include/drm/drm_modeset_lock.h

   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  */
 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  */
 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  */
 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_ */