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 * @locked: list of held locks
38 * @trylock_only: trylock mode used in atomic contexts/panic notifiers
39 * @interruptible: whether interruptible locking should be used.
40 *
41 * Each thread competing for a set of locks must use one acquire
42 * ctx. And if any lock fxn returns -EDEADLK, it must backoff and
43 * retry.
44 */
45 struct drm_modeset_acquire_ctx {
46
47 struct ww_acquire_ctx ww_ctx;
48
49 /*
50 * Contended lock: if a lock is contended you should only call
51 * drm_modeset_backoff() which drops locks and slow-locks the
52 * contended lock.
53 */
54 struct drm_modeset_lock *contended;
55
56 /*
57 * Stack depot for debugging when a contended lock was not backed off
58 * from.
59 */
60 depot_stack_handle_t stack_depot;
61
62 /*
63 * list of held locks (drm_modeset_lock)
64 */
65 struct list_head locked;
66
67 /*
68 * Trylock mode, use only for panic handlers!
69 */
70 bool trylock_only;
71
72 /* Perform interruptible waits on this context. */
73 bool interruptible;
74 };
75
76 /**
77 * struct drm_modeset_lock - used for locking modeset resources.
78 * @mutex: resource locking
79 * @head: used to hold its place on &drm_atomi_state.locked list when
80 * part of an atomic update
81 *
82 * Used for locking CRTCs and other modeset resources.
83 */
84 struct drm_modeset_lock {
85 /*
86 * modeset lock
87 */
88 struct ww_mutex mutex;
89
90 /*
91 * Resources that are locked as part of an atomic update are added
92 * to a list (so we know what to unlock at the end).
93 */
94 struct list_head head;
95 };
96
97 #define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)
98
99 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
100 uint32_t flags);
101 void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
102 void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);
103 int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);
104
105 void drm_modeset_lock_init(struct drm_modeset_lock *lock);
106
107 /**
108 * drm_modeset_lock_fini - cleanup lock
109 * @lock: lock to cleanup
110 */
drm_modeset_lock_fini(struct drm_modeset_lock * lock)111 static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock)
112 {
113 WARN_ON(!list_empty(&lock->head));
114 }
115
116 /**
117 * drm_modeset_is_locked - equivalent to mutex_is_locked()
118 * @lock: lock to check
119 */
drm_modeset_is_locked(struct drm_modeset_lock * lock)120 static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
121 {
122 return ww_mutex_is_locked(&lock->mutex);
123 }
124
125 /**
126 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held()
127 * @lock: lock to check
128 */
drm_modeset_lock_assert_held(struct drm_modeset_lock * lock)129 static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock)
130 {
131 lockdep_assert_held(&lock->mutex.base);
132 }
133
134 int drm_modeset_lock(struct drm_modeset_lock *lock,
135 struct drm_modeset_acquire_ctx *ctx);
136 int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
137 void drm_modeset_unlock(struct drm_modeset_lock *lock);
138
139 struct drm_device;
140 struct drm_crtc;
141 struct drm_plane;
142
143 void drm_modeset_lock_all(struct drm_device *dev);
144 void drm_modeset_unlock_all(struct drm_device *dev);
145 void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);
146
147 int drm_modeset_lock_all_ctx(struct drm_device *dev,
148 struct drm_modeset_acquire_ctx *ctx);
149
150 /**
151 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
152 * @dev: drm device
153 * @ctx: local modeset acquire context, will be dereferenced
154 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
155 * @ret: local ret/err/etc variable to track error status
156 *
157 * Use these macros to simplify grabbing all modeset locks using a local
158 * context. This has the advantage of reducing boilerplate, but also properly
159 * checking return values where appropriate.
160 *
161 * Any code run between BEGIN and END will be holding the modeset locks.
162 *
163 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
164 * forth between the labels on deadlock and error conditions.
165 *
166 * Drivers can acquire additional modeset locks. If any lock acquisition
167 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
168 * the @ret parameter containing the return value of drm_modeset_lock().
169 *
170 * Returns:
171 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
172 * is 0, so no error checking is necessary
173 */
174 #define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret) \
175 if (!drm_drv_uses_atomic_modeset(dev)) \
176 mutex_lock(&dev->mode_config.mutex); \
177 drm_modeset_acquire_init(&ctx, flags); \
178 modeset_lock_retry: \
179 ret = drm_modeset_lock_all_ctx(dev, &ctx); \
180 if (ret) \
181 goto modeset_lock_fail;
182
183 /**
184 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
185 * @dev: drm device
186 * @ctx: local modeset acquire context, will be dereferenced
187 * @ret: local ret/err/etc variable to track error status
188 *
189 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
190 * if ret is -EDEADLK.
191 *
192 * It's important that you use the same ret variable for begin and end so
193 * deadlock conditions are properly handled.
194 *
195 * Returns:
196 * ret will be untouched unless it is -EDEADLK on entry. That means that if you
197 * successfully acquire the locks, ret will be whatever your code sets it to. If
198 * there is a deadlock or other failure with acquire or backoff, ret will be set
199 * to that failure. In both of these cases the code between BEGIN/END will not
200 * be run, so the failure will reflect the inability to grab the locks.
201 */
202 #define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret) \
203 modeset_lock_fail: \
204 if (ret == -EDEADLK) { \
205 ret = drm_modeset_backoff(&ctx); \
206 if (!ret) \
207 goto modeset_lock_retry; \
208 } \
209 drm_modeset_drop_locks(&ctx); \
210 drm_modeset_acquire_fini(&ctx); \
211 if (!drm_drv_uses_atomic_modeset(dev)) \
212 mutex_unlock(&dev->mode_config.mutex);
213
214 #endif /* DRM_MODESET_LOCK_H_ */
215