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 */
drm_modeset_lock_fini(struct drm_modeset_lock * lock)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 */
drm_modeset_is_locked(struct drm_modeset_lock * lock)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 /**
118 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held()
119 * @lock: lock to check
120 */
drm_modeset_lock_assert_held(struct drm_modeset_lock * lock)121 static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock)
122 {
123 lockdep_assert_held(&lock->mutex.base);
124 }
125
126 int drm_modeset_lock(struct drm_modeset_lock *lock,
127 struct drm_modeset_acquire_ctx *ctx);
128 int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
129 void drm_modeset_unlock(struct drm_modeset_lock *lock);
130
131 struct drm_device;
132 struct drm_crtc;
133 struct drm_plane;
134
135 void drm_modeset_lock_all(struct drm_device *dev);
136 void drm_modeset_unlock_all(struct drm_device *dev);
137 void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);
138
139 int drm_modeset_lock_all_ctx(struct drm_device *dev,
140 struct drm_modeset_acquire_ctx *ctx);
141
142 /**
143 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
144 * @dev: drm device
145 * @ctx: local modeset acquire context, will be dereferenced
146 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
147 * @ret: local ret/err/etc variable to track error status
148 *
149 * Use these macros to simplify grabbing all modeset locks using a local
150 * context. This has the advantage of reducing boilerplate, but also properly
151 * checking return values where appropriate.
152 *
153 * Any code run between BEGIN and END will be holding the modeset locks.
154 *
155 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
156 * forth between the labels on deadlock and error conditions.
157 *
158 * Drivers can acquire additional modeset locks. If any lock acquisition
159 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
160 * the @ret parameter containing the return value of drm_modeset_lock().
161 *
162 * Returns:
163 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
164 * is 0, so no error checking is necessary
165 */
166 #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \
167 if (!drm_drv_uses_atomic_modeset(dev)) \
168 mutex_lock(&dev->mode_config.mutex); \
169 drm_modeset_acquire_init(&ctx, flags); \
170 modeset_lock_retry: \
171 ret = drm_modeset_lock_all_ctx(dev, &ctx); \
172 if (ret) \
173 goto modeset_lock_fail;
174
175 /**
176 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
177 * @dev: drm device
178 * @ctx: local modeset acquire context, will be dereferenced
179 * @ret: local ret/err/etc variable to track error status
180 *
181 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
182 * if ret is -EDEADLK.
183 *
184 * It's important that you use the same ret variable for begin and end so
185 * deadlock conditions are properly handled.
186 *
187 * Returns:
188 * ret will be untouched unless it is -EDEADLK on entry. That means that if you
189 * successfully acquire the locks, ret will be whatever your code sets it to. If
190 * there is a deadlock or other failure with acquire or backoff, ret will be set
191 * to that failure. In both of these cases the code between BEGIN/END will not
192 * be run, so the failure will reflect the inability to grab the locks.
193 */
194 #define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret) \
195 modeset_lock_fail: \
196 if (ret == -EDEADLK) { \
197 ret = drm_modeset_backoff(&ctx); \
198 if (!ret) \
199 goto modeset_lock_retry; \
200 } \
201 drm_modeset_drop_locks(&ctx); \
202 drm_modeset_acquire_fini(&ctx); \
203 if (!drm_drv_uses_atomic_modeset(dev)) \
204 mutex_unlock(&dev->mode_config.mutex);
205
206 #endif /* DRM_MODESET_LOCK_H_ */
207
