[deliverable/linux.git] / drivers / dma-buf / reservation.c

/*
 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
 *
 * 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.
 *
 **************************************************************************/
/*
 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 */

#include <linux/reservation.h>
#include <linux/export.h>

/**
 * DOC: Reservation Object Overview
 *
 * The reservation object provides a mechanism to manage shared and
 * exclusive fences associated with a buffer.  A reservation object
 * can have attached one exclusive fence (normally associated with
 * write operations) or N shared fences (read operations).  The RCU
 * mechanism is used to protect read access to fences from locked
 * write-side updates.
 */

DEFINE_WW_CLASS(reservation_ww_class);
EXPORT_SYMBOL(reservation_ww_class);

struct lock_class_key reservation_seqcount_class;
EXPORT_SYMBOL(reservation_seqcount_class);

const char reservation_seqcount_string[] = "reservation_seqcount";
EXPORT_SYMBOL(reservation_seqcount_string);

/**
 * reservation_object_reserve_shared - Reserve space to add a shared
 * fence to a reservation_object.
 * @obj: reservation object
 *
 * Should be called before reservation_object_add_shared_fence().  Must
 * be called with obj->lock held.
 *
 * RETURNS
 * Zero for success, or -errno
 */
int reservation_object_reserve_shared(struct reservation_object *obj)
{
	struct reservation_object_list *fobj, *old;
	u32 max;

	old = reservation_object_get_list(obj);

	if (old && old->shared_max) {
		if (old->shared_count < old->shared_max) {
			/* perform an in-place update */
			kfree(obj->staged);
			obj->staged = NULL;
			return 0;
		} else
			max = old->shared_max * 2;
	} else
		max = 4;

	/*
	 * resize obj->staged or allocate if it doesn't exist,
	 * noop if already correct size
	 */
	fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
			GFP_KERNEL);
	if (!fobj)
		return -ENOMEM;

	obj->staged = fobj;
	fobj->shared_max = max;
	return 0;
}
EXPORT_SYMBOL(reservation_object_reserve_shared);

static void
reservation_object_add_shared_inplace(struct reservation_object *obj,
				      struct reservation_object_list *fobj,
				      struct fence *fence)
{
	u32 i;

	fence_get(fence);

	preempt_disable();
	write_seqcount_begin(&obj->seq);

	for (i = 0; i < fobj->shared_count; ++i) {
		struct fence *old_fence;

		old_fence = rcu_dereference_protected(fobj->shared[i],
						reservation_object_held(obj));

		if (old_fence->context == fence->context) {
			/* memory barrier is added by write_seqcount_begin */
			RCU_INIT_POINTER(fobj->shared[i], fence);
			write_seqcount_end(&obj->seq);
			preempt_enable();

			fence_put(old_fence);
			return;
		}
	}

	/*
	 * memory barrier is added by write_seqcount_begin,
	 * fobj->shared_count is protected by this lock too
	 */
	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
	fobj->shared_count++;

	write_seqcount_end(&obj->seq);
	preempt_enable();
}

static void
reservation_object_add_shared_replace(struct reservation_object *obj,
				      struct reservation_object_list *old,
				      struct reservation_object_list *fobj,
				      struct fence *fence)
{
	unsigned i;
	struct fence *old_fence = NULL;

	fence_get(fence);

	if (!old) {
		RCU_INIT_POINTER(fobj->shared[0], fence);
		fobj->shared_count = 1;
		goto done;
	}

	/*
	 * no need to bump fence refcounts, rcu_read access
	 * requires the use of kref_get_unless_zero, and the
	 * references from the old struct are carried over to
	 * the new.
	 */
	fobj->shared_count = old->shared_count;

	for (i = 0; i < old->shared_count; ++i) {
		struct fence *check;

		check = rcu_dereference_protected(old->shared[i],
						reservation_object_held(obj));

		if (!old_fence && check->context == fence->context) {
			old_fence = check;
			RCU_INIT_POINTER(fobj->shared[i], fence);
		} else
			RCU_INIT_POINTER(fobj->shared[i], check);
	}
	if (!old_fence) {
		RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
		fobj->shared_count++;
	}

done:
	preempt_disable();
	write_seqcount_begin(&obj->seq);
	/*
	 * RCU_INIT_POINTER can be used here,
	 * seqcount provides the necessary barriers
	 */
	RCU_INIT_POINTER(obj->fence, fobj);
	write_seqcount_end(&obj->seq);
	preempt_enable();

	if (old)
		kfree_rcu(old, rcu);

	if (old_fence)
		fence_put(old_fence);
}

/**
 * reservation_object_add_shared_fence - Add a fence to a shared slot
 * @obj: the reservation object
 * @fence: the shared fence to add
 *
 * Add a fence to a shared slot, obj->lock must be held, and
 * reservation_object_reserve_shared() has been called.
 */
void reservation_object_add_shared_fence(struct reservation_object *obj,
					 struct fence *fence)
{
	struct reservation_object_list *old, *fobj = obj->staged;

	old = reservation_object_get_list(obj);
	obj->staged = NULL;

	if (!fobj) {
		BUG_ON(old->shared_count >= old->shared_max);
		reservation_object_add_shared_inplace(obj, old, fence);
	} else
		reservation_object_add_shared_replace(obj, old, fobj, fence);
}
EXPORT_SYMBOL(reservation_object_add_shared_fence);

/**
 * reservation_object_add_excl_fence - Add an exclusive fence.
 * @obj: the reservation object
 * @fence: the shared fence to add
 *
 * Add a fence to the exclusive slot.  The obj->lock must be held.
 */
void reservation_object_add_excl_fence(struct reservation_object *obj,
				       struct fence *fence)
{
	struct fence *old_fence = reservation_object_get_excl(obj);
	struct reservation_object_list *old;
	u32 i = 0;

	old = reservation_object_get_list(obj);
	if (old)
		i = old->shared_count;

	if (fence)
		fence_get(fence);

	preempt_disable();
	write_seqcount_begin(&obj->seq);
	/* write_seqcount_begin provides the necessary memory barrier */
	RCU_INIT_POINTER(obj->fence_excl, fence);
	if (old)
		old->shared_count = 0;
	write_seqcount_end(&obj->seq);
	preempt_enable();

	/* inplace update, no shared fences */
	while (i--)
		fence_put(rcu_dereference_protected(old->shared[i],
						reservation_object_held(obj)));

	if (old_fence)
		fence_put(old_fence);
}
EXPORT_SYMBOL(reservation_object_add_excl_fence);

/**
 * reservation_object_get_fences_rcu - Get an object's shared and exclusive
 * fences without update side lock held
 * @obj: the reservation object
 * @pfence_excl: the returned exclusive fence (or NULL)
 * @pshared_count: the number of shared fences returned
 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 * the required size, and must be freed by caller)
 *
 * RETURNS
 * Zero or -errno
 */
int reservation_object_get_fences_rcu(struct reservation_object *obj,
				      struct fence **pfence_excl,
				      unsigned *pshared_count,
				      struct fence ***pshared)
{
	unsigned shared_count = 0;
	unsigned retry = 1;
	struct fence **shared = NULL, *fence_excl = NULL;
	int ret = 0;

	while (retry) {
		struct reservation_object_list *fobj;
		unsigned seq;

		seq = read_seqcount_begin(&obj->seq);

		rcu_read_lock();

		fobj = rcu_dereference(obj->fence);
		if (fobj) {
			struct fence **nshared;
			size_t sz = sizeof(*shared) * fobj->shared_max;

			nshared = krealloc(shared, sz,
					   GFP_NOWAIT | __GFP_NOWARN);
			if (!nshared) {
				rcu_read_unlock();
				nshared = krealloc(shared, sz, GFP_KERNEL);
				if (nshared) {
					shared = nshared;
					continue;
				}

				ret = -ENOMEM;
				shared_count = 0;
				break;
			}
			shared = nshared;
			memcpy(shared, fobj->shared, sz);
			shared_count = fobj->shared_count;
		} else
			shared_count = 0;
		fence_excl = rcu_dereference(obj->fence_excl);

		retry = read_seqcount_retry(&obj->seq, seq);
		if (retry)
			goto unlock;

		if (!fence_excl || fence_get_rcu(fence_excl)) {
			unsigned i;

			for (i = 0; i < shared_count; ++i) {
				if (fence_get_rcu(shared[i]))
					continue;

				/* uh oh, refcount failed, abort and retry */
				while (i--)
					fence_put(shared[i]);

				if (fence_excl) {
					fence_put(fence_excl);
					fence_excl = NULL;
				}

				retry = 1;
				break;
			}
		} else
			retry = 1;

unlock:
		rcu_read_unlock();
	}
	*pshared_count = shared_count;
	if (shared_count)
		*pshared = shared;
	else {
		*pshared = NULL;
		kfree(shared);
	}
	*pfence_excl = fence_excl;

	return ret;
}
EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);

/**
 * reservation_object_wait_timeout_rcu - Wait on reservation's objects
 * shared and/or exclusive fences.
 * @obj: the reservation object
 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 * @intr: if true, do interruptible wait
 * @timeout: timeout value in jiffies or zero to return immediately
 *
 * RETURNS
 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 * greater than zer on success.
 */
long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
					 bool wait_all, bool intr,
					 unsigned long timeout)
{
	struct fence *fence;
	unsigned seq, shared_count, i = 0;
	long ret = timeout;

	if (!timeout)
		return reservation_object_test_signaled_rcu(obj, wait_all);

retry:
	fence = NULL;
	shared_count = 0;
	seq = read_seqcount_begin(&obj->seq);
	rcu_read_lock();

	if (wait_all) {
		struct reservation_object_list *fobj =
						rcu_dereference(obj->fence);

		if (fobj)
			shared_count = fobj->shared_count;

		if (read_seqcount_retry(&obj->seq, seq))
			goto unlock_retry;

		for (i = 0; i < shared_count; ++i) {
			struct fence *lfence = rcu_dereference(fobj->shared[i]);

			if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
				continue;

			if (!fence_get_rcu(lfence))
				goto unlock_retry;

			if (fence_is_signaled(lfence)) {
				fence_put(lfence);
				continue;
			}

			fence = lfence;
			break;
		}
	}

	if (!shared_count) {
		struct fence *fence_excl = rcu_dereference(obj->fence_excl);

		if (read_seqcount_retry(&obj->seq, seq))
			goto unlock_retry;

		if (fence_excl &&
		    !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
			if (!fence_get_rcu(fence_excl))
				goto unlock_retry;

			if (fence_is_signaled(fence_excl))
				fence_put(fence_excl);
			else
				fence = fence_excl;
		}
	}

	rcu_read_unlock();
	if (fence) {
		ret = fence_wait_timeout(fence, intr, ret);
		fence_put(fence);
		if (ret > 0 && wait_all && (i + 1 < shared_count))
			goto retry;
	}
	return ret;

unlock_retry:
	rcu_read_unlock();
	goto retry;
}
EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);


static inline int
reservation_object_test_signaled_single(struct fence *passed_fence)
{
	struct fence *fence, *lfence = passed_fence;
	int ret = 1;

	if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
		fence = fence_get_rcu(lfence);
		if (!fence)
			return -1;

		ret = !!fence_is_signaled(fence);
		fence_put(fence);
	}
	return ret;
}

/**
 * reservation_object_test_signaled_rcu - Test if a reservation object's
 * fences have been signaled.
 * @obj: the reservation object
 * @test_all: if true, test all fences, otherwise only test the exclusive
 * fence
 *
 * RETURNS
 * true if all fences signaled, else false
 */
bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
					  bool test_all)
{
	unsigned seq, shared_count;
	int ret = true;

retry:
	shared_count = 0;
	seq = read_seqcount_begin(&obj->seq);
	rcu_read_lock();

	if (test_all) {
		unsigned i;

		struct reservation_object_list *fobj =
						rcu_dereference(obj->fence);

		if (fobj)
			shared_count = fobj->shared_count;

		if (read_seqcount_retry(&obj->seq, seq))
			goto unlock_retry;

		for (i = 0; i < shared_count; ++i) {
			struct fence *fence = rcu_dereference(fobj->shared[i]);

			ret = reservation_object_test_signaled_single(fence);
			if (ret < 0)
				goto unlock_retry;
			else if (!ret)
				break;
		}

		/*
		 * There could be a read_seqcount_retry here, but nothing cares
		 * about whether it's the old or newer fence pointers that are
		 * signaled. That race could still have happened after checking
		 * read_seqcount_retry. If you care, use ww_mutex_lock.
		 */
	}

	if (!shared_count) {
		struct fence *fence_excl = rcu_dereference(obj->fence_excl);

		if (read_seqcount_retry(&obj->seq, seq))
			goto unlock_retry;

		if (fence_excl) {
			ret = reservation_object_test_signaled_single(
								fence_excl);
			if (ret < 0)
				goto unlock_retry;
		}
	}

	rcu_read_unlock();
	return ret;

unlock_retry:
	rcu_read_unlock();
	goto retry;
}
EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
Commit	Line	Data
786d7257	1	/*
04a5faa8	2	* Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
786d7257 ML	3	*
	4	* Based on bo.c which bears the following copyright notice,
	5	* but is dual licensed:
	6	*
	7	* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
	8	* All Rights Reserved.
	9	*
	10	* Permission is hereby granted, free of charge, to any person obtaining a
	11	* copy of this software and associated documentation files (the
	12	* "Software"), to deal in the Software without restriction, including
	13	* without limitation the rights to use, copy, modify, merge, publish,
	14	* distribute, sub license, and/or sell copies of the Software, and to
	15	* permit persons to whom the Software is furnished to do so, subject to
	16	* the following conditions:
	17	*
	18	* The above copyright notice and this permission notice (including the
	19	* next paragraph) shall be included in all copies or substantial portions
	20	* of the Software.
	21	*
	22	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	23	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	24	* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
	25	* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
	26	* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
	27	* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
	28	* USE OR OTHER DEALINGS IN THE SOFTWARE.
	29	*
	30	**************************************************************************/
	31	/*
	32	* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
	33	*/
	34
	35	#include <linux/reservation.h>
	36	#include <linux/export.h>
	37
dad6c394 RC	38	/**
	39	* DOC: Reservation Object Overview
	40	*
	41	* The reservation object provides a mechanism to manage shared and
	42	* exclusive fences associated with a buffer. A reservation object
	43	* can have attached one exclusive fence (normally associated with
	44	* write operations) or N shared fences (read operations). The RCU
	45	* mechanism is used to protect read access to fences from locked
	46	* write-side updates.
	47	*/
	48
786d7257 ML	49	DEFINE_WW_CLASS(reservation_ww_class);
786d7257 ML	50	EXPORT_SYMBOL(reservation_ww_class);
04a5faa8	51
3c3b177a ML	52	struct lock_class_key reservation_seqcount_class;
	53	EXPORT_SYMBOL(reservation_seqcount_class);
	54
	55	const char reservation_seqcount_string[] = "reservation_seqcount";
	56	EXPORT_SYMBOL(reservation_seqcount_string);
dad6c394 RC	57
	58	/**
	59	* reservation_object_reserve_shared - Reserve space to add a shared
	60	* fence to a reservation_object.
	61	* @obj: reservation object
	62	*
	63	* Should be called before reservation_object_add_shared_fence(). Must
	64	* be called with obj->lock held.
	65	*
	66	* RETURNS
	67	* Zero for success, or -errno
04a5faa8 ML	68	*/
	69	int reservation_object_reserve_shared(struct reservation_object *obj)
	70	{
	71	struct reservation_object_list fobj, old;
	72	u32 max;
	73
	74	old = reservation_object_get_list(obj);
	75
	76	if (old && old->shared_max) {
	77	if (old->shared_count < old->shared_max) {
	78	/* perform an in-place update */
	79	kfree(obj->staged);
	80	obj->staged = NULL;
	81	return 0;
	82	} else
	83	max = old->shared_max * 2;
	84	} else
	85	max = 4;
	86
	87	/*
	88	* resize obj->staged or allocate if it doesn't exist,
	89	* noop if already correct size
	90	*/
	91	fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
	92	GFP_KERNEL);
	93	if (!fobj)
	94	return -ENOMEM;
	95
	96	obj->staged = fobj;
	97	fobj->shared_max = max;
	98	return 0;
	99	}
	100	EXPORT_SYMBOL(reservation_object_reserve_shared);
	101
	102	static void
	103	reservation_object_add_shared_inplace(struct reservation_object *obj,
	104	struct reservation_object_list *fobj,
	105	struct fence *fence)
	106	{
	107	u32 i;
	108
3c3b177a ML	109	fence_get(fence);
	110
	111	preempt_disable();
	112	write_seqcount_begin(&obj->seq);
	113
04a5faa8	114	for (i = 0; i < fobj->shared_count; ++i) {
3c3b177a	115	struct fence *old_fence;
04a5faa8	116
3c3b177a ML	117	old_fence = rcu_dereference_protected(fobj->shared[i],
3c3b177a ML	118	reservation_object_held(obj));
04a5faa8	119
3c3b177a ML	120	if (old_fence->context == fence->context) {
	121	/* memory barrier is added by write_seqcount_begin */
	122	RCU_INIT_POINTER(fobj->shared[i], fence);
	123	write_seqcount_end(&obj->seq);
	124	preempt_enable();
04a5faa8 ML	125
	126	fence_put(old_fence);
	127	return;
	128	}
	129	}
	130
04a5faa8	131	/*
3c3b177a ML	132	* memory barrier is added by write_seqcount_begin,
3c3b177a ML	133	* fobj->shared_count is protected by this lock too
04a5faa8	134	*/
3c3b177a	135	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
04a5faa8	136	fobj->shared_count++;
3c3b177a ML	137
	138	write_seqcount_end(&obj->seq);
	139	preempt_enable();
04a5faa8 ML	140	}
	141
	142	static void
	143	reservation_object_add_shared_replace(struct reservation_object *obj,
	144	struct reservation_object_list *old,
	145	struct reservation_object_list *fobj,
	146	struct fence *fence)
	147	{
	148	unsigned i;
3c3b177a	149	struct fence *old_fence = NULL;
04a5faa8 ML	150
	151	fence_get(fence);
	152
	153	if (!old) {
3c3b177a	154	RCU_INIT_POINTER(fobj->shared[0], fence);
04a5faa8 ML	155	fobj->shared_count = 1;
	156	goto done;
	157	}
	158
	159	/*
	160	* no need to bump fence refcounts, rcu_read access
	161	* requires the use of kref_get_unless_zero, and the
	162	* references from the old struct are carried over to
	163	* the new.
	164	*/
	165	fobj->shared_count = old->shared_count;
	166
	167	for (i = 0; i < old->shared_count; ++i) {
3c3b177a ML	168	struct fence *check;
	169
	170	check = rcu_dereference_protected(old->shared[i],
	171	reservation_object_held(obj));
	172
	173	if (!old_fence && check->context == fence->context) {
	174	old_fence = check;
	175	RCU_INIT_POINTER(fobj->shared[i], fence);
04a5faa8	176	} else
3c3b177a ML	177	RCU_INIT_POINTER(fobj->shared[i], check);
	178	}
	179	if (!old_fence) {
	180	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
	181	fobj->shared_count++;
04a5faa8	182	}
04a5faa8 ML	183
04a5faa8 ML	184	done:
3c3b177a ML	185	preempt_disable();
	186	write_seqcount_begin(&obj->seq);
	187	/*
	188	* RCU_INIT_POINTER can be used here,
	189	* seqcount provides the necessary barriers
	190	*/
	191	RCU_INIT_POINTER(obj->fence, fobj);
	192	write_seqcount_end(&obj->seq);
	193	preempt_enable();
	194
	195	if (old)
	196	kfree_rcu(old, rcu);
	197
	198	if (old_fence)
	199	fence_put(old_fence);
04a5faa8 ML	200	}
04a5faa8 ML	201
dad6c394 RC	202	/**
	203	* reservation_object_add_shared_fence - Add a fence to a shared slot
	204	* @obj: the reservation object
	205	* @fence: the shared fence to add
	206	*
04a5faa8	207	* Add a fence to a shared slot, obj->lock must be held, and
f5bef0b8	208	* reservation_object_reserve_shared() has been called.
04a5faa8 ML	209	*/
	210	void reservation_object_add_shared_fence(struct reservation_object *obj,
	211	struct fence *fence)
	212	{
	213	struct reservation_object_list old, fobj = obj->staged;
	214
	215	old = reservation_object_get_list(obj);
	216	obj->staged = NULL;
	217
	218	if (!fobj) {
3c3b177a	219	BUG_ON(old->shared_count >= old->shared_max);
04a5faa8 ML	220	reservation_object_add_shared_inplace(obj, old, fence);
	221	} else
	222	reservation_object_add_shared_replace(obj, old, fobj, fence);
	223	}
	224	EXPORT_SYMBOL(reservation_object_add_shared_fence);
	225
dad6c394 RC	226	/**
	227	* reservation_object_add_excl_fence - Add an exclusive fence.
	228	* @obj: the reservation object
	229	* @fence: the shared fence to add
	230	*
	231	* Add a fence to the exclusive slot. The obj->lock must be held.
	232	*/
04a5faa8 ML	233	void reservation_object_add_excl_fence(struct reservation_object *obj,
	234	struct fence *fence)
	235	{
3c3b177a	236	struct fence *old_fence = reservation_object_get_excl(obj);
04a5faa8 ML	237	struct reservation_object_list *old;
	238	u32 i = 0;
	239
	240	old = reservation_object_get_list(obj);
3c3b177a	241	if (old)
04a5faa8	242	i = old->shared_count;
04a5faa8 ML	243
	244	if (fence)
	245	fence_get(fence);
	246
3c3b177a ML	247	preempt_disable();
	248	write_seqcount_begin(&obj->seq);
	249	/* write_seqcount_begin provides the necessary memory barrier */
	250	RCU_INIT_POINTER(obj->fence_excl, fence);
	251	if (old)
	252	old->shared_count = 0;
	253	write_seqcount_end(&obj->seq);
	254	preempt_enable();
04a5faa8 ML	255
	256	/* inplace update, no shared fences */
	257	while (i--)
3c3b177a ML	258	fence_put(rcu_dereference_protected(old->shared[i],
3c3b177a ML	259	reservation_object_held(obj)));
04a5faa8 ML	260
	261	if (old_fence)
	262	fence_put(old_fence);
	263	}
	264	EXPORT_SYMBOL(reservation_object_add_excl_fence);
3c3b177a	265
dad6c394 RC	266	/**
	267	* reservation_object_get_fences_rcu - Get an object's shared and exclusive
	268	* fences without update side lock held
	269	* @obj: the reservation object
	270	* @pfence_excl: the returned exclusive fence (or NULL)
	271	* @pshared_count: the number of shared fences returned
	272	* @pshared: the array of shared fence ptrs returned (array is krealloc'd to
	273	* the required size, and must be freed by caller)
	274	*
	275	* RETURNS
	276	* Zero or -errno
	277	*/
3c3b177a ML	278	int reservation_object_get_fences_rcu(struct reservation_object *obj,
	279	struct fence **pfence_excl,
	280	unsigned *pshared_count,
	281	struct fence ***pshared)
	282	{
	283	unsigned shared_count = 0;
	284	unsigned retry = 1;
	285	struct fence *shared = NULL, fence_excl = NULL;
	286	int ret = 0;
	287
	288	while (retry) {
	289	struct reservation_object_list *fobj;
	290	unsigned seq;
	291
	292	seq = read_seqcount_begin(&obj->seq);
	293
	294	rcu_read_lock();
	295
	296	fobj = rcu_dereference(obj->fence);
	297	if (fobj) {
	298	struct fence **nshared;
	299	size_t sz = sizeof(shared) fobj->shared_max;
	300
	301	nshared = krealloc(shared, sz,
	302	GFP_NOWAIT \| __GFP_NOWARN);
	303	if (!nshared) {
	304	rcu_read_unlock();
	305	nshared = krealloc(shared, sz, GFP_KERNEL);
	306	if (nshared) {
	307	shared = nshared;
	308	continue;
	309	}
	310
	311	ret = -ENOMEM;
	312	shared_count = 0;
	313	break;
	314	}
	315	shared = nshared;
	316	memcpy(shared, fobj->shared, sz);
	317	shared_count = fobj->shared_count;
	318	} else
	319	shared_count = 0;
	320	fence_excl = rcu_dereference(obj->fence_excl);
	321
	322	retry = read_seqcount_retry(&obj->seq, seq);
	323	if (retry)
	324	goto unlock;
	325
	326	if (!fence_excl \|\| fence_get_rcu(fence_excl)) {
	327	unsigned i;
	328
	329	for (i = 0; i < shared_count; ++i) {
	330	if (fence_get_rcu(shared[i]))
	331	continue;
	332
	333	/* uh oh, refcount failed, abort and retry */
	334	while (i--)
	335	fence_put(shared[i]);
	336
	337	if (fence_excl) {
	338	fence_put(fence_excl);
	339	fence_excl = NULL;
	340	}
	341
342	retry = 1;
343	break;
344	}
345	} else
346	retry = 1;
347
348	unlock:
349	rcu_read_unlock();
350	}
351	*pshared_count = shared_count;
352	if (shared_count)
353	*pshared = shared;
354	else {
355	*pshared = NULL;
356	kfree(shared);
357	}
358	*pfence_excl = fence_excl;
359
360	return ret;
361	}
362	EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
363
dad6c394 RC	364	/**
	365	* reservation_object_wait_timeout_rcu - Wait on reservation's objects
	366	* shared and/or exclusive fences.
	367	* @obj: the reservation object
	368	* @wait_all: if true, wait on all fences, else wait on just exclusive fence
	369	* @intr: if true, do interruptible wait
	370	* @timeout: timeout value in jiffies or zero to return immediately
	371	*
	372	* RETURNS
	373	* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
	374	* greater than zer on success.
	375	*/
3c3b177a ML	376	long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
	377	bool wait_all, bool intr,
	378	unsigned long timeout)
	379	{
	380	struct fence *fence;
	381	unsigned seq, shared_count, i = 0;
	382	long ret = timeout;
	383
fb8b7d2b JZ	384	if (!timeout)
	385	return reservation_object_test_signaled_rcu(obj, wait_all);
	386
3c3b177a ML	387	retry:
	388	fence = NULL;
	389	shared_count = 0;
	390	seq = read_seqcount_begin(&obj->seq);
	391	rcu_read_lock();
	392
	393	if (wait_all) {
5136629d JT	394	struct reservation_object_list *fobj =
5136629d JT	395	rcu_dereference(obj->fence);
3c3b177a ML	396
	397	if (fobj)
	398	shared_count = fobj->shared_count;
	399
	400	if (read_seqcount_retry(&obj->seq, seq))
	401	goto unlock_retry;
	402
	403	for (i = 0; i < shared_count; ++i) {
	404	struct fence *lfence = rcu_dereference(fobj->shared[i]);
	405
	406	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
	407	continue;
	408
	409	if (!fence_get_rcu(lfence))
	410	goto unlock_retry;
	411
	412	if (fence_is_signaled(lfence)) {
	413	fence_put(lfence);
	414	continue;
	415	}
	416
	417	fence = lfence;
	418	break;
	419	}
	420	}
	421
	422	if (!shared_count) {
	423	struct fence *fence_excl = rcu_dereference(obj->fence_excl);
	424
	425	if (read_seqcount_retry(&obj->seq, seq))
	426	goto unlock_retry;
	427
	428	if (fence_excl &&
	429	!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
	430	if (!fence_get_rcu(fence_excl))
	431	goto unlock_retry;
	432
	433	if (fence_is_signaled(fence_excl))
	434	fence_put(fence_excl);
	435	else
	436	fence = fence_excl;
	437	}
	438	}
	439
	440	rcu_read_unlock();
	441	if (fence) {
	442	ret = fence_wait_timeout(fence, intr, ret);
	443	fence_put(fence);
	444	if (ret > 0 && wait_all && (i + 1 < shared_count))
	445	goto retry;
	446	}
	447	return ret;
	448
	449	unlock_retry:
	450	rcu_read_unlock();
	451	goto retry;
	452	}
	453	EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
	454
	455
	456	static inline int
	457	reservation_object_test_signaled_single(struct fence *passed_fence)
	458	{
	459	struct fence fence, lfence = passed_fence;
460	int ret = 1;
461
462	if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
3c3b177a ML	463	fence = fence_get_rcu(lfence);
	464	if (!fence)
	465	return -1;
	466
	467	ret = !!fence_is_signaled(fence);
	468	fence_put(fence);
	469	}
	470	return ret;
	471	}
	472
dad6c394 RC	473	/**
	474	* reservation_object_test_signaled_rcu - Test if a reservation object's
	475	* fences have been signaled.
	476	* @obj: the reservation object
	477	* @test_all: if true, test all fences, otherwise only test the exclusive
	478	* fence
	479	*
	480	* RETURNS
	481	* true if all fences signaled, else false
	482	*/
3c3b177a ML	483	bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
	484	bool test_all)
	485	{
	486	unsigned seq, shared_count;
	487	int ret = true;
	488
	489	retry:
	490	shared_count = 0;
	491	seq = read_seqcount_begin(&obj->seq);
	492	rcu_read_lock();
	493
	494	if (test_all) {
	495	unsigned i;
	496
5136629d JT	497	struct reservation_object_list *fobj =
5136629d JT	498	rcu_dereference(obj->fence);
3c3b177a ML	499
	500	if (fobj)
	501	shared_count = fobj->shared_count;
	502
	503	if (read_seqcount_retry(&obj->seq, seq))
	504	goto unlock_retry;
	505
	506	for (i = 0; i < shared_count; ++i) {
	507	struct fence *fence = rcu_dereference(fobj->shared[i]);
	508
	509	ret = reservation_object_test_signaled_single(fence);
	510	if (ret < 0)
	511	goto unlock_retry;
	512	else if (!ret)
	513	break;
	514	}
	515
	516	/*
	517	* There could be a read_seqcount_retry here, but nothing cares
	518	* about whether it's the old or newer fence pointers that are
	519	* signaled. That race could still have happened after checking
	520	* read_seqcount_retry. If you care, use ww_mutex_lock.
	521	*/
	522	}
	523
	524	if (!shared_count) {
	525	struct fence *fence_excl = rcu_dereference(obj->fence_excl);
	526
	527	if (read_seqcount_retry(&obj->seq, seq))
	528	goto unlock_retry;
	529
	530	if (fence_excl) {
5136629d JT	531	ret = reservation_object_test_signaled_single(
5136629d JT	532	fence_excl);
3c3b177a ML	533	if (ret < 0)
	534	goto unlock_retry;
	535	}
	536	}
	537
	538	rcu_read_unlock();
	539	return ret;
	540
	541	unlock_retry:
	542	rcu_read_unlock();
	543	goto retry;
	544	}
	545	EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);