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: &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 | |