1 /* $NetBSD: drm_modeset_lock.h,v 1.5 2021/12/18 23:45:46 riastradh Exp $ */ 2 3 /* 4 * Copyright (C) 2014 Red Hat 5 * Author: Rob Clark <robdclark (at) gmail.com> 6 * 7 * Permission is hereby granted, free of charge, to any person obtaining a 8 * copy of this software and associated documentation files (the "Software"), 9 * to deal in the Software without restriction, including without limitation 10 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 11 * and/or sell copies of the Software, and to permit persons to whom the 12 * Software is furnished to do so, subject to the following conditions: 13 * 14 * The above copyright notice and this permission notice shall be included in 15 * all copies or substantial portions of the Software. 16 * 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 20 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR 21 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 22 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 23 * OTHER DEALINGS IN THE SOFTWARE. 24 */ 25 26 #ifndef DRM_MODESET_LOCK_H_ 27 #define DRM_MODESET_LOCK_H_ 28 29 #include <linux/ww_mutex.h> 30 #include <asm/bug.h> 31 32 struct drm_modeset_lock; 33 34 /** 35 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx) 36 * @ww_ctx: base acquire ctx 37 * @contended: used internally for -EDEADLK handling 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 * list of held locks (drm_modeset_lock) 59 */ 60 struct list_head locked; 61 62 /* 63 * Trylock mode, use only for panic handlers! 64 */ 65 bool trylock_only; 66 67 /* Perform interruptible waits on this context. */ 68 bool interruptible; 69 }; 70 71 /** 72 * struct drm_modeset_lock - used for locking modeset resources. 73 * @mutex: resource locking 74 * @head: used to hold its place on &drm_atomi_state.locked list when 75 * part of an atomic update 76 * 77 * Used for locking CRTCs and other modeset resources. 78 */ 79 struct drm_modeset_lock { 80 /* 81 * modeset lock 82 */ 83 struct ww_mutex mutex; 84 85 /* 86 * Resources that are locked as part of an atomic update are added 87 * to a list (so we know what to unlock at the end). 88 */ 89 struct list_head head; 90 }; 91 92 #define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0) 93 94 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx, 95 uint32_t flags); 96 void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx); 97 void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx); 98 int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx); 99 100 void drm_modeset_lock_init(struct drm_modeset_lock *lock); 101 102 /** 103 * drm_modeset_lock_fini - cleanup lock 104 * @lock: lock to cleanup 105 */ 106 static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock) 107 { 108 WARN_ON(!list_empty(&lock->head)); 109 ww_mutex_destroy(&lock->mutex); 110 } 111 112 /** 113 * drm_modeset_is_locked - equivalent to mutex_is_locked() 114 * @lock: lock to check 115 */ 116 static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock) 117 { 118 return ww_mutex_is_locked(&lock->mutex); 119 } 120 121 /** 122 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held() 123 * @lock: lock to check 124 */ 125 static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock) 126 { 127 lockdep_assert_held(&lock->mutex.base); 128 } 129 130 int drm_modeset_lock(struct drm_modeset_lock *lock, 131 struct drm_modeset_acquire_ctx *ctx); 132 int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock); 133 void drm_modeset_unlock(struct drm_modeset_lock *lock); 134 135 struct drm_device; 136 struct drm_crtc; 137 struct drm_plane; 138 139 void drm_modeset_lock_all(struct drm_device *dev); 140 void drm_modeset_unlock_all(struct drm_device *dev); 141 void drm_warn_on_modeset_not_all_locked(struct drm_device *dev); 142 143 int drm_modeset_lock_all_ctx(struct drm_device *dev, 144 struct drm_modeset_acquire_ctx *ctx); 145 146 /** 147 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks 148 * @dev: drm device 149 * @ctx: local modeset acquire context, will be dereferenced 150 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init() 151 * @ret: local ret/err/etc variable to track error status 152 * 153 * Use these macros to simplify grabbing all modeset locks using a local 154 * context. This has the advantage of reducing boilerplate, but also properly 155 * checking return values where appropriate. 156 * 157 * Any code run between BEGIN and END will be holding the modeset locks. 158 * 159 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and 160 * forth between the labels on deadlock and error conditions. 161 * 162 * Drivers can acquire additional modeset locks. If any lock acquisition 163 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with 164 * the @ret parameter containing the return value of drm_modeset_lock(). 165 * 166 * Returns: 167 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN() 168 * is 0, so no error checking is necessary 169 */ 170 #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \ 171 drm_modeset_acquire_init(&ctx, flags); \ 172 modeset_lock_retry: \ 173 ret = drm_modeset_lock_all_ctx(dev, &ctx); \ 174 if (ret) \ 175 goto modeset_lock_fail; 176 177 /** 178 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks 179 * @ctx: local modeset acquire context, will be dereferenced 180 * @ret: local ret/err/etc variable to track error status 181 * 182 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN 183 * if ret is -EDEADLK. 184 * 185 * It's important that you use the same ret variable for begin and end so 186 * deadlock conditions are properly handled. 187 * 188 * Returns: 189 * ret will be untouched unless it is -EDEADLK on entry. That means that if you 190 * successfully acquire the locks, ret will be whatever your code sets it to. If 191 * there is a deadlock or other failure with acquire or backoff, ret will be set 192 * to that failure. In both of these cases the code between BEGIN/END will not 193 * be run, so the failure will reflect the inability to grab the locks. 194 */ 195 #define DRM_MODESET_LOCK_ALL_END(ctx, ret) \ 196 modeset_lock_fail: \ 197 if (ret == -EDEADLK) { \ 198 ret = drm_modeset_backoff(&ctx); \ 199 if (!ret) \ 200 goto modeset_lock_retry; \ 201 } \ 202 drm_modeset_drop_locks(&ctx); \ 203 drm_modeset_acquire_fini(&ctx); 204 205 #endif /* DRM_MODESET_LOCK_H_ */ 206
Indexes created Sat Sep 20 22:09:52 GMT 2025