1 /* 2 * Copyright (C) 2014 Red Hat 3 * Author: Rob Clark <robdclark@gmail.com> 4 * 5 * Permission is hereby granted, free of charge, to any person obtaining a 6 * copy of this software and associated documentation files (the "Software"), 7 * to deal in the Software without restriction, including without limitation 8 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 9 * and/or sell copies of the Software, and to permit persons to whom the 10 * Software is furnished to do so, subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be included in 13 * all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR 19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 21 * OTHER DEALINGS IN THE SOFTWARE. 22 */ 23 24 #ifndef DRM_MODESET_LOCK_H_ 25 #define DRM_MODESET_LOCK_H_ 26 27 #include <linux/types.h> /* stackdepot.h is not self-contained */ 28 #include <linux/stackdepot.h> 29 #include <linux/ww_mutex.h> 30 31 struct drm_modeset_lock; 32 33 /** 34 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx) 35 * @ww_ctx: base acquire ctx 36 * @contended: used internally for -EDEADLK handling 37 * @stack_depot: used internally for contention debugging 38 * @locked: list of held locks 39 * @trylock_only: trylock mode used in atomic contexts/panic notifiers 40 * @interruptible: whether interruptible locking should be used. 41 * 42 * Each thread competing for a set of locks must use one acquire 43 * ctx. And if any lock fxn returns -EDEADLK, it must backoff and 44 * retry. 45 */ 46 struct drm_modeset_acquire_ctx { 47 48 struct ww_acquire_ctx ww_ctx; 49 50 /* 51 * Contended lock: if a lock is contended you should only call 52 * drm_modeset_backoff() which drops locks and slow-locks the 53 * contended lock. 54 */ 55 struct drm_modeset_lock *contended; 56 57 /* 58 * Stack depot for debugging when a contended lock was not backed off 59 * from. 60 */ 61 depot_stack_handle_t stack_depot; 62 63 /* 64 * list of held locks (drm_modeset_lock) 65 */ 66 struct list_head locked; 67 68 /* 69 * Trylock mode, use only for panic handlers! 70 */ 71 bool trylock_only; 72 73 /* Perform interruptible waits on this context. */ 74 bool interruptible; 75 }; 76 77 /** 78 * struct drm_modeset_lock - used for locking modeset resources. 79 * @mutex: resource locking 80 * @head: used to hold its place on &drm_atomi_state.locked list when 81 * part of an atomic update 82 * 83 * Used for locking CRTCs and other modeset resources. 84 */ 85 struct drm_modeset_lock { 86 /* 87 * modeset lock 88 */ 89 struct ww_mutex mutex; 90 91 /* 92 * Resources that are locked as part of an atomic update are added 93 * to a list (so we know what to unlock at the end). 94 */ 95 struct list_head head; 96 }; 97 98 #define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0) 99 100 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, 101 uint32_t flags); 102 void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx); 103 void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx); 104 int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx); 105 106 void drm_modeset_lock_init(struct drm_modeset_lock *lock); 107 108 /** 109 * drm_modeset_lock_fini - cleanup lock 110 * @lock: lock to cleanup 111 */ 112 static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock) 113 { 114 WARN_ON(!list_empty(&lock->head)); 115 } 116 117 /** 118 * drm_modeset_is_locked - equivalent to mutex_is_locked() 119 * @lock: lock to check 120 */ 121 static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock) 122 { 123 return ww_mutex_is_locked(&lock->mutex); 124 } 125 126 /** 127 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held() 128 * @lock: lock to check 129 */ 130 static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock) 131 { 132 lockdep_assert_held(&lock->mutex.base); 133 } 134 135 int drm_modeset_lock(struct drm_modeset_lock *lock, 136 struct drm_modeset_acquire_ctx *ctx); 137 int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock); 138 void drm_modeset_unlock(struct drm_modeset_lock *lock); 139 140 struct drm_device; 141 struct drm_crtc; 142 struct drm_plane; 143 144 void drm_modeset_lock_all(struct drm_device *dev); 145 void drm_modeset_unlock_all(struct drm_device *dev); 146 void drm_warn_on_modeset_not_all_locked(struct drm_device *dev); 147 148 int drm_modeset_lock_all_ctx(struct drm_device *dev, 149 struct drm_modeset_acquire_ctx *ctx); 150 151 /** 152 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks 153 * @dev: drm device 154 * @ctx: local modeset acquire context, will be dereferenced 155 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init() 156 * @ret: local ret/err/etc variable to track error status 157 * 158 * Use these macros to simplify grabbing all modeset locks using a local 159 * context. This has the advantage of reducing boilerplate, but also properly 160 * checking return values where appropriate. 161 * 162 * Any code run between BEGIN and END will be holding the modeset locks. 163 * 164 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and 165 * forth between the labels on deadlock and error conditions. 166 * 167 * Drivers can acquire additional modeset locks. If any lock acquisition 168 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with 169 * the @ret parameter containing the return value of drm_modeset_lock(). 170 * 171 * Returns: 172 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN() 173 * is 0, so no error checking is necessary 174 */ 175 #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \ 176 if (!drm_drv_uses_atomic_modeset(dev)) \ 177 mutex_lock(&dev->mode_config.mutex); \ 178 drm_modeset_acquire_init(&ctx, flags); \ 179 modeset_lock_retry: \ 180 ret = drm_modeset_lock_all_ctx(dev, &ctx); \ 181 if (ret) \ 182 goto modeset_lock_fail; 183 184 /** 185 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks 186 * @dev: drm device 187 * @ctx: local modeset acquire context, will be dereferenced 188 * @ret: local ret/err/etc variable to track error status 189 * 190 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN 191 * if ret is -EDEADLK. 192 * 193 * It's important that you use the same ret variable for begin and end so 194 * deadlock conditions are properly handled. 195 * 196 * Returns: 197 * ret will be untouched unless it is -EDEADLK on entry. That means that if you 198 * successfully acquire the locks, ret will be whatever your code sets it to. If 199 * there is a deadlock or other failure with acquire or backoff, ret will be set 200 * to that failure. In both of these cases the code between BEGIN/END will not 201 * be run, so the failure will reflect the inability to grab the locks. 202 */ 203 #define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret) \ 204 modeset_lock_fail: \ 205 if (ret == -EDEADLK) { \ 206 ret = drm_modeset_backoff(&ctx); \ 207 if (!ret) \ 208 goto modeset_lock_retry; \ 209 } \ 210 drm_modeset_drop_locks(&ctx); \ 211 drm_modeset_acquire_fini(&ctx); \ 212 if (!drm_drv_uses_atomic_modeset(dev)) \ 213 mutex_unlock(&dev->mode_config.mutex); 214 215 #endif /* DRM_MODESET_LOCK_H_ */ 216