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reservation: update api and add some helpers
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Move the list of shared fences to a struct, and return it in
reservation_object_get_list().
Add reservation_object_get_excl to get the exclusive fence.

Add reservation_object_reserve_shared(), which reserves space
in the reservation_object for 1 more shared fence.

reservation_object_add_shared_fence() and
reservation_object_add_excl_fence() are used to assign a new
fence to a reservation_object pointer, to complete a reservation.

Changes since v1:
- Add reservation_object_get_excl, reorder code a bit.

Signed-off-by: Maarten Lankhorst <[email protected]>
Acked-by: Sumit Semwal <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@gregkh
Maarten Lankhorst authored and gregkh committed Jul 8, 2014
1 parent 9b495a5 commit 04a5faa
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Showing 4 changed files with 229 additions and 19 deletions.
1 change: 1 addition & 0 deletions Documentation/DocBook/device-drivers.tmpl
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,7 @@ X!Edrivers/base/interface.c
!Edrivers/dma-buf/seqno-fence.c
!Iinclude/linux/fence.h
!Iinclude/linux/seqno-fence.h
!Edrivers/dma-buf/reservation.c
!Iinclude/linux/reservation.h
!Edrivers/base/dma-coherent.c
!Edrivers/base/dma-mapping.c
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35 changes: 24 additions & 11 deletions drivers/dma-buf/dma-buf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -134,7 +134,10 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
{
struct dma_buf *dmabuf;
struct reservation_object *resv;
struct reservation_object_list *fobj;
struct fence *fence_excl;
unsigned long events;
unsigned shared_count;

dmabuf = file->private_data;
if (!dmabuf || !dmabuf->resv)
Expand All @@ -150,12 +153,18 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)

ww_mutex_lock(&resv->lock, NULL);

if (resv->fence_excl && (!(events & POLLOUT) ||
resv->fence_shared_count == 0)) {
fobj = resv->fence;
if (!fobj)
goto out;

shared_count = fobj->shared_count;
fence_excl = resv->fence_excl;

if (fence_excl && (!(events & POLLOUT) || shared_count == 0)) {
struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
unsigned long pevents = POLLIN;

if (resv->fence_shared_count == 0)
if (shared_count == 0)
pevents |= POLLOUT;

spin_lock_irq(&dmabuf->poll.lock);
Expand All @@ -167,19 +176,20 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
spin_unlock_irq(&dmabuf->poll.lock);

if (events & pevents) {
if (!fence_add_callback(resv->fence_excl,
&dcb->cb, dma_buf_poll_cb))
if (!fence_add_callback(fence_excl, &dcb->cb,
dma_buf_poll_cb)) {
events &= ~pevents;
else
} else {
/*
* No callback queued, wake up any additional
* waiters.
*/
dma_buf_poll_cb(NULL, &dcb->cb);
}
}
}

if ((events & POLLOUT) && resv->fence_shared_count > 0) {
if ((events & POLLOUT) && shared_count > 0) {
struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
int i;

Expand All @@ -194,15 +204,18 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
if (!(events & POLLOUT))
goto out;

for (i = 0; i < resv->fence_shared_count; ++i)
if (!fence_add_callback(resv->fence_shared[i],
&dcb->cb, dma_buf_poll_cb)) {
for (i = 0; i < shared_count; ++i) {
struct fence *fence = fobj->shared[i];

if (!fence_add_callback(fence, &dcb->cb,
dma_buf_poll_cb)) {
events &= ~POLLOUT;
break;
}
}

/* No callback queued, wake up any additional waiters. */
if (i == resv->fence_shared_count)
if (i == shared_count)
dma_buf_poll_cb(NULL, &dcb->cb);
}

Expand Down
156 changes: 155 additions & 1 deletion drivers/dma-buf/reservation.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (C) 2012-2013 Canonical Ltd
* Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
*
* Based on bo.c which bears the following copyright notice,
* but is dual licensed:
Expand Down Expand Up @@ -37,3 +37,157 @@

DEFINE_WW_CLASS(reservation_ww_class);
EXPORT_SYMBOL(reservation_ww_class);

/*
* Reserve space to add a shared fence to a reservation_object,
* must be called with obj->lock held.
*/
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;

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

fence_get(fence);

fobj->shared[i] = fence;

fence_put(old_fence);
return;
}
}

fence_get(fence);
fobj->shared[fobj->shared_count] = fence;
/*
* make the new fence visible before incrementing
* fobj->shared_count
*/
smp_wmb();
fobj->shared_count++;
}

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;

fence_get(fence);

if (!old) {
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) {
if (fence && old->shared[i]->context == fence->context) {
fence_put(old->shared[i]);
fobj->shared[i] = fence;
fence = NULL;
} else
fobj->shared[i] = old->shared[i];
}
if (fence)
fobj->shared[fobj->shared_count++] = fence;

done:
obj->fence = fobj;
kfree(old);
}

/*
* Add a fence to a shared slot, obj->lock must be held, and
* reservation_object_reserve_shared_fence 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);

void reservation_object_add_excl_fence(struct reservation_object *obj,
struct fence *fence)
{
struct fence *old_fence = obj->fence_excl;
struct reservation_object_list *old;
u32 i = 0;

old = reservation_object_get_list(obj);
if (old) {
i = old->shared_count;
old->shared_count = 0;
}

if (fence)
fence_get(fence);

obj->fence_excl = fence;

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

if (old_fence)
fence_put(old_fence);
}
EXPORT_SYMBOL(reservation_object_add_excl_fence);
56 changes: 49 additions & 7 deletions include/linux/reservation.h
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Original file line number Diff line number Diff line change
Expand Up @@ -45,36 +45,78 @@

extern struct ww_class reservation_ww_class;

struct reservation_object_list {
u32 shared_count, shared_max;
struct fence *shared[];
};

struct reservation_object {
struct ww_mutex lock;

struct fence *fence_excl;
struct fence **fence_shared;
u32 fence_shared_count, fence_shared_max;
struct reservation_object_list *fence;
struct reservation_object_list *staged;
};

#define reservation_object_assert_held(obj) \
lockdep_assert_held(&(obj)->lock.base)

static inline void
reservation_object_init(struct reservation_object *obj)
{
ww_mutex_init(&obj->lock, &reservation_ww_class);

obj->fence_shared_count = obj->fence_shared_max = 0;
obj->fence_shared = NULL;
obj->fence_excl = NULL;
obj->fence = NULL;
obj->staged = NULL;
}

static inline void
reservation_object_fini(struct reservation_object *obj)
{
int i;
struct reservation_object_list *fobj;

/*
* This object should be dead and all references must have
* been released to it.
*/
if (obj->fence_excl)
fence_put(obj->fence_excl);
for (i = 0; i < obj->fence_shared_count; ++i)
fence_put(obj->fence_shared[i]);
kfree(obj->fence_shared);

fobj = obj->fence;
if (fobj) {
for (i = 0; i < fobj->shared_count; ++i)
fence_put(fobj->shared[i]);

kfree(fobj);
}
kfree(obj->staged);

ww_mutex_destroy(&obj->lock);
}

static inline struct reservation_object_list *
reservation_object_get_list(struct reservation_object *obj)
{
reservation_object_assert_held(obj);

return obj->fence;
}

static inline struct fence *
reservation_object_get_excl(struct reservation_object *obj)
{
reservation_object_assert_held(obj);

return obj->fence_excl;
}

int reservation_object_reserve_shared(struct reservation_object *obj);
void reservation_object_add_shared_fence(struct reservation_object *obj,
struct fence *fence);

void reservation_object_add_excl_fence(struct reservation_object *obj,
struct fence *fence);

#endif /* _LINUX_RESERVATION_H */

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