[PATCH v2 8/9] reservation: update api and add some helpers

Maarten Lankhorst
2014-07-01T10:57:54Z

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.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>

Changes since v1:
- Add reservation_object_get_excl, reorder code a bit.
---
Documentation/DocBook/device-drivers.tmpl | 1
drivers/dma-buf/dma-buf.c | 35 ++++---
drivers/dma-buf/reservation.c | 156 +++++++++++++++++++++++++++++
include/linux/reservation.h | 56 +++++++++-
4 files changed, 229 insertions(+), 19 deletions(-)

diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl
index ed0ef00cd7bc..dd3f278faa8a 100644
--- a/Documentation/DocBook/device-drivers.tmpl
+++ b/Documentation/DocBook/device-drivers.tmpl
@@ -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
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 25e8c4165936..cb8379dfeed5 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -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)
@@ -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);
@@ -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;

@@ -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);
}

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index a73fbf3b8e56..e6166723a9ae 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -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:
@@ -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);
diff --git a/include/linux/reservation.h b/include/linux/reservation.h
index f3f57460a205..2affe67dea6e 100644
--- a/include/linux/reservation.h
+++ b/include/linux/reservation.h
@@ -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 */