/*
* 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 dma_fence *fence)
{
u32 i;
dma_fence_get(fence);
preempt_disable();
write_seqcount_begin(&obj->seq);
for (i = 0; i < fobj->shared_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) {
/* memory barrier is added by write_seqcount_begin */
RCU_INIT_POINTER(fobj->shared[i], fence);
write_seqcount_end(&obj->seq);
preempt_enable();
dma_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 dma_fence *fence)
{
unsigned i;
struct dma_fence *old_fence = NULL;
dma_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 dma_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)
dma_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 dma_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 dma_fence *fence)
{
struct dma_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)
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)));
if (old_fence)
dma_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 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 seq;
unsigned int i;
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) {
struct dma_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;
break;
}
shared = nshared;
shared_count = fobj->shared_count;
for (i = 0; i < shared_count; ++i) {
shared[i] = rcu_dereference(fobj->shared[i]);
if (!dma_fence_get_rcu(shared[i]))
break;
}
}
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;
*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, i = 0;
long ret = timeout ? timeout : 1;
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;
for (i = 0; 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;
}
}
if (!shared_count) {
struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
if (fence_excl &&
!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
&fence_excl->flags)) {
if (!dma_fence_get_rcu(fence_excl))
goto unlock_retry;
if (dma_fence_is_signaled(fence_excl))
dma_fence_put(fence_excl);
else
fence = fence_excl;
}
}
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);
