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@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 */
drm_modeset_lock_fini(struct drm_modeset_lock * lock)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 */
drm_modeset_is_locked(struct drm_modeset_lock * lock)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 */
drm_modeset_lock_assert_held(struct drm_modeset_lock * lock)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