Line data    Source code

       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          34 :         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           0 :         return ww_mutex_is_locked(&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_ */