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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 | /** |
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6084 | serge | 59 | * drm_modeset_lock_all - take all modeset locks |
60 | * @dev: drm device |
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5271 | serge | 61 | * |
6084 | serge | 62 | * This function takes all modeset locks, suitable where a more fine-grained |
63 | * scheme isn't (yet) implemented. Locks must be dropped with |
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64 | * drm_modeset_unlock_all. |
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5271 | serge | 65 | */ |
6084 | serge | 66 | void drm_modeset_lock_all(struct drm_device *dev) |
5271 | serge | 67 | { |
68 | struct drm_mode_config *config = &dev->mode_config; |
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69 | struct drm_modeset_acquire_ctx *ctx; |
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70 | int ret; |
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71 | |||
6084 | serge | 72 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
73 | if (WARN_ON(!ctx)) |
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74 | return; |
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5271 | serge | 75 | |
6084 | serge | 76 | mutex_lock(&config->mutex); |
5271 | serge | 77 | |
78 | drm_modeset_acquire_init(ctx, 0); |
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79 | |||
80 | retry: |
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81 | ret = drm_modeset_lock(&config->connection_mutex, ctx); |
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82 | if (ret) |
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83 | goto fail; |
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84 | ret = drm_modeset_lock_all_crtcs(dev, ctx); |
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85 | if (ret) |
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86 | goto fail; |
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87 | |||
88 | WARN_ON(config->acquire_ctx); |
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89 | |||
90 | /* now we hold the locks, so now that it is safe, stash the |
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91 | * ctx for drm_modeset_unlock_all(): |
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92 | */ |
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93 | config->acquire_ctx = ctx; |
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94 | |||
95 | drm_warn_on_modeset_not_all_locked(dev); |
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96 | |||
6084 | serge | 97 | return; |
5271 | serge | 98 | |
99 | fail: |
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100 | if (ret == -EDEADLK) { |
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101 | drm_modeset_backoff(ctx); |
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102 | goto retry; |
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103 | } |
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104 | |||
6084 | serge | 105 | kfree(ctx); |
5271 | serge | 106 | } |
107 | EXPORT_SYMBOL(drm_modeset_lock_all); |
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108 | |||
109 | /** |
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110 | * drm_modeset_unlock_all - drop all modeset locks |
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111 | * @dev: device |
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112 | * |
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113 | * This function drop all modeset locks taken by drm_modeset_lock_all. |
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114 | */ |
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115 | void drm_modeset_unlock_all(struct drm_device *dev) |
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116 | { |
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117 | struct drm_mode_config *config = &dev->mode_config; |
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118 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; |
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119 | |||
120 | if (WARN_ON(!ctx)) |
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121 | return; |
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122 | |||
123 | config->acquire_ctx = NULL; |
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124 | drm_modeset_drop_locks(ctx); |
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125 | drm_modeset_acquire_fini(ctx); |
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126 | |||
127 | kfree(ctx); |
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128 | |||
129 | mutex_unlock(&dev->mode_config.mutex); |
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130 | } |
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131 | EXPORT_SYMBOL(drm_modeset_unlock_all); |
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132 | |||
133 | /** |
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134 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
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135 | * @crtc: DRM CRTC |
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136 | * @plane: DRM plane to be updated on @crtc |
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137 | * |
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138 | * This function locks the given crtc and plane (which should be either the |
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139 | * primary or cursor plane) using a hidden acquire context. This is necessary so |
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140 | * that drivers internally using the atomic interfaces can grab further locks |
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141 | * with the lock acquire context. |
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142 | * |
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143 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
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144 | * converted to universal planes yet. |
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145 | */ |
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146 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
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147 | struct drm_plane *plane) |
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148 | { |
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149 | struct drm_modeset_acquire_ctx *ctx; |
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150 | int ret; |
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151 | |||
152 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
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153 | if (WARN_ON(!ctx)) |
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154 | return; |
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155 | |||
156 | drm_modeset_acquire_init(ctx, 0); |
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157 | |||
158 | retry: |
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159 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
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160 | if (ret) |
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161 | goto fail; |
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162 | |||
163 | if (plane) { |
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164 | ret = drm_modeset_lock(&plane->mutex, ctx); |
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165 | if (ret) |
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166 | goto fail; |
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167 | |||
168 | if (plane->crtc) { |
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169 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); |
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170 | if (ret) |
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171 | goto fail; |
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172 | } |
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173 | } |
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174 | |||
175 | WARN_ON(crtc->acquire_ctx); |
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176 | |||
177 | /* now we hold the locks, so now that it is safe, stash the |
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178 | * ctx for drm_modeset_unlock_crtc(): |
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179 | */ |
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180 | crtc->acquire_ctx = ctx; |
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181 | |||
182 | return; |
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183 | |||
184 | fail: |
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185 | if (ret == -EDEADLK) { |
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186 | drm_modeset_backoff(ctx); |
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187 | goto retry; |
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188 | } |
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189 | } |
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190 | EXPORT_SYMBOL(drm_modeset_lock_crtc); |
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191 | |||
192 | /** |
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193 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls |
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194 | * @crtc: drm crtc |
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195 | * |
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196 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc |
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197 | * locking, and store the acquire ctx in the corresponding crtc. All other |
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198 | * legacy operations take all locks and use a global acquire context. This |
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199 | * function grabs the right one. |
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200 | */ |
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201 | struct drm_modeset_acquire_ctx * |
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202 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) |
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203 | { |
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204 | if (crtc->acquire_ctx) |
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205 | return crtc->acquire_ctx; |
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206 | |||
207 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); |
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208 | |||
209 | return crtc->dev->mode_config.acquire_ctx; |
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210 | } |
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211 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); |
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212 | |||
213 | /** |
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214 | * drm_modeset_unlock_crtc - drop crtc lock |
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215 | * @crtc: drm crtc |
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216 | * |
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217 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other |
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218 | * locks acquired through the hidden context. |
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219 | */ |
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220 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) |
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221 | { |
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222 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; |
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223 | |||
224 | if (WARN_ON(!ctx)) |
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225 | return; |
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226 | |||
227 | crtc->acquire_ctx = NULL; |
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228 | drm_modeset_drop_locks(ctx); |
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229 | drm_modeset_acquire_fini(ctx); |
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230 | |||
231 | kfree(ctx); |
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232 | } |
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233 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); |
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234 | |||
235 | /** |
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236 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked |
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237 | * @dev: device |
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238 | * |
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239 | * Useful as a debug assert. |
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240 | */ |
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241 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) |
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242 | { |
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243 | struct drm_crtc *crtc; |
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244 | |||
245 | /* Locking is currently fubar in the panic handler. */ |
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6084 | serge | 246 | if (oops_in_progress) |
247 | return; |
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5271 | serge | 248 | |
6084 | serge | 249 | drm_for_each_crtc(crtc, dev) |
5271 | serge | 250 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
251 | |||
252 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); |
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253 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); |
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254 | } |
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255 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); |
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256 |