/*
* Header file for reservations for dma-buf and ttm
*
* Copyright(C) 2011 Linaro Limited. All rights reserved.
* Copyright (C) 2012-2013 Canonical Ltd
* Copyright (C) 2012 Texas Instruments
*
* Authors:
* Rob Clark <robdclark@gmail.com>
* Maarten Lankhorst <maarten.lankhorst@canonical.com>
* Thomas Hellstrom <thellstrom-at-vmware-dot-com>
*
* Based on bo.c which bears the following copyright notice,
* but is dual licensed:
*
* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
* All Rights Reserved.
*
* 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, sub license, 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 (including the
* next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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 _LINUX_RESERVATION_H
#define _LINUX_RESERVATION_H
#include <linux/ww_mutex.h>
#include <linux/dma-fence.h>
#include <linux/slab.h>
#include <linux/seqlock.h>
#include <linux/rcupdate.h>
extern struct ww_class reservation_ww_class;
struct dma_resv_list;
/**
* struct dma_resv - a reservation object manages fences for a buffer
*
* There are multiple uses for this, with sometimes slightly different rules in
* how the fence slots are used.
*
* One use is to synchronize cross-driver access to a struct dma_buf, either for
* dynamic buffer management or just to handle implicit synchronization between
* different users of the buffer in userspace. See &dma_buf.resv for a more
* in-depth discussion.
*
* The other major use is to manage access and locking within a driver in a
* buffer based memory manager. struct ttm_buffer_object is the canonical
* example here, since this is where reservation objects originated from. But
* use in drivers is spreading and some drivers also manage struct
* drm_gem_object with the same scheme.
*/
struct dma_resv {
/**
* @lock:
*
* Update side lock. Don't use directly, instead use the wrapper
* functions like dma_resv_lock() and dma_resv_unlock().
*
* Drivers which use the reservation object to manage memory dynamically
* also use this lock to protect buffer object state like placement,
* allocation policies or throughout command submission.
*/
struct ww_mutex lock;
/**
* @seq:
*
* Sequence count for managing RCU read-side synchronization, allows
* read-only access to @fence_excl and @fence while ensuring we take a
* consistent snapshot.
*/
seqcount_ww_mutex_t seq;
/**
* @fence_excl:
*
* The exclusive fence, if there is one currently.
*
* To guarantee that no fences are lost, this new fence must signal
* only after the previous exclusive fence has signalled. If
* semantically only a new access is added without actually treating the
* previous one as a dependency the exclusive fences can be strung
* together using struct dma_fence_chain.
*
* Note that actual semantics of what an exclusive or shared fence mean
* is defined by the user, for reservation objects shared across drivers
* see &dma_buf.resv.
*/
struct dma_fence __rcu *fence_excl;
/**
* @fence:
*
* List of current shared fences.
*
* There are no ordering constraints of shared fences against the
* exclusive fence slot. If a waiter needs to wait for all access, it
* has to wait for both sets of fences to signal.
*
* A new fence is added by calling dma_resv_add_shared_fence(). Since
* this often needs to be done past the point of no return in command
* submission it cannot fail, and therefore sufficient slots need to be
* reserved by calling dma_resv_reserve_shared().
*
* Note that actual semantics of what an exclusive or shared fence mean
* is defined by the user, for reservation objects shared across drivers
* see &dma_buf.resv.
*/
struct dma_resv_list __rcu *fence;
};
/**
* struct dma_resv_iter - current position into the dma_resv fences
*
* Don't touch this directly in the driver, use the accessor function instead.
*
* IMPORTANT
*
* When using the lockless iterators like dma_resv_iter_next_unlocked() or
* dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted.
* Code which accumulates statistics or similar needs to check for this with
* dma_resv_iter_is_restarted().
*/
struct dma_resv_iter {
/** @obj: The dma_resv object we iterate over */
struct dma_resv *obj;
/** @all_fences: If all fences should be returned */
bool all_fences;
/** @fence: the currently handled fence */
struct dma_fence *fence;
/** @seq: sequence number to check for modifications */
unsigned int seq;
/** @index: index into the shared fences */
unsigned int index;
/** @fences: the shared fences; private, *MUST* not dereference */
struct dma_resv_list *fences;
/** @shared_count: number of shared fences */
unsigned int shared_count;
/** @is_restarted: true if this is the first returned fence */
bool is_restarted;
};
struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
/**
* dma_resv_iter_begin - initialize a dma_resv_iter object
* @cursor: The dma_resv_iter object to initialize
* @obj: The dma_resv object which we want to iterate over
* @all_fences: If all fences should be returned or just the exclusive one
*/
static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
struct dma_resv *obj,
bool all_fences)
{
cursor->obj = obj;
cursor->all_fences = all_fences;
cursor->fence = NULL;
}
/**
* dma_resv_iter_end - cleanup a dma_resv_iter object
* @cursor: the dma_resv_iter object which should be cleaned up
*
* Make sure that the reference to the fence in the cursor is properly
* dropped.
*/
static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
{
dma_fence_put(cursor->fence);
}
/**
* dma_resv_iter_is_exclusive - test if the current fence is the exclusive one
* @cursor: the cursor of the current position
*
* Returns true if the currently returned fence is the exclusive one.
*/
static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor)
{
return cursor->index == 0;
}
/**
* dma_resv_iter_is_restarted - test if this is the first fence after a restart
* @cursor: the cursor with the current position
*
* Return true if this is the first fence in an iteration after a restart.
*/
static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
{
return cursor->is_restarted;
}
/**
* dma_resv_for_each_fence_unlocked - unlocked fence iterator
* @cursor: a struct dma_resv_iter pointer
* @fence: the current fence
*
* Iterate over the fences in a struct dma_resv object without holding the
* &dma_resv.lock and using RCU instead. The cursor needs to be initialized
* with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside
* the iterator a reference to the dma_fence is held and the RCU lock dropped.
*
* Beware that the iterator can be restarted when the struct dma_resv for
* @cursor is modified. Code which accumulates statistics or similar needs to
* check for this with dma_resv_iter_is_restarted(). For this reason prefer the
* lock iterator dma_resv_for_each_fence() whenever possible.
*/
#define dma_resv_for_each_fence_unlocked(cursor, fence) \
for (fence = dma_resv_iter_first_unlocked(cursor); \
fence; fence = dma_resv_iter_next_unlocked(cursor))
/**
* dma_resv_for_each_fence - fence iterator
* @cursor: a struct dma_resv_iter pointer
* @obj: a dma_resv object pointer
* @all_fences: true if all fences should be returned
* @fence: the current fence
*
* Iterate over the fences in a struct dma_resv object while holding the
* &dma_resv.lock. @all_fences controls if the shared fences are returned as
* well. The cursor initialisation is part of the iterator and the fence stays
* valid as long as the lock is held and so no extra reference to the fence is
* taken.
*/
#define dma_resv_for_each_fence(cursor, obj, all_fences, fence) \
for (dma_resv_iter_begin(cursor, obj, all_fences), \
fence = dma_resv_iter_first(cursor); fence; \
fence = dma_resv_iter_next(cursor))
#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
#ifdef CONFIG_DEBUG_MUTEXES
void dma_resv_reset_shared_max(struct dma_resv *obj);
#else
static inline void dma_resv_reset_shared_max(struct dma_resv *obj) {}
#endif
/**
* dma_resv_lock - lock the reservation object
* @obj: the reservation object
* @ctx: the locking context
*
* Locks the reservation object for exclusive access and modification. Note,
* that the lock is only against other writers, readers will run concurrently
* with a writer under RCU. The seqlock is used to notify readers if they
* overlap with a writer.
*
* As the reservation object may be locked by multiple parties in an
* undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
* is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
* object may be locked by itself by passing NULL as @ctx.
*
* When a die situation is indicated by returning -EDEADLK all locks held by
* @ctx must be unlocked and then dma_resv_lock_slow() called on @obj.
*
* Unlocked by calling dma_resv_unlock().
*
* See also dma_resv_lock_interruptible() for the interruptible variant.
*/
static inline int dma_resv_lock(struct dma_resv *obj,
struct ww_acquire_ctx *ctx)
{
return ww_mutex_lock(&obj->lock, ctx);
}
/**
* dma_resv_lock_interruptible - lock the reservation object
* @obj: the reservation object
* @ctx: the locking context
*
* Locks the reservation object interruptible for exclusive access and
* modification. Note, that the lock is only against other writers, readers
* will run concurrently with a writer under RCU. The seqlock is used to
* notify readers if they overlap with a writer.
*
* As the reservation object may be locked by multiple parties in an
* undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
* is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
* object may be locked by itself by passing NULL as @ctx.
*
* When a die situation is indicated by returning -EDEADLK all locks held by
* @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on
* @obj.
*
* Unlocked by calling dma_resv_unlock().
*/
static inline int dma_resv_lock_interruptible(struct dma_resv *obj,
struct ww_acquire_ctx *ctx)
{
return ww_mutex_lock_interruptible(&obj->lock, ctx);
}
/**
* dma_resv_lock_slow - slowpath lock the reservation object
* @obj: the reservation object
* @ctx: the locking context
*
* Acquires the reservation object after a die case. This function
* will sleep until the lock becomes available. See dma_resv_lock() as
* well.
*
* See also dma_resv_lock_slow_interruptible() for the interruptible variant.
*/
static inline void dma_resv_lock_slow(struct dma_resv *obj,
struct ww_acquire_ctx *ctx)
{
ww_mutex_lock_slow(&obj->lock, ctx);
}
/**
* dma_resv_lock_slow_interruptible - slowpath lock the reservation
* object, interruptible
* @obj: the reservation object
* @ctx: the locking context
*
* Acquires the reservation object interruptible after a die case. This function
* will sleep until the lock becomes available. See
* dma_resv_lock_interruptible() as well.
*/
static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
struct ww_acquire_ctx *ctx)
{
return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
}
/**
* dma_resv_trylock - trylock the reservation object
* @obj: the reservation object
*
* Tries to lock the reservation object for exclusive access and modification.
* Note, that the lock is only against other writers, readers will run
* concurrently with a writer under RCU. The seqlock is used to notify readers
* if they overlap with a writer.
*
* Also note that since no context is provided, no deadlock protection is
* possible, which is also not needed for a trylock.
*
* Returns true if the lock was acquired, false otherwise.
*/
static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
{
return ww_mutex_trylock(&obj->lock, NULL);
}
/**
* dma_resv_is_locked - is the reservation object locked
* @obj: the reservation object
*
* Returns true if the mutex is locked, false if unlocked.
*/
static inline bool dma_resv_is_locked(struct dma_resv *obj)
{
return ww_mutex_is_locked(&obj->lock);
}
/**
* dma_resv_locking_ctx - returns the context used to lock the object
* @obj: the reservation object
*
* Returns the context used to lock a reservation object or NULL if no context
* was used or the object is not locked at all.
*
* WARNING: This interface is pretty horrible, but TTM needs it because it
* doesn't pass the struct ww_acquire_ctx around in some very long callchains.
* Everyone else just uses it to check whether they're holding a reservation or
* not.
*/
static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj)
{
return READ_ONCE(obj->lock.ctx);
}
/**
* dma_resv_unlock - unlock the reservation object
* @obj: the reservation object
*
* Unlocks the reservation object following exclusive access.
*/
static inline void dma_resv_unlock(struct dma_resv *obj)
{
dma_resv_reset_shared_max(obj);
ww_mutex_unlock(&obj->lock);
}
/**
* dma_resv_excl_fence - return the object's exclusive fence
* @obj: the reservation object
*
* Returns the exclusive fence (if any). Caller must either hold the objects
* through dma_resv_lock() or the RCU read side lock through rcu_read_lock(),
* or one of the variants of each
*
* RETURNS
* The exclusive fence or NULL
*/
static inline struct dma_fence *
dma_resv_excl_fence(struct dma_resv *obj)
{
return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj));
}
void dma_resv_init(struct dma_resv *obj);
void dma_resv_fini(struct dma_resv *obj);
int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences);
void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence);
void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
struct dma_fence *fence);
void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence);
int dma_resv_get_fences(struct dma_resv *obj, bool write,
unsigned int *num_fences, struct dma_fence ***fences);
int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
unsigned long timeout);
bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all);
void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq);
#endif /* _LINUX_RESERVATION_H */
