[PATCH v9 12/15] vb2: add out-fence support to QBUF

From: Ezequiel Garcia
Date: Fri May 04 2018 - 16:08:36 EST

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>

If V4L2_BUF_FLAG_OUT_FENCE flag is present on the QBUF call we create
an out_fence and send its fd to userspace in the fence_fd field as a
return arg for the QBUF call.

The fence is signaled on buffer_done(), when the job on the buffer is
finished.

v11: - Return fence_fd to userpace only in the QBUF ioctl.
- Rework implementation to avoid storing the sync_file
as state, which is not really needed.

v10: - use -EIO for fence error (Hans Verkuil)
- add comment around fence context creation (Hans Verkuil)

v9: - remove in-fences changes from this patch (Alex Courbot)
- improve fence context creation (Hans Verkuil)
- clean up out fences if vb2_core_qbuf() fails (Hans Verkuil)

v8: - return 0 as fence_fd if OUT_FENCE flag not used (Mauro)
- fix crash when checking not using fences in vb2_buffer_done()

v7: - merge patch that add the infrastructure to out-fences into
this one (Alex Courbot)
- Do not install the fd if there is no fence. (Alex Courbot)
- do not report error on requeueing, just WARN_ON_ONCE() (Hans)

v6: - get rid of the V4L2_EVENT_OUT_FENCE event. We always keep the
ordering in vb2 for queueing in the driver, so the event is not
necessary anymore and the out_fence_fd is sent back to userspace
on QBUF call return arg
- do not allow requeueing with out-fences, instead mark the buffer
with an error and wake up to userspace.
- send the out_fence_fd back to userspace on the fence_fd field

v5: - delay fd_install to DQ_EVENT (Hans)
- if queue is fully ordered send OUT_FENCE event right away
(Brian)
- rename 'q->ordered' to 'q->ordered_in_driver'
- merge change to implement OUT_FENCE event here

v4: - return the out_fence_fd in the BUF_QUEUED event(Hans)

v3: - add WARN_ON_ONCE(q->ordered) on requeueing (Hans)
- set the OUT_FENCE flag if there is a fence pending (Hans)
- call fd_install() after vb2_core_qbuf() (Hans)
- clean up fence if vb2_core_qbuf() fails (Hans)
- add list to store sync_file and fence for the next queued buffer

v2: check if the queue is ordered.

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
---
drivers/media/common/videobuf2/videobuf2-core.c | 95 +++++++++++++++++++++++--
drivers/media/common/videobuf2/videobuf2-v4l2.c | 22 +++++-
drivers/media/dvb-core/dvb_vb2.c | 2 +-
include/media/videobuf2-core.h | 16 ++++-
4 files changed, 127 insertions(+), 8 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 996b99497a98..0f7306a04db7 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
+#include <linux/sync_file.h>

#include <media/videobuf2-core.h>
#include <media/v4l2-mc.h>
@@ -357,6 +358,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
vb->planes[plane].length = plane_sizes[plane];
vb->planes[plane].min_length = plane_sizes[plane];
}
+ vb->out_fence_fd = -1;
q->bufs[vb->index] = vb;

/* Allocate video buffer memory for the MMAP type */
@@ -948,10 +950,22 @@ static void vb2_process_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state
case VB2_BUF_STATE_QUEUED:
return;
case VB2_BUF_STATE_REQUEUEING:
+ /* Requeuing with explicit synchronization, spit warning */
+ WARN_ON_ONCE(vb->out_fence);
+
if (q->start_streaming_called)
__enqueue_in_driver(vb);
return;
default:
+ if (vb->out_fence) {
+ if (state == VB2_BUF_STATE_ERROR)
+ dma_fence_set_error(vb->out_fence, -EIO);
+ dma_fence_signal(vb->out_fence);
+ dma_fence_put(vb->out_fence);
+ vb->out_fence = NULL;
+ vb->out_fence_fd = -1;
+ }
+
/* Inform any processes that may be waiting for buffers */
wake_up(&q->done_wq);
break;
@@ -1367,6 +1381,68 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
}
EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);

+static inline const char *vb2_fence_get_driver_name(struct dma_fence *fence)
+{
+ return "vb2_fence";
+}
+
+static inline const char *vb2_fence_get_timeline_name(struct dma_fence *fence)
+{
+ return "vb2_fence_timeline";
+}
+
+static inline bool vb2_fence_enable_signaling(struct dma_fence *fence)
+{
+ return true;
+}
+
+static const struct dma_fence_ops vb2_fence_ops = {
+ .get_driver_name = vb2_fence_get_driver_name,
+ .get_timeline_name = vb2_fence_get_timeline_name,
+ .enable_signaling = vb2_fence_enable_signaling,
+ .wait = dma_fence_default_wait,
+};
+
+static int vb2_setup_out_fence(struct vb2_queue *q, struct vb2_buffer *vb)
+{
+ struct sync_file *sync_file;
+ int ret;
+
+ vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
+
+ /*
+ * The same context can be used only if the queue is ordered,
+ * so if the queue is ordered create one when the queueing start,
+ * otherwise create one for every buffer
+ */
+ if (q->unordered || !q->queueing_started)
+ q->out_fence_context = dma_fence_context_alloc(1);
+
+ vb->out_fence = kzalloc(sizeof(*vb->out_fence), GFP_KERNEL);
+ if (!vb->out_fence) {
+ ret = -ENOMEM;
+ goto err_put_fd;
+ }
+ dma_fence_init(vb->out_fence, &vb2_fence_ops, &q->out_fence_lock,
+ q->out_fence_context, 1);
+
+ sync_file = sync_file_create(vb->out_fence);
+ if (!sync_file) {
+ ret = -ENOMEM;
+ goto err_free_fence;
+ }
+ fd_install(vb->out_fence_fd, sync_file->file);
+ return 0;
+
+err_free_fence:
+ dma_fence_put(vb->out_fence);
+ vb->out_fence = NULL;
+err_put_fd:
+ put_unused_fd(vb->out_fence_fd);
+ vb->out_fence_fd = -1;
+ return ret;
+}
+
/*
* vb2_start_streaming() - Attempt to start streaming.
* @q: videobuf2 queue
@@ -1463,7 +1539,7 @@ static void vb2_qbuf_fence_cb(struct dma_fence *f, struct dma_fence_cb *cb)
}

int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
- struct dma_fence *in_fence)
+ struct dma_fence *in_fence, bool out_fence)
{
struct vb2_buffer *vb;
unsigned long flags;
@@ -1496,6 +1572,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
list_add_tail(&vb->queued_entry, &q->queued_list);
q->queued_count++;
q->waiting_for_buffers = false;
+ q->queueing_started = 1;
vb->state = VB2_BUF_STATE_QUEUED;
vb->in_fence = in_fence;

@@ -1555,6 +1632,14 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,

spin_unlock_irqrestore(&vb->fence_cb_lock, flags);

+ if (out_fence) {
+ ret = vb2_setup_out_fence(q, vb);
+ if (ret) {
+ dprintk(1, "failed to set up out-fence\n");
+ goto err;
+ }
+ }
+
/* Fill buffer information for the userspace */
if (pb)
call_void_bufop(q, fill_user_buffer, vb, pb);
@@ -1818,6 +1903,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
q->start_streaming_called = 0;
q->queued_count = 0;
q->error = 0;
+ q->queueing_started = 0;

list_for_each_entry(vb, &q->queued_list, queued_entry) {
spin_lock_irqsave(&vb->fence_cb_lock, flags);
@@ -2170,6 +2256,7 @@ int vb2_core_queue_init(struct vb2_queue *q)
spin_lock_init(&q->done_lock);
mutex_init(&q->mmap_lock);
init_waitqueue_head(&q->done_wq);
+ spin_lock_init(&q->out_fence_lock);

q->memory = VB2_MEMORY_UNKNOWN;

@@ -2421,7 +2508,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
* Queue all buffers.
*/
for (i = 0; i < q->num_buffers; i++) {
- ret = vb2_core_qbuf(q, i, NULL, NULL);
+ ret = vb2_core_qbuf(q, i, NULL, NULL, false);
if (ret)
goto err_reqbufs;
fileio->bufs[i].queued = 1;
@@ -2600,7 +2687,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_

if (copy_timestamp)
b->timestamp = ktime_get_ns();
- ret = vb2_core_qbuf(q, index, NULL, NULL);
+ ret = vb2_core_qbuf(q, index, NULL, NULL, false);
dprintk(5, "vb2_dbuf result: %d\n", ret);
if (ret)
return ret;
@@ -2703,7 +2790,7 @@ static int vb2_thread(void *data)
if (copy_timestamp)
vb->timestamp = ktime_get_ns();
if (!threadio->stop)
- ret = vb2_core_qbuf(q, vb->index, NULL, NULL);
+ ret = vb2_core_qbuf(q, vb->index, NULL, NULL, false);
call_void_qop(q, wait_prepare, q);
if (ret || threadio->stop)
break;
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 74d7062e5285..41a88839683e 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -217,7 +217,11 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
b->sequence = vbuf->sequence;
b->reserved = 0;

- b->fence_fd = 0;
+ if (b->flags & V4L2_BUF_FLAG_OUT_FENCE)
+ b->fence_fd = vb->out_fence_fd;
+ else
+ b->fence_fd = 0;
+
if (vb->in_fence)
b->flags |= V4L2_BUF_FLAG_IN_FENCE;
else
@@ -496,6 +500,13 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
ret = __verify_planes_array(vb, b);
if (!ret)
vb2_core_querybuf(q, b->index, b);
+
+ /*
+ * Can't return a fence fd, because it only
+ * makes sense on the process that queued the buffer.
+ */
+ if (b->flags & (V4L2_BUF_FLAG_IN_FENCE | V4L2_BUF_FLAG_OUT_FENCE))
+ b->fence_fd = -1;
return ret;
}
EXPORT_SYMBOL(vb2_querybuf);
@@ -600,7 +611,8 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
}
}

- return vb2_core_qbuf(q, b->index, b, in_fence);
+ return vb2_core_qbuf(q, b->index, b, in_fence,
+ b->flags & V4L2_BUF_FLAG_OUT_FENCE);
}
EXPORT_SYMBOL_GPL(vb2_qbuf);

@@ -626,6 +638,12 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
*/
b->flags &= ~V4L2_BUF_FLAG_DONE;

+ /*
+ * Can't return a fence fd, because it only
+ * makes sense on the process that queued the buffer.
+ */
+ if (b->flags & (V4L2_BUF_FLAG_IN_FENCE | V4L2_BUF_FLAG_OUT_FENCE))
+ b->fence_fd = -1;
return ret;
}
EXPORT_SYMBOL_GPL(vb2_dqbuf);
diff --git a/drivers/media/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
index 7da53f10db1a..053803c9ff45 100644
--- a/drivers/media/dvb-core/dvb_vb2.c
+++ b/drivers/media/dvb-core/dvb_vb2.c
@@ -385,7 +385,7 @@ int dvb_vb2_qbuf(struct dvb_vb2_ctx *ctx, struct dmx_buffer *b)
{
int ret;

- ret = vb2_core_qbuf(&ctx->vb_q, b->index, b, NULL);
+ ret = vb2_core_qbuf(&ctx->vb_q, b->index, b, NULL, false);
if (ret) {
dprintk(1, "[%s] index=%d errno=%d\n", ctx->name,
b->index, ret);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 28ce8f66882e..794140fcb5cf 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -260,6 +260,9 @@ struct vb2_buffer {
* using the buffer (queueing to the driver)
* fence_cb: fence callback information
* fence_cb_lock: protect callback signal/remove
+ * out_fence_fd: the out_fence_fd to be shared with userspace.
+ * out_fence: the out-fence associated with the buffer once
+ * it is queued to the driver.
*/
enum vb2_buffer_state state;

@@ -271,6 +274,9 @@ struct vb2_buffer {
struct dma_fence_cb fence_cb;
spinlock_t fence_cb_lock;

+ int out_fence_fd;
+ struct dma_fence *out_fence;
+
#ifdef CONFIG_VIDEO_ADV_DEBUG
/*
* Counters for how often these buffer-related ops are
@@ -533,6 +539,9 @@ struct vb2_buf_ops {
* @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
* last decoded buffer was already dequeued. Set for capture queues
* when a buffer with the %V4L2_BUF_FLAG_LAST is dequeued.
+ * @queueing_started: if queueing has started. Currently used to determine
+ * if an out_fence_context is needed.
+ * @out_fence_context: the fence context for the out fences
* @fileio: file io emulator internal data, used only if emulator is active
* @threadio: thread io internal data, used only if thread is active
*/
@@ -586,6 +595,10 @@ struct vb2_queue {
unsigned int is_output:1;
unsigned int copy_timestamp:1;
unsigned int last_buffer_dequeued:1;
+ unsigned int queueing_started:1;
+
+ u64 out_fence_context;
+ spinlock_t out_fence_lock;

struct vb2_fileio_data *fileio;
struct vb2_threadio_data *threadio;
@@ -784,6 +797,7 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
* @pb: buffer structure passed from userspace to
* v4l2_ioctl_ops->vidioc_qbuf handler in driver
* @in_fence: in-fence to wait on before queueing the buffer
+ * @out_fence: create an out-fence as a part of the queue operation
*
* Videobuf2 core helper to implement VIDIOC_QBUF() operation. It is called
* internally by VB2 by an API-specific handler, like ``videobuf2-v4l2.h``.
@@ -799,7 +813,7 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
* Return: returns zero on success; an error code otherwise.
*/
int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
- struct dma_fence *in_fence);
+ struct dma_fence *in_fence, bool out_fence);

/**
* vb2_core_dqbuf() - Dequeue a buffer to the userspace
--
2.16.3