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/ww_mutex.h> 28 29 struct drm_modeset_lock; 30 31 /** 32 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx) 33 * @ww_ctx: base acquire ctx 34 * @contended: used internally for -EDEADLK handling 35 * @locked: list of held locks 36 * @trylock_only: trylock mode used in atomic contexts/panic notifiers 37 * @interruptible: whether interruptible locking should be used. 38 * 39 * Each thread competing for a set of locks must use one acquire 40 * ctx. And if any lock fxn returns -EDEADLK, it must backoff and 41 * retry. 42 */ 43 struct drm_modeset_acquire_ctx { 44 45 struct ww_acquire_ctx ww_ctx; 46 47 /* 48 * Contended lock: if a lock is contended you should only call 49 * drm_modeset_backoff() which drops locks and slow-locks the 50 * contended lock. 51 */ 52 struct drm_modeset_lock *contended; 53 54 /* 55 * list of held locks (drm_modeset_lock) 56 */ 57 struct list_head locked; 58 59 /* 60 * Trylock mode, use only for panic handlers! 61 */ 62 bool trylock_only; 63 64 /* Perform interruptible waits on this context. */ 65 bool interruptible; 66 }; 67 68 /** 69 * struct drm_modeset_lock - used for locking modeset resources. 70 * @mutex: resource locking 71 * @head: used to hold its place on &drm_atomi_state.locked list when 72 * part of an atomic update 73 * 74 * Used for locking CRTCs and other modeset resources. 75 */ 76 struct drm_modeset_lock { 77 /* 78 * modeset lock 79 */ 80 struct ww_mutex mutex; 81 82 /* 83 * Resources that are locked as part of an atomic update are added 84 * to a list (so we know what to unlock at the end). 85 */ 86 struct list_head head; 87 }; 88 89 #define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0) 90 91 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, 92 uint32_t flags); 93 void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx); 94 void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx); 95 int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx); 96 97 void drm_modeset_lock_init(struct drm_modeset_lock *lock); 98 99 /** 100 * drm_modeset_lock_fini - cleanup lock 101 * @lock: lock to cleanup 102 */ 103 static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock) 104 { 105 WARN_ON(!list_empty(&lock->head)); 106 } 107 108 /** 109 * drm_modeset_is_locked - equivalent to mutex_is_locked() 110 * @lock: lock to check 111 */ 112 static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock) 113 { 114 return ww_mutex_is_locked(&lock->mutex); 115 } 116 117 int drm_modeset_lock(struct drm_modeset_lock *lock, 118 struct drm_modeset_acquire_ctx *ctx); 119 int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock); 120 void drm_modeset_unlock(struct drm_modeset_lock *lock); 121 122 struct drm_device; 123 struct drm_crtc; 124 struct drm_plane; 125 126 void drm_modeset_lock_all(struct drm_device *dev); 127 void drm_modeset_unlock_all(struct drm_device *dev); 128 void drm_warn_on_modeset_not_all_locked(struct drm_device *dev); 129 130 int drm_modeset_lock_all_ctx(struct drm_device *dev, 131 struct drm_modeset_acquire_ctx *ctx); 132 133 /** 134 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks 135 * @dev: drm device 136 * @ctx: local modeset acquire context, will be dereferenced 137 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init() 138 * @ret: local ret/err/etc variable to track error status 139 * 140 * Use these macros to simplify grabbing all modeset locks using a local 141 * context. This has the advantage of reducing boilerplate, but also properly 142 * checking return values where appropriate. 143 * 144 * Any code run between BEGIN and END will be holding the modeset locks. 145 * 146 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and 147 * forth between the labels on deadlock and error conditions. 148 * 149 * Drivers can acquire additional modeset locks. If any lock acquisition 150 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with 151 * the @ret parameter containing the return value of drm_modeset_lock(). 152 * 153 * Returns: 154 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN() 155 * is 0, so no error checking is necessary 156 */ 157 #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \ 158 drm_modeset_acquire_init(&ctx, flags); \ 159 modeset_lock_retry: \ 160 ret = drm_modeset_lock_all_ctx(dev, &ctx); \ 161 if (ret) \ 162 goto modeset_lock_fail; 163 164 /** 165 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks 166 * @ctx: local modeset acquire context, will be dereferenced 167 * @ret: local ret/err/etc variable to track error status 168 * 169 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN 170 * if ret is -EDEADLK. 171 * 172 * It's important that you use the same ret variable for begin and end so 173 * deadlock conditions are properly handled. 174 * 175 * Returns: 176 * ret will be untouched unless it is -EDEADLK on entry. That means that if you 177 * successfully acquire the locks, ret will be whatever your code sets it to. If 178 * there is a deadlock or other failure with acquire or backoff, ret will be set 179 * to that failure. In both of these cases the code between BEGIN/END will not 180 * be run, so the failure will reflect the inability to grab the locks. 181 */ 182 #define DRM_MODESET_LOCK_ALL_END(ctx, ret) \ 183 modeset_lock_fail: \ 184 if (ret == -EDEADLK) { \ 185 ret = drm_modeset_backoff(&ctx); \ 186 if (!ret) \ 187 goto modeset_lock_retry; \ 188 } \ 189 drm_modeset_drop_locks(&ctx); \ 190 drm_modeset_acquire_fini(&ctx); 191 192 #endif /* DRM_MODESET_LOCK_H_ */ 193