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/*
* 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
* @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_ */
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