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5060 | serge | 1 | /* |
2 | * Copyright (C) 2014 Red Hat |
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3 | * Author: Rob Clark |
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4 | * |
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5 | * Permission is hereby granted, free of charge, to any person obtaining a |
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6 | * copy of this software and associated documentation files (the "Software"), |
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7 | * to deal in the Software without restriction, including without limitation |
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8 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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9 | * and/or sell copies of the Software, and to permit persons to whom the |
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10 | * Software is furnished to do so, subject to the following conditions: |
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11 | * |
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12 | * The above copyright notice and this permission notice shall be included in |
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13 | * all copies or substantial portions of the Software. |
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14 | * |
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15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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18 | * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR |
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19 | * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, |
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20 | * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR |
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21 | * OTHER DEALINGS IN THE SOFTWARE. |
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22 | */ |
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23 | |||
24 | #include |
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25 | #include |
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26 | #include |
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27 | |||
28 | /** |
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29 | * DOC: kms locking |
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30 | * |
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31 | * As KMS moves toward more fine grained locking, and atomic ioctl where |
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32 | * userspace can indirectly control locking order, it becomes necessary |
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33 | * to use ww_mutex and acquire-contexts to avoid deadlocks. But because |
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34 | * the locking is more distributed around the driver code, we want a bit |
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35 | * of extra utility/tracking out of our acquire-ctx. This is provided |
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36 | * by drm_modeset_lock / drm_modeset_acquire_ctx. |
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37 | * |
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5271 | serge | 38 | * For basic principles of ww_mutex, see: Documentation/locking/ww-mutex-design.txt |
5060 | serge | 39 | * |
40 | * The basic usage pattern is to: |
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41 | * |
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42 | * drm_modeset_acquire_init(&ctx) |
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43 | * retry: |
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44 | * foreach (lock in random_ordered_set_of_locks) { |
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45 | * ret = drm_modeset_lock(lock, &ctx) |
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46 | * if (ret == -EDEADLK) { |
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47 | * drm_modeset_backoff(&ctx); |
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48 | * goto retry; |
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49 | * } |
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50 | * } |
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51 | * |
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52 | * ... do stuff ... |
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53 | * |
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54 | * drm_modeset_drop_locks(&ctx); |
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55 | * drm_modeset_acquire_fini(&ctx); |
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56 | */ |
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57 | |||
58 | |||
59 | /** |
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5271 | serge | 60 | * __drm_modeset_lock_all - internal helper to grab all modeset locks |
61 | * @dev: DRM device |
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62 | * @trylock: trylock mode for atomic contexts |
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63 | * |
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64 | * This is a special version of drm_modeset_lock_all() which can also be used in |
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65 | * atomic contexts. Then @trylock must be set to true. |
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66 | * |
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67 | * Returns: |
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68 | * 0 on success or negative error code on failure. |
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69 | */ |
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70 | int __drm_modeset_lock_all(struct drm_device *dev, |
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71 | bool trylock) |
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72 | { |
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73 | struct drm_mode_config *config = &dev->mode_config; |
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74 | struct drm_modeset_acquire_ctx *ctx; |
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75 | int ret; |
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76 | |||
77 | ctx = kzalloc(sizeof(*ctx), |
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78 | trylock ? GFP_ATOMIC : GFP_KERNEL); |
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79 | if (!ctx) |
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80 | return -ENOMEM; |
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81 | |||
82 | if (trylock) { |
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83 | if (!mutex_trylock(&config->mutex)) |
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84 | return -EBUSY; |
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85 | } else { |
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86 | mutex_lock(&config->mutex); |
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87 | } |
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88 | |||
89 | drm_modeset_acquire_init(ctx, 0); |
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90 | ctx->trylock_only = trylock; |
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91 | |||
92 | retry: |
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93 | ret = drm_modeset_lock(&config->connection_mutex, ctx); |
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94 | if (ret) |
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95 | goto fail; |
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96 | ret = drm_modeset_lock_all_crtcs(dev, ctx); |
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97 | if (ret) |
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98 | goto fail; |
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99 | |||
100 | WARN_ON(config->acquire_ctx); |
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101 | |||
102 | /* now we hold the locks, so now that it is safe, stash the |
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103 | * ctx for drm_modeset_unlock_all(): |
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104 | */ |
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105 | config->acquire_ctx = ctx; |
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106 | |||
107 | drm_warn_on_modeset_not_all_locked(dev); |
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108 | |||
109 | return 0; |
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110 | |||
111 | fail: |
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112 | if (ret == -EDEADLK) { |
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113 | drm_modeset_backoff(ctx); |
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114 | goto retry; |
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115 | } |
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116 | |||
117 | return ret; |
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118 | } |
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119 | EXPORT_SYMBOL(__drm_modeset_lock_all); |
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120 | |||
121 | /** |
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122 | * drm_modeset_lock_all - take all modeset locks |
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123 | * @dev: drm device |
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124 | * |
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125 | * This function takes all modeset locks, suitable where a more fine-grained |
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126 | * scheme isn't (yet) implemented. Locks must be dropped with |
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127 | * drm_modeset_unlock_all. |
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128 | */ |
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129 | void drm_modeset_lock_all(struct drm_device *dev) |
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130 | { |
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131 | WARN_ON(__drm_modeset_lock_all(dev, false) != 0); |
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132 | } |
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133 | EXPORT_SYMBOL(drm_modeset_lock_all); |
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134 | |||
135 | /** |
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136 | * drm_modeset_unlock_all - drop all modeset locks |
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137 | * @dev: device |
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138 | * |
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139 | * This function drop all modeset locks taken by drm_modeset_lock_all. |
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140 | */ |
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141 | void drm_modeset_unlock_all(struct drm_device *dev) |
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142 | { |
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143 | struct drm_mode_config *config = &dev->mode_config; |
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144 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; |
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145 | |||
146 | if (WARN_ON(!ctx)) |
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147 | return; |
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148 | |||
149 | config->acquire_ctx = NULL; |
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150 | drm_modeset_drop_locks(ctx); |
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151 | drm_modeset_acquire_fini(ctx); |
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152 | |||
153 | kfree(ctx); |
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154 | |||
155 | mutex_unlock(&dev->mode_config.mutex); |
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156 | } |
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157 | EXPORT_SYMBOL(drm_modeset_unlock_all); |
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158 | |||
159 | /** |
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160 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
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161 | * @crtc: DRM CRTC |
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162 | * @plane: DRM plane to be updated on @crtc |
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163 | * |
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164 | * This function locks the given crtc and plane (which should be either the |
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165 | * primary or cursor plane) using a hidden acquire context. This is necessary so |
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166 | * that drivers internally using the atomic interfaces can grab further locks |
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167 | * with the lock acquire context. |
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168 | * |
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169 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
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170 | * converted to universal planes yet. |
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171 | */ |
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172 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
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173 | struct drm_plane *plane) |
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174 | { |
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175 | struct drm_modeset_acquire_ctx *ctx; |
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176 | int ret; |
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177 | |||
178 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
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179 | if (WARN_ON(!ctx)) |
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180 | return; |
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181 | |||
182 | drm_modeset_acquire_init(ctx, 0); |
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183 | |||
184 | retry: |
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185 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
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186 | if (ret) |
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187 | goto fail; |
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188 | |||
189 | if (plane) { |
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190 | ret = drm_modeset_lock(&plane->mutex, ctx); |
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191 | if (ret) |
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192 | goto fail; |
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193 | |||
194 | if (plane->crtc) { |
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195 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); |
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196 | if (ret) |
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197 | goto fail; |
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198 | } |
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199 | } |
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200 | |||
201 | WARN_ON(crtc->acquire_ctx); |
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202 | |||
203 | /* now we hold the locks, so now that it is safe, stash the |
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204 | * ctx for drm_modeset_unlock_crtc(): |
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205 | */ |
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206 | crtc->acquire_ctx = ctx; |
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207 | |||
208 | return; |
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209 | |||
210 | fail: |
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211 | if (ret == -EDEADLK) { |
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212 | drm_modeset_backoff(ctx); |
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213 | goto retry; |
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214 | } |
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215 | } |
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216 | EXPORT_SYMBOL(drm_modeset_lock_crtc); |
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217 | |||
218 | /** |
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219 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls |
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220 | * @crtc: drm crtc |
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221 | * |
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222 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc |
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223 | * locking, and store the acquire ctx in the corresponding crtc. All other |
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224 | * legacy operations take all locks and use a global acquire context. This |
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225 | * function grabs the right one. |
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226 | */ |
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227 | struct drm_modeset_acquire_ctx * |
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228 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) |
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229 | { |
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230 | if (crtc->acquire_ctx) |
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231 | return crtc->acquire_ctx; |
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232 | |||
233 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); |
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234 | |||
235 | return crtc->dev->mode_config.acquire_ctx; |
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236 | } |
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237 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); |
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238 | |||
239 | /** |
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240 | * drm_modeset_unlock_crtc - drop crtc lock |
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241 | * @crtc: drm crtc |
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242 | * |
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243 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other |
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244 | * locks acquired through the hidden context. |
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245 | */ |
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246 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) |
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247 | { |
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248 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; |
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249 | |||
250 | if (WARN_ON(!ctx)) |
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251 | return; |
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252 | |||
253 | crtc->acquire_ctx = NULL; |
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254 | drm_modeset_drop_locks(ctx); |
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255 | drm_modeset_acquire_fini(ctx); |
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256 | |||
257 | kfree(ctx); |
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258 | } |
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259 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); |
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260 | |||
261 | /** |
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262 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked |
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263 | * @dev: device |
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264 | * |
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265 | * Useful as a debug assert. |
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266 | */ |
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267 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) |
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268 | { |
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269 | struct drm_crtc *crtc; |
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270 | |||
271 | /* Locking is currently fubar in the panic handler. */ |
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272 | // if (oops_in_progress) |
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273 | // return; |
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274 | |||
275 | list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) |
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276 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
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277 | |||
278 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); |
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279 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); |
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280 | } |
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281 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); |
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282 | |||
283 | /** |
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5060 | serge | 284 | * drm_modeset_acquire_init - initialize acquire context |
285 | * @ctx: the acquire context |
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286 | * @flags: for future |
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287 | */ |
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288 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, |
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289 | uint32_t flags) |
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290 | { |
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291 | memset(ctx, 0, sizeof(*ctx)); |
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292 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
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293 | INIT_LIST_HEAD(&ctx->locked); |
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294 | } |
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295 | EXPORT_SYMBOL(drm_modeset_acquire_init); |
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296 | |||
297 | /** |
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298 | * drm_modeset_acquire_fini - cleanup acquire context |
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299 | * @ctx: the acquire context |
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300 | */ |
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301 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) |
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302 | { |
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303 | ww_acquire_fini(&ctx->ww_ctx); |
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304 | } |
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305 | EXPORT_SYMBOL(drm_modeset_acquire_fini); |
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306 | |||
307 | /** |
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308 | * drm_modeset_drop_locks - drop all locks |
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309 | * @ctx: the acquire context |
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310 | * |
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311 | * Drop all locks currently held against this acquire context. |
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312 | */ |
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313 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) |
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314 | { |
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315 | WARN_ON(ctx->contended); |
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316 | while (!list_empty(&ctx->locked)) { |
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317 | struct drm_modeset_lock *lock; |
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318 | |||
319 | lock = list_first_entry(&ctx->locked, |
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320 | struct drm_modeset_lock, head); |
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321 | |||
322 | drm_modeset_unlock(lock); |
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323 | } |
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324 | } |
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325 | EXPORT_SYMBOL(drm_modeset_drop_locks); |
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326 | |||
327 | static inline int modeset_lock(struct drm_modeset_lock *lock, |
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328 | struct drm_modeset_acquire_ctx *ctx, |
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329 | bool interruptible, bool slow) |
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330 | { |
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331 | int ret; |
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332 | |||
333 | WARN_ON(ctx->contended); |
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334 | |||
5271 | serge | 335 | if (ctx->trylock_only) { |
336 | if (!ww_mutex_trylock(&lock->mutex)) |
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337 | return -EBUSY; |
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338 | else |
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339 | return 0; |
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340 | } else if (interruptible && slow) { |
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5060 | serge | 341 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
342 | } else if (interruptible) { |
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343 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); |
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344 | } else if (slow) { |
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345 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); |
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346 | ret = 0; |
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347 | } else { |
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348 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); |
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349 | } |
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350 | if (!ret) { |
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351 | WARN_ON(!list_empty(&lock->head)); |
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352 | list_add(&lock->head, &ctx->locked); |
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353 | } else if (ret == -EALREADY) { |
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354 | /* we already hold the lock.. this is fine. For atomic |
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355 | * we will need to be able to drm_modeset_lock() things |
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356 | * without having to keep track of what is already locked |
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357 | * or not. |
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358 | */ |
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359 | ret = 0; |
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360 | } else if (ret == -EDEADLK) { |
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361 | ctx->contended = lock; |
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362 | } |
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363 | |||
364 | return ret; |
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365 | } |
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366 | |||
367 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, |
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368 | bool interruptible) |
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369 | { |
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370 | struct drm_modeset_lock *contended = ctx->contended; |
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371 | |||
372 | ctx->contended = NULL; |
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373 | |||
374 | if (WARN_ON(!contended)) |
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375 | return 0; |
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376 | |||
377 | drm_modeset_drop_locks(ctx); |
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378 | |||
379 | return modeset_lock(contended, ctx, interruptible, true); |
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380 | } |
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381 | |||
382 | /** |
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383 | * drm_modeset_backoff - deadlock avoidance backoff |
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384 | * @ctx: the acquire context |
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385 | * |
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386 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), |
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387 | * you must call this function to drop all currently held locks and |
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388 | * block until the contended lock becomes available. |
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389 | */ |
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390 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) |
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391 | { |
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392 | modeset_backoff(ctx, false); |
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393 | } |
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394 | EXPORT_SYMBOL(drm_modeset_backoff); |
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395 | |||
396 | /** |
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397 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff |
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398 | * @ctx: the acquire context |
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399 | * |
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400 | * Interruptible version of drm_modeset_backoff() |
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401 | */ |
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402 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) |
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403 | { |
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404 | return modeset_backoff(ctx, true); |
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405 | } |
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406 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); |
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407 | |||
408 | /** |
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409 | * drm_modeset_lock - take modeset lock |
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410 | * @lock: lock to take |
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411 | * @ctx: acquire ctx |
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412 | * |
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413 | * If ctx is not NULL, then its ww acquire context is used and the |
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414 | * lock will be tracked by the context and can be released by calling |
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415 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a |
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416 | * deadlock scenario has been detected and it is an error to attempt |
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417 | * to take any more locks without first calling drm_modeset_backoff(). |
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418 | */ |
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419 | int drm_modeset_lock(struct drm_modeset_lock *lock, |
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420 | struct drm_modeset_acquire_ctx *ctx) |
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421 | { |
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422 | if (ctx) |
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423 | return modeset_lock(lock, ctx, false, false); |
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424 | |||
425 | ww_mutex_lock(&lock->mutex, NULL); |
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426 | return 0; |
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427 | } |
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428 | EXPORT_SYMBOL(drm_modeset_lock); |
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429 | |||
430 | /** |
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431 | * drm_modeset_lock_interruptible - take modeset lock |
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432 | * @lock: lock to take |
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433 | * @ctx: acquire ctx |
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434 | * |
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435 | * Interruptible version of drm_modeset_lock() |
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436 | */ |
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437 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, |
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438 | struct drm_modeset_acquire_ctx *ctx) |
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439 | { |
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440 | if (ctx) |
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441 | return modeset_lock(lock, ctx, true, false); |
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442 | |||
443 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); |
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444 | } |
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445 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); |
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446 | |||
447 | /** |
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448 | * drm_modeset_unlock - drop modeset lock |
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449 | * @lock: lock to release |
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450 | */ |
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451 | void drm_modeset_unlock(struct drm_modeset_lock *lock) |
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452 | { |
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453 | list_del_init(&lock->head); |
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454 | ww_mutex_unlock(&lock->mutex); |
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455 | } |
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456 | EXPORT_SYMBOL(drm_modeset_unlock); |
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457 | |||
5271 | serge | 458 | /* In some legacy codepaths it's convenient to just grab all the crtc and plane |
459 | * related locks. */ |
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5060 | serge | 460 | int drm_modeset_lock_all_crtcs(struct drm_device *dev, |
461 | struct drm_modeset_acquire_ctx *ctx) |
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462 | { |
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463 | struct drm_mode_config *config = &dev->mode_config; |
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464 | struct drm_crtc *crtc; |
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5271 | serge | 465 | struct drm_plane *plane; |
5060 | serge | 466 | int ret = 0; |
467 | |||
468 | list_for_each_entry(crtc, &config->crtc_list, head) { |
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469 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
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470 | if (ret) |
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471 | return ret; |
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472 | } |
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473 | |||
5271 | serge | 474 | list_for_each_entry(plane, &config->plane_list, head) { |
475 | ret = drm_modeset_lock(&plane->mutex, ctx); |
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476 | if (ret) |
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477 | return ret; |
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478 | } |
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479 | |||
5060 | serge | 480 | return 0; |
481 | } |
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482 | EXPORT_SYMBOL(drm_modeset_lock_all_crtcs); |