = sched_sleep(&c->event); |
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166 | if (rc == SLP_INTR)
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167 | error = EINTR; |
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168 | sched_unlock(); |
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169 | |||
170 | /* grab mutex before returning */
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171 | if (error == 0) |
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172 | error = mutex_lock(mp); |
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173 | |||
174 | return error;
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175 | } |
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176 | |||
177 | /*
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178 | * Unblock one thread that is blocked on the specified CV.
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179 | * The thread which has highest priority will be unblocked.
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180 | */
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181 | int
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182 | cond_signal(cond_t *cp) |
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183 | { |
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184 | cond_t c; |
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185 | |||
186 | sched_lock(); |
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187 | if (cond_copyin(cp, &c)) {
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188 | sched_unlock(); |
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189 | return EINVAL;
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190 | } |
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191 | sched_wakeone(&c->event); |
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192 | sched_unlock(); |
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193 | return 0; |
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194 | } |
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195 | |||
196 | /*
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197 | * Unblock all threads that are blocked on the specified CV.
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198 | */
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199 | int
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200 | cond_broadcast(cond_t *cp) |
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201 | { |
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202 | cond_t c; |
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203 | |||
204 | sched_lock(); |
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205 | if (cond_copyin(cp, &c)) {
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206 | sched_unlock(); |
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207 | return EINVAL;
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208 | } |
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209 | sched_wakeup(&c->event); |
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210 | sched_unlock(); |
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211 | return 0; |
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212 | } |
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213 | |||
214 | /*
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215 | * Check if the specified cv is valid.
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216 | */
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217 | static int |
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218 | cond_valid(cond_t c) |
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219 | { |
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220 | cond_t tmp; |
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221 | list_t head, n; |
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222 | |||
223 | head = &curtask->conds; |
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224 | for (n = list_first(head); n != head; n = list_next(n)) {
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225 | tmp = list_entry(n, struct cond, task_link);
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226 | if (tmp == c)
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227 | return 1; |
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228 | } |
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229 | return 0; |
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230 | } |
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231 | |||
232 | /*
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233 | * cond_copyin - copy a condition variable from user space.
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234 | * It also checks if the passed CV is valid.
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235 | */
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236 | static int |
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237 | cond_copyin(cond_t *ucp, cond_t *kcp) |
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238 | { |
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239 | cond_t c; |
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240 | |||
241 | if (copyin(ucp, &c, sizeof(ucp)) || !cond_valid(c)) |
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242 | return EINVAL;
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243 | *kcp = c; |
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244 | return 0; |
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245 | } |