/*
* 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_WD_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 shared fences to
* a reservation_object.
* @obj: reservation object
* @num_fences: number of fences we want to add
*
* 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,
unsigned int num_fences)
{
struct reservation_object_list *old, *new;
unsigned int i, j, k, max;
reservation_object_assert_held(obj);
old = reservation_object_get_list(obj);
if (old && old->shared_max) {
if ((old->shared_count + num_fences) <= old->shared_max)
return 0;
else
max = max(old->shared_count + num_fences,
old->shared_max * 2);
} else {
max = 4;
}
new = kmalloc(offsetof(typeof(*new), shared[max]), GFP_KERNEL);
if (!new)
return -ENOMEM;
/*
* 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.
*/
for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
struct dma_fence *fence;
fence = rcu_dereference_protected(old->shared[i],
reservation_object_held(obj));
if (dma_fence_is_signaled(fence))
RCU_INIT_POINTER(new->shared[--k], fence);
else
RCU_INIT_POINTER(new->shared[j++], fence);
}
new->shared_count = j;
new->shared_max = max;
preempt_disable();
write_seqcount_begin(&obj->seq);
/*
* RCU_INIT_POINTER can be used here,
* seqcount provides the necessary barriers
*/
RCU_INIT_POINTER(obj->fence, new);
write_seqcount_end(&obj->seq);
preempt_enable();
if (!old)
return 0;
/* Drop the references to the signaled fences */
for (i = k; i < new->shared_max; ++i) {
struct dma_fence *fence;
fence = rcu_dereference_protected(new->shared[i],
reservation_object_held(obj));
dma_fence_put(fence);
}
kfree_rcu(old, rcu);
return 0;
}
EXPORT_SYMBOL(reservation_object_reserve_shared);
/**
* 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 dma_fence *fence)
{
struct reservation_object_list *fobj;
unsigned int i, count;
dma_fence_get(fence);
reservation_object_assert_held(obj);
fobj = reservation_object_get_list(obj);
count = fobj->shared_count;
preempt_disable();
write_seqcount_begin(&obj->seq);
for (i = 0; i < count; ++i) {
struct dma_fence *old_fence;
old_fence = rcu_dereference_protected(fobj->shared[i],
reservation_object_held(obj));
if (old_fence->context == fence->context ||
dma_fence_is_signaled(old_fence)) {
dma_fence_put(old_fence);
goto replace;
}
}
BUG_ON(fobj->shared_count >= fobj->shared_max);
count++;
replace:
RCU_INIT_POINTER(fobj->shared[i], fence);
/* pointer update must be visible before we extend the shared_count */
smp_store_mb(fobj->shared_count, count);
write_seqcount_end(&obj->seq);
preempt_enable();
}
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 dma_fence *fence)
{
struct dma_fence *old_fence = reservation_object_get_excl(obj);
struct reservation_object_list *old;
u32 i = 0;
reservation_object_assert_held(obj);
old = reservation_object_get_list(obj);
if (old)
i = old->shared_count;
if (fence)
dma_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--)
dma_fence_put(rcu_dereference_protected(old->shared[i],
reservation_object_held(obj)));
dma_fence_put(old_fence);
}
EXPORT_SYMBOL(reservation_object_add_excl_fence);
/**
* reservation_object_copy_fences - Copy all fences from src to dst.
* @dst: the destination reservation object
* @src: the source reservation object
*
* Copy all fences from src to dst. dst-lock must be held.
*/
int reservation_object_copy_fences(struct reservation_object *dst,
struct reservation_object *src)
{
struct reservation_object_list *src_list, *dst_list;
struct dma_fence *old, *new;
size_t size;
unsigned i;
reservation_object_assert_held(dst);
rcu_read_lock();
src_list = rcu_dereference(src->fence);
retry:
if (src_list) {
unsigned shared_count = src_list->shared_count;
size = offsetof(typeof(*src_list), shared[shared_count]);
rcu_read_unlock();
dst_list = kmalloc(size, GFP_KERNEL);
if (!dst_list)
return -ENOMEM;
rcu_read_lock();
src_list = rcu_dereference(src->fence);
if (!src_list || src_list->shared_count > shared_count) {
kfree(dst_list);
goto retry;
}
dst_list->shared_count = 0;
dst_list->shared_max = shared_count;
for (i = 0; i < src_list->shared_count; ++i) {
struct dma_fence *fence;
fence = rcu_dereference(src_list->shared[i]);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
&fence->flags))
continue;
if (!dma_fence_get_rcu(fence)) {
kfree(dst_list);
src_list = rcu_dereference(src->fence);
goto retry;
}
if (dma_fence_is_signaled(fence)) {
dma_fence_put(fence);
continue;
}
rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
}
} else {
dst_list = NULL;
}
new = dma_fence_get_rcu_safe(&src->fence_excl);
rcu_read_unlock();
src_list = reservation_object_get_list(dst);
old = reservation_object_get_excl(dst);
preempt_disable();
write_seqcount_begin(&dst->seq);
/* write_seqcount_begin provides the necessary memory barrier */
RCU_INIT_POINTER(dst->fence_excl, new);
RCU_INIT_POINTER(dst->fence, dst_list);
write_seqcount_end(&dst->seq);
preempt_enable();
if (src_list)
kfree_rcu(src_list, rcu);
dma_fence_put(old);
return 0;
}
EXPORT_SYMBOL(reservation_object_copy_fences);
/**
* 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)
*
* Retrieve all fences from the reservation object. If the pointer for the
* exclusive fence is not specified the fence is put into the array of the
* shared fences as well. Returns either zero or -ENOMEM.
*/
int reservation_object_get_fences_rcu(struct reservation_object *obj,
struct dma_fence **pfence_excl,
unsigned *pshared_count,
struct dma_fence ***pshared)
{
struct dma_fence **shared = NULL;
struct dma_fence *fence_excl;
unsigned int shared_count;
int ret = 1;
do {
struct reservation_object_list *fobj;
unsigned int i, seq;
size_t sz = 0;
shared_count = i = 0;
rcu_read_lock();
seq = read_seqcount_begin(&obj->seq);
fence_excl = rcu_dereference(obj->fence_excl);
if (fence_excl && !dma_fence_get_rcu(fence_excl))
goto unlock;
fobj = rcu_dereference(obj->fence);
if (fobj)
sz += sizeof(*shared) * fobj->shared_max;
if (!pfence_excl && fence_excl)
sz += sizeof(*shared);
if (sz) {
struct dma_fence **nshared;
nshared = krealloc(shared, sz,
GFP_NOWAIT | __GFP_NOWARN);
if (!nshared) {
rcu_read_unlock();
dma_fence_put(fence_excl);
fence_excl = NULL;
nshared = krealloc(shared, sz, GFP_KERNEL);
if (nshared) {
shared = nshared;
continue;
}
ret = -ENOMEM;
break;
}
shared = nshared;
shared_count = fobj ? fobj->shared_count : 0;
for (i = 0; i < shared_count; ++i) {
shared[i] = rcu_dereference(fobj->shared[i]);
if (!dma_fence_get_rcu(shared[i]))
break;
}
if (!pfence_excl && fence_excl) {
shared[i] = fence_excl;
fence_excl = NULL;
++i;
++shared_count;
}
}
if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
while (i--)
dma_fence_put(shared[i]);
dma_fence_put(fence_excl);
goto unlock;
}
ret = 0;
unlock:
rcu_read_unlock();
} while (ret);
if (!shared_count) {
kfree(shared);
shared = NULL;
}
*pshared_count = shared_count;
*pshared = shared;
if (pfence_excl)
*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 dma_fence *fence;
unsigned seq, shared_count;
long ret = timeout ? timeout : 1;
int i;
retry:
shared_count = 0;
seq = read_seqcount_begin(&obj->seq);
rcu_read_lock();
i = -1;
fence = rcu_dereference(obj->fence_excl);
if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
if (!dma_fence_get_rcu(fence))
goto unlock_retry;
if (dma_fence_is_signaled(fence)) {
dma_fence_put(fence);
fence = NULL;
}
} else {
fence = NULL;
}
if (wait_all) {
struct reservation_object_list *fobj =
rcu_dereference(obj->fence);
if (fobj)
shared_count = fobj->shared_count;
for (i = 0; !fence && i < shared_count; ++i) {
struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
&lfence->flags))
continue;
if (!dma_fence_get_rcu(lfence))
goto unlock_retry;
if (dma_fence_is_signaled(lfence)) {
dma_fence_put(lfence);
continue;
}
fence = lfence;
break;
}
}
rcu_read_unlock();
if (fence) {
if (read_seqcount_retry(&obj->seq, seq)) {
dma_fence_put(fence);
goto retry;
}
ret = dma_fence_wait_timeout(fence, intr, ret);
dma_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 dma_fence *passed_fence)
{
struct dma_fence *fence, *lfence = passed_fence;
int ret = 1;
if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
fence = dma_fence_get_rcu(lfence);
if (!fence)
return -1;
ret = !!dma_fence_is_signaled(fence);
dma_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;
rcu_read_lock();
retry:
ret = true;
shared_count = 0;
seq = read_seqcount_begin(&obj->seq);
if (test_all) {
unsigned i;
struct reservation_object_list *fobj =
rcu_dereference(obj->fence);
if (fobj)
shared_count = fobj->shared_count;
for (i = 0; i < shared_count; ++i) {
struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
ret = reservation_object_test_signaled_single(fence);
if (ret < 0)
goto retry;
else if (!ret)
break;
}
if (read_seqcount_retry(&obj->seq, seq))
goto retry;
}
if (!shared_count) {
struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
if (fence_excl) {
ret = reservation_object_test_signaled_single(
fence_excl);
if (ret < 0)
goto retry;
if (read_seqcount_retry(&obj->seq, seq))
goto retry;
}
}
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
