[linux-block.git] / include / drm / drm_modeset_lock.h

/*
 * Copyright (C) 2014 Red Hat
 * Author: Rob Clark <robdclark@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef DRM_MODESET_LOCK_H_
#define DRM_MODESET_LOCK_H_

#include <linux/types.h> /* stackdepot.h is not self-contained */
#include <linux/stackdepot.h>
#include <linux/ww_mutex.h>

struct drm_modeset_lock;

/**
 * struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx)
 * @ww_ctx: base acquire ctx
 * @contended: used internally for -EDEADLK handling
 * @stack_depot: used internally for contention debugging
 * @locked: list of held locks
 * @trylock_only: trylock mode used in atomic contexts/panic notifiers
 * @interruptible: whether interruptible locking should be used.
 *
 * Each thread competing for a set of locks must use one acquire
 * ctx.  And if any lock fxn returns -EDEADLK, it must backoff and
 * retry.
 */
struct drm_modeset_acquire_ctx {

	struct ww_acquire_ctx ww_ctx;

	/*
	 * Contended lock: if a lock is contended you should only call
	 * drm_modeset_backoff() which drops locks and slow-locks the
	 * contended lock.
	 */
	struct drm_modeset_lock *contended;

	/*
	 * Stack depot for debugging when a contended lock was not backed off
	 * from.
	 */
	depot_stack_handle_t stack_depot;

	/*
	 * list of held locks (drm_modeset_lock)
	 */
	struct list_head locked;

	/*
	 * Trylock mode, use only for panic handlers!
	 */
	bool trylock_only;

	/* Perform interruptible waits on this context. */
	bool interruptible;
};

/**
 * struct drm_modeset_lock - used for locking modeset resources.
 * @mutex: resource locking
 * @head: used to hold its place on &drm_atomi_state.locked list when
 *    part of an atomic update
 *
 * Used for locking CRTCs and other modeset resources.
 */
struct drm_modeset_lock {
	/*
	 * modeset lock
	 */
	struct ww_mutex mutex;

	/*
	 * Resources that are locked as part of an atomic update are added
	 * to a list (so we know what to unlock at the end).
	 */
	struct list_head head;
};

#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)

void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
		uint32_t flags);
void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx);
void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx);
int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);

void drm_modeset_lock_init(struct drm_modeset_lock *lock);

/**
 * drm_modeset_lock_fini - cleanup lock
 * @lock: lock to cleanup
 */
static inline void drm_modeset_lock_fini(struct drm_modeset_lock *lock)
{
	WARN_ON(!list_empty(&lock->head));
}

/**
 * drm_modeset_is_locked - equivalent to mutex_is_locked()
 * @lock: lock to check
 */
static inline bool drm_modeset_is_locked(struct drm_modeset_lock *lock)
{
	return ww_mutex_is_locked(&lock->mutex);
}

/**
 * drm_modeset_lock_assert_held - equivalent to lockdep_assert_held()
 * @lock: lock to check
 */
static inline void drm_modeset_lock_assert_held(struct drm_modeset_lock *lock)
{
	lockdep_assert_held(&lock->mutex.base);
}

int drm_modeset_lock(struct drm_modeset_lock *lock,
		struct drm_modeset_acquire_ctx *ctx);
int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
void drm_modeset_unlock(struct drm_modeset_lock *lock);

struct drm_device;
struct drm_crtc;
struct drm_plane;

void drm_modeset_lock_all(struct drm_device *dev);
void drm_modeset_unlock_all(struct drm_device *dev);
void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);

int drm_modeset_lock_all_ctx(struct drm_device *dev,
			     struct drm_modeset_acquire_ctx *ctx);

/**
 * DRM_MODESET_LOCK_ALL_BEGIN - Helper to acquire modeset locks
 * @dev: drm device
 * @ctx: local modeset acquire context, will be dereferenced
 * @flags: DRM_MODESET_ACQUIRE_* flags to pass to drm_modeset_acquire_init()
 * @ret: local ret/err/etc variable to track error status
 *
 * Use these macros to simplify grabbing all modeset locks using a local
 * context. This has the advantage of reducing boilerplate, but also properly
 * checking return values where appropriate.
 *
 * Any code run between BEGIN and END will be holding the modeset locks.
 *
 * This must be paired with DRM_MODESET_LOCK_ALL_END(). We will jump back and
 * forth between the labels on deadlock and error conditions.
 *
 * Drivers can acquire additional modeset locks. If any lock acquisition
 * fails, the control flow needs to jump to DRM_MODESET_LOCK_ALL_END() with
 * the @ret parameter containing the return value of drm_modeset_lock().
 *
 * Returns:
 * The only possible value of ret immediately after DRM_MODESET_LOCK_ALL_BEGIN()
 * is 0, so no error checking is necessary
 */
#define DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, flags, ret)		\
	if (!drm_drv_uses_atomic_modeset(dev))				\
		mutex_lock(&dev->mode_config.mutex);			\
	drm_modeset_acquire_init(&ctx, flags);				\
modeset_lock_retry:							\
	ret = drm_modeset_lock_all_ctx(dev, &ctx);			\
	if (ret)							\
		goto modeset_lock_fail;

/**
 * DRM_MODESET_LOCK_ALL_END - Helper to release and cleanup modeset locks
 * @dev: drm device
 * @ctx: local modeset acquire context, will be dereferenced
 * @ret: local ret/err/etc variable to track error status
 *
 * The other side of DRM_MODESET_LOCK_ALL_BEGIN(). It will bounce back to BEGIN
 * if ret is -EDEADLK.
 *
 * It's important that you use the same ret variable for begin and end so
 * deadlock conditions are properly handled.
 *
 * Returns:
 * ret will be untouched unless it is -EDEADLK on entry. That means that if you
 * successfully acquire the locks, ret will be whatever your code sets it to. If
 * there is a deadlock or other failure with acquire or backoff, ret will be set
 * to that failure. In both of these cases the code between BEGIN/END will not
 * be run, so the failure will reflect the inability to grab the locks.
 */
#define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret)				\
modeset_lock_fail:							\
	if (ret == -EDEADLK) {						\
		ret = drm_modeset_backoff(&ctx);			\
		if (!ret)						\
			goto modeset_lock_retry;			\
	}								\
	drm_modeset_drop_locks(&ctx);					\
	drm_modeset_acquire_fini(&ctx);					\
	if (!drm_drv_uses_atomic_modeset(dev))				\
		mutex_unlock(&dev->mode_config.mutex);

#endif /* DRM_MODESET_LOCK_H_ */
Commit	Line	Data
51fd371b RC	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
cd06ab2f JN	27	#include <linux/types.h> /* stackdepot.h is not self-contained */
cd06ab2f JN	28	#include <linux/stackdepot.h>
51fd371b RC	29	#include <linux/ww_mutex.h>
	30
	31	struct drm_modeset_lock;
	32
	33	/**
f3a80881	34	* struct drm_modeset_acquire_ctx - locking context (see ww_acquire_ctx)
51fd371b RC	35	* @ww_ctx: base acquire ctx
51fd371b RC	36	* @contended: used internally for -EDEADLK handling
6f043b59	37	* @stack_depot: used internally for contention debugging
51fd371b	38	* @locked: list of held locks
b7a1aafd	39	* @trylock_only: trylock mode used in atomic contexts/panic notifiers
6f8bcc74	40	* @interruptible: whether interruptible locking should be used.
51fd371b RC	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
fe8660ac	50	/*
51fd371b RC	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
cd06ab2f JN	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
fe8660ac	63	/*
51fd371b RC	64	* list of held locks (drm_modeset_lock)
	65	*/
	66	struct list_head locked;
cb597bb3	67
fe8660ac	68	/*
cb597bb3 DV	69	* Trylock mode, use only for panic handlers!
	70	*/
	71	bool trylock_only;
6f8bcc74 ML	72
	73	/* Perform interruptible waits on this context. */
	74	bool interruptible;
51fd371b RC	75	};
	76
	77	/**
f3a80881	78	* struct drm_modeset_lock - used for locking modeset resources.
51fd371b	79	* @mutex: resource locking
1e55a53a	80	* @head: used to hold its place on &drm_atomi_state.locked list when
51fd371b RC	81	* part of an atomic update
	82	*
	83	* Used for locking CRTCs and other modeset resources.
	84	*/
	85	struct drm_modeset_lock {
fe8660ac	86	/*
51fd371b RC	87	* modeset lock
	88	*/
	89	struct ww_mutex mutex;
	90
fe8660ac	91	/*
51fd371b RC	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
6f8bcc74 ML	98	#define DRM_MODESET_ACQUIRE_INTERRUPTIBLE BIT(0)
6f8bcc74 ML	99
51fd371b RC	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);
6f8bcc74	104	int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx);
51fd371b	105
35cf0350	106	void drm_modeset_lock_init(struct drm_modeset_lock *lock);
51fd371b RC	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	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	return ww_mutex_is_locked(&lock->mutex);
	124	}
	125
4fb419b2 VS	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
51fd371b RC	135	int drm_modeset_lock(struct drm_modeset_lock *lock,
51fd371b RC	136	struct drm_modeset_acquire_ctx *ctx);
6f8bcc74	137	int __must_check drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock);
51fd371b RC	138	void drm_modeset_unlock(struct drm_modeset_lock *lock);
	139
	140	struct drm_device;
d059f652	141	struct drm_crtc;
4d02e2de	142	struct drm_plane;
a6a8bb84	143
294a0d95 SP	144	void drm_modeset_lock_all(struct drm_device *dev);
294a0d95 SP	145	void drm_modeset_unlock_all(struct drm_device *dev);
a6a8bb84 DV	146	void drm_warn_on_modeset_not_all_locked(struct drm_device *dev);
a6a8bb84 DV	147
06eaae46 TR	148	int drm_modeset_lock_all_ctx(struct drm_device *dev,
06eaae46 TR	149	struct drm_modeset_acquire_ctx *ctx);
51fd371b	150
b7ea04d2 SP	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) \
77ef3857 DV	176	if (!drm_drv_uses_atomic_modeset(dev)) \
77ef3857 DV	177	mutex_lock(&dev->mode_config.mutex); \
b7ea04d2 SP	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
77ef3857	186	* @dev: drm device
b7ea04d2 SP	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	*/
77ef3857	203	#define DRM_MODESET_LOCK_ALL_END(dev, ctx, ret) \
b7ea04d2 SP	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); \
77ef3857 DV	211	drm_modeset_acquire_fini(&ctx); \
	212	if (!drm_drv_uses_atomic_modeset(dev)) \
	213	mutex_unlock(&dev->mode_config.mutex);
b7ea04d2	214
51fd371b	215	#endif /* DRM_MODESET_LOCK_H_ */