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Rev | Author | Line No. | Line |
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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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7144 | serge | 43 | * retry: |
5060 | serge | 44 | * foreach (lock in random_ordered_set_of_locks) { |
7144 | serge | 45 | * ret = drm_modeset_lock(lock, &ctx) |
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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5060 | serge | 50 | * } |
51 | * ... do stuff ... |
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52 | * drm_modeset_drop_locks(&ctx); |
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53 | * drm_modeset_acquire_fini(&ctx); |
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54 | */ |
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55 | |||
56 | /** |
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6084 | serge | 57 | * drm_modeset_lock_all - take all modeset locks |
6937 | serge | 58 | * @dev: DRM device |
5271 | serge | 59 | * |
6084 | serge | 60 | * This function takes all modeset locks, suitable where a more fine-grained |
6937 | serge | 61 | * scheme isn't (yet) implemented. Locks must be dropped by calling the |
62 | * drm_modeset_unlock_all() function. |
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63 | * |
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64 | * This function is deprecated. It allocates a lock acquisition context and |
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65 | * stores it in the DRM device's ->mode_config. This facilitate conversion of |
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66 | * existing code because it removes the need to manually deal with the |
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67 | * acquisition context, but it is also brittle because the context is global |
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68 | * and care must be taken not to nest calls. New code should use the |
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69 | * drm_modeset_lock_all_ctx() function and pass in the context explicitly. |
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5271 | serge | 70 | */ |
6084 | serge | 71 | void drm_modeset_lock_all(struct drm_device *dev) |
5271 | serge | 72 | { |
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 | |||
6084 | serge | 77 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
78 | if (WARN_ON(!ctx)) |
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79 | return; |
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5271 | serge | 80 | |
6084 | serge | 81 | mutex_lock(&config->mutex); |
5271 | serge | 82 | |
83 | drm_modeset_acquire_init(ctx, 0); |
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84 | |||
85 | retry: |
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6937 | serge | 86 | ret = drm_modeset_lock_all_ctx(dev, ctx); |
87 | if (ret < 0) { |
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88 | if (ret == -EDEADLK) { |
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89 | drm_modeset_backoff(ctx); |
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90 | goto retry; |
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91 | } |
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5271 | serge | 92 | |
6937 | serge | 93 | drm_modeset_acquire_fini(ctx); |
94 | kfree(ctx); |
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95 | return; |
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96 | } |
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97 | |||
5271 | serge | 98 | WARN_ON(config->acquire_ctx); |
99 | |||
6937 | serge | 100 | /* |
101 | * We hold the locks now, so it is safe to stash the acquisition |
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102 | * context for drm_modeset_unlock_all(). |
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5271 | serge | 103 | */ |
104 | config->acquire_ctx = ctx; |
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105 | |||
106 | drm_warn_on_modeset_not_all_locked(dev); |
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107 | } |
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108 | EXPORT_SYMBOL(drm_modeset_lock_all); |
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109 | |||
110 | /** |
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111 | * drm_modeset_unlock_all - drop all modeset locks |
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6937 | serge | 112 | * @dev: DRM device |
5271 | serge | 113 | * |
6937 | serge | 114 | * This function drops all modeset locks taken by a previous call to the |
115 | * drm_modeset_lock_all() function. |
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116 | * |
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117 | * This function is deprecated. It uses the lock acquisition context stored |
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118 | * in the DRM device's ->mode_config. This facilitates conversion of existing |
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119 | * code because it removes the need to manually deal with the acquisition |
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120 | * context, but it is also brittle because the context is global and care must |
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121 | * be taken not to nest calls. New code should pass the acquisition context |
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122 | * directly to the drm_modeset_drop_locks() function. |
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5271 | serge | 123 | */ |
124 | void drm_modeset_unlock_all(struct drm_device *dev) |
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125 | { |
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126 | struct drm_mode_config *config = &dev->mode_config; |
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127 | struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx; |
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128 | |||
129 | if (WARN_ON(!ctx)) |
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130 | return; |
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131 | |||
132 | config->acquire_ctx = NULL; |
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133 | drm_modeset_drop_locks(ctx); |
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134 | drm_modeset_acquire_fini(ctx); |
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135 | |||
136 | kfree(ctx); |
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137 | |||
138 | mutex_unlock(&dev->mode_config.mutex); |
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139 | } |
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140 | EXPORT_SYMBOL(drm_modeset_unlock_all); |
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141 | |||
142 | /** |
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143 | * drm_modeset_lock_crtc - lock crtc with hidden acquire ctx for a plane update |
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144 | * @crtc: DRM CRTC |
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145 | * @plane: DRM plane to be updated on @crtc |
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146 | * |
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147 | * This function locks the given crtc and plane (which should be either the |
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148 | * primary or cursor plane) using a hidden acquire context. This is necessary so |
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149 | * that drivers internally using the atomic interfaces can grab further locks |
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150 | * with the lock acquire context. |
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151 | * |
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152 | * Note that @plane can be NULL, e.g. when the cursor support hasn't yet been |
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153 | * converted to universal planes yet. |
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154 | */ |
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155 | void drm_modeset_lock_crtc(struct drm_crtc *crtc, |
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156 | struct drm_plane *plane) |
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157 | { |
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158 | struct drm_modeset_acquire_ctx *ctx; |
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159 | int ret; |
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160 | |||
161 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
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162 | if (WARN_ON(!ctx)) |
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163 | return; |
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164 | |||
165 | drm_modeset_acquire_init(ctx, 0); |
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166 | |||
167 | retry: |
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168 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
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169 | if (ret) |
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170 | goto fail; |
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171 | |||
172 | if (plane) { |
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173 | ret = drm_modeset_lock(&plane->mutex, ctx); |
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174 | if (ret) |
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175 | goto fail; |
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176 | |||
177 | if (plane->crtc) { |
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178 | ret = drm_modeset_lock(&plane->crtc->mutex, ctx); |
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179 | if (ret) |
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180 | goto fail; |
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181 | } |
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182 | } |
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183 | |||
184 | WARN_ON(crtc->acquire_ctx); |
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185 | |||
186 | /* now we hold the locks, so now that it is safe, stash the |
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187 | * ctx for drm_modeset_unlock_crtc(): |
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188 | */ |
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189 | crtc->acquire_ctx = ctx; |
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190 | |||
191 | return; |
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192 | |||
193 | fail: |
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194 | if (ret == -EDEADLK) { |
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195 | drm_modeset_backoff(ctx); |
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196 | goto retry; |
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197 | } |
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198 | } |
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199 | EXPORT_SYMBOL(drm_modeset_lock_crtc); |
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200 | |||
201 | /** |
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202 | * drm_modeset_legacy_acquire_ctx - find acquire ctx for legacy ioctls |
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203 | * @crtc: drm crtc |
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204 | * |
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205 | * Legacy ioctl operations like cursor updates or page flips only have per-crtc |
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206 | * locking, and store the acquire ctx in the corresponding crtc. All other |
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207 | * legacy operations take all locks and use a global acquire context. This |
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208 | * function grabs the right one. |
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209 | */ |
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210 | struct drm_modeset_acquire_ctx * |
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211 | drm_modeset_legacy_acquire_ctx(struct drm_crtc *crtc) |
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212 | { |
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213 | if (crtc->acquire_ctx) |
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214 | return crtc->acquire_ctx; |
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215 | |||
216 | WARN_ON(!crtc->dev->mode_config.acquire_ctx); |
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217 | |||
218 | return crtc->dev->mode_config.acquire_ctx; |
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219 | } |
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220 | EXPORT_SYMBOL(drm_modeset_legacy_acquire_ctx); |
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221 | |||
222 | /** |
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223 | * drm_modeset_unlock_crtc - drop crtc lock |
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224 | * @crtc: drm crtc |
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225 | * |
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226 | * This drops the crtc lock acquire with drm_modeset_lock_crtc() and all other |
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227 | * locks acquired through the hidden context. |
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228 | */ |
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229 | void drm_modeset_unlock_crtc(struct drm_crtc *crtc) |
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230 | { |
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231 | struct drm_modeset_acquire_ctx *ctx = crtc->acquire_ctx; |
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232 | |||
233 | if (WARN_ON(!ctx)) |
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234 | return; |
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235 | |||
236 | crtc->acquire_ctx = NULL; |
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237 | drm_modeset_drop_locks(ctx); |
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238 | drm_modeset_acquire_fini(ctx); |
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239 | |||
240 | kfree(ctx); |
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241 | } |
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242 | EXPORT_SYMBOL(drm_modeset_unlock_crtc); |
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243 | |||
244 | /** |
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245 | * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked |
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246 | * @dev: device |
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247 | * |
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248 | * Useful as a debug assert. |
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249 | */ |
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250 | void drm_warn_on_modeset_not_all_locked(struct drm_device *dev) |
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251 | { |
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252 | struct drm_crtc *crtc; |
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253 | |||
254 | /* Locking is currently fubar in the panic handler. */ |
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6084 | serge | 255 | if (oops_in_progress) |
256 | return; |
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5271 | serge | 257 | |
6084 | serge | 258 | drm_for_each_crtc(crtc, dev) |
5271 | serge | 259 | WARN_ON(!drm_modeset_is_locked(&crtc->mutex)); |
260 | |||
261 | WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); |
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262 | WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); |
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263 | } |
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264 | EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked); |
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265 | |||
266 | /** |
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5060 | serge | 267 | * drm_modeset_acquire_init - initialize acquire context |
268 | * @ctx: the acquire context |
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269 | * @flags: for future |
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270 | */ |
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271 | void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, |
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272 | uint32_t flags) |
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273 | { |
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274 | memset(ctx, 0, sizeof(*ctx)); |
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275 | ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class); |
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276 | INIT_LIST_HEAD(&ctx->locked); |
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277 | } |
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278 | EXPORT_SYMBOL(drm_modeset_acquire_init); |
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279 | |||
280 | /** |
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281 | * drm_modeset_acquire_fini - cleanup acquire context |
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282 | * @ctx: the acquire context |
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283 | */ |
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284 | void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx) |
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285 | { |
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286 | ww_acquire_fini(&ctx->ww_ctx); |
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287 | } |
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288 | EXPORT_SYMBOL(drm_modeset_acquire_fini); |
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289 | |||
290 | /** |
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291 | * drm_modeset_drop_locks - drop all locks |
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292 | * @ctx: the acquire context |
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293 | * |
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294 | * Drop all locks currently held against this acquire context. |
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295 | */ |
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296 | void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx) |
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297 | { |
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298 | WARN_ON(ctx->contended); |
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299 | while (!list_empty(&ctx->locked)) { |
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300 | struct drm_modeset_lock *lock; |
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301 | |||
302 | lock = list_first_entry(&ctx->locked, |
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303 | struct drm_modeset_lock, head); |
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304 | |||
305 | drm_modeset_unlock(lock); |
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306 | } |
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307 | } |
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308 | EXPORT_SYMBOL(drm_modeset_drop_locks); |
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309 | |||
310 | static inline int modeset_lock(struct drm_modeset_lock *lock, |
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311 | struct drm_modeset_acquire_ctx *ctx, |
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312 | bool interruptible, bool slow) |
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313 | { |
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314 | int ret; |
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315 | |||
316 | WARN_ON(ctx->contended); |
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317 | |||
5271 | serge | 318 | if (ctx->trylock_only) { |
6084 | serge | 319 | lockdep_assert_held(&ctx->ww_ctx); |
320 | |||
5271 | serge | 321 | if (!ww_mutex_trylock(&lock->mutex)) |
322 | return -EBUSY; |
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323 | else |
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324 | return 0; |
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325 | } else if (interruptible && slow) { |
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5060 | serge | 326 | ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx); |
327 | } else if (interruptible) { |
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328 | ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx); |
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329 | } else if (slow) { |
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330 | ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx); |
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331 | ret = 0; |
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332 | } else { |
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333 | ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx); |
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334 | } |
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335 | if (!ret) { |
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336 | WARN_ON(!list_empty(&lock->head)); |
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337 | list_add(&lock->head, &ctx->locked); |
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338 | } else if (ret == -EALREADY) { |
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339 | /* we already hold the lock.. this is fine. For atomic |
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340 | * we will need to be able to drm_modeset_lock() things |
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341 | * without having to keep track of what is already locked |
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342 | * or not. |
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343 | */ |
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344 | ret = 0; |
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345 | } else if (ret == -EDEADLK) { |
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346 | ctx->contended = lock; |
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347 | } |
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348 | |||
349 | return ret; |
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350 | } |
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351 | |||
352 | static int modeset_backoff(struct drm_modeset_acquire_ctx *ctx, |
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353 | bool interruptible) |
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354 | { |
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355 | struct drm_modeset_lock *contended = ctx->contended; |
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356 | |||
357 | ctx->contended = NULL; |
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358 | |||
359 | if (WARN_ON(!contended)) |
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360 | return 0; |
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361 | |||
362 | drm_modeset_drop_locks(ctx); |
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363 | |||
364 | return modeset_lock(contended, ctx, interruptible, true); |
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365 | } |
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366 | |||
367 | /** |
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368 | * drm_modeset_backoff - deadlock avoidance backoff |
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369 | * @ctx: the acquire context |
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370 | * |
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371 | * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK), |
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372 | * you must call this function to drop all currently held locks and |
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373 | * block until the contended lock becomes available. |
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374 | */ |
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375 | void drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx) |
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376 | { |
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377 | modeset_backoff(ctx, false); |
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378 | } |
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379 | EXPORT_SYMBOL(drm_modeset_backoff); |
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380 | |||
381 | /** |
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382 | * drm_modeset_backoff_interruptible - deadlock avoidance backoff |
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383 | * @ctx: the acquire context |
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384 | * |
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385 | * Interruptible version of drm_modeset_backoff() |
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386 | */ |
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387 | int drm_modeset_backoff_interruptible(struct drm_modeset_acquire_ctx *ctx) |
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388 | { |
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389 | return modeset_backoff(ctx, true); |
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390 | } |
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391 | EXPORT_SYMBOL(drm_modeset_backoff_interruptible); |
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392 | |||
393 | /** |
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394 | * drm_modeset_lock - take modeset lock |
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395 | * @lock: lock to take |
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396 | * @ctx: acquire ctx |
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397 | * |
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398 | * If ctx is not NULL, then its ww acquire context is used and the |
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399 | * lock will be tracked by the context and can be released by calling |
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400 | * drm_modeset_drop_locks(). If -EDEADLK is returned, this means a |
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401 | * deadlock scenario has been detected and it is an error to attempt |
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402 | * to take any more locks without first calling drm_modeset_backoff(). |
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403 | */ |
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404 | int drm_modeset_lock(struct drm_modeset_lock *lock, |
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405 | struct drm_modeset_acquire_ctx *ctx) |
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406 | { |
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407 | if (ctx) |
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408 | return modeset_lock(lock, ctx, false, false); |
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409 | |||
410 | ww_mutex_lock(&lock->mutex, NULL); |
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411 | return 0; |
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412 | } |
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413 | EXPORT_SYMBOL(drm_modeset_lock); |
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414 | |||
415 | /** |
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416 | * drm_modeset_lock_interruptible - take modeset lock |
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417 | * @lock: lock to take |
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418 | * @ctx: acquire ctx |
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419 | * |
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420 | * Interruptible version of drm_modeset_lock() |
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421 | */ |
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422 | int drm_modeset_lock_interruptible(struct drm_modeset_lock *lock, |
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423 | struct drm_modeset_acquire_ctx *ctx) |
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424 | { |
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425 | if (ctx) |
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426 | return modeset_lock(lock, ctx, true, false); |
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427 | |||
428 | return ww_mutex_lock_interruptible(&lock->mutex, NULL); |
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429 | } |
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430 | EXPORT_SYMBOL(drm_modeset_lock_interruptible); |
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431 | |||
432 | /** |
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433 | * drm_modeset_unlock - drop modeset lock |
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434 | * @lock: lock to release |
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435 | */ |
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436 | void drm_modeset_unlock(struct drm_modeset_lock *lock) |
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437 | { |
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438 | list_del_init(&lock->head); |
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439 | ww_mutex_unlock(&lock->mutex); |
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440 | } |
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441 | EXPORT_SYMBOL(drm_modeset_unlock); |
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442 | |||
6937 | serge | 443 | /** |
444 | * drm_modeset_lock_all_ctx - take all modeset locks |
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445 | * @dev: DRM device |
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446 | * @ctx: lock acquisition context |
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447 | * |
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448 | * This function takes all modeset locks, suitable where a more fine-grained |
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449 | * scheme isn't (yet) implemented. |
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450 | * |
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451 | * Unlike drm_modeset_lock_all(), it doesn't take the dev->mode_config.mutex |
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452 | * since that lock isn't required for modeset state changes. Callers which |
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453 | * need to grab that lock too need to do so outside of the acquire context |
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454 | * @ctx. |
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455 | * |
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456 | * Locks acquired with this function should be released by calling the |
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457 | * drm_modeset_drop_locks() function on @ctx. |
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458 | * |
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459 | * Returns: 0 on success or a negative error-code on failure. |
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460 | */ |
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461 | int drm_modeset_lock_all_ctx(struct drm_device *dev, |
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7144 | serge | 462 | struct drm_modeset_acquire_ctx *ctx) |
5060 | serge | 463 | { |
464 | struct drm_crtc *crtc; |
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5271 | serge | 465 | struct drm_plane *plane; |
6937 | serge | 466 | int ret; |
5060 | serge | 467 | |
6937 | serge | 468 | ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx); |
469 | if (ret) |
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470 | return ret; |
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471 | |||
6084 | serge | 472 | drm_for_each_crtc(crtc, dev) { |
5060 | serge | 473 | ret = drm_modeset_lock(&crtc->mutex, ctx); |
474 | if (ret) |
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475 | return ret; |
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476 | } |
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477 | |||
6084 | serge | 478 | drm_for_each_plane(plane, dev) { |
5271 | serge | 479 | ret = drm_modeset_lock(&plane->mutex, ctx); |
480 | if (ret) |
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481 | return ret; |
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482 | } |
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483 | |||
5060 | serge | 484 | return 0; |
485 | } |
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6937 | serge | 486 | EXPORT_SYMBOL(drm_modeset_lock_all_ctx);> |