Messages in this thread Patch in this message | | | Date | Wed, 25 Oct 2017 15:49:08 +0100 | From | Brian Starkey <> | Subject | Re: [RFC v4 13/17] [media] vb2: add in-fence support to QBUF |
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Hi Gustavo,
On Fri, Oct 20, 2017 at 07:50:08PM -0200, Gustavo Padovan wrote: >From: Gustavo Padovan <gustavo.padovan@collabora.com> > >Receive in-fence from userspace and add support for waiting on them >before queueing the buffer to the driver. Buffers are only queued >to the driver once they are ready. A buffer is ready when its >in-fence signals. > >For queues that require vb2 to queue buffers to the v4l2 driver in same >order they are received from userspace we use fence_array to keep that >ordering. Basically we create a fence_array that contains both the current >fence and the fence from the previous buffer (which might be a fence array >as well). The base fence class for the fence_array becomes the new buffer >fence, waiting on that one guarantees that it won't be queued out of >order.
The API sounds/looks good to me, makes sense to let driver opt in/out via the ordered_in_vb2 thing. Thanks for implementing it!
> >v5: - use fence_array to keep buffers ordered in vb2 core when > needed (Brian Stark) > - keep backward compatibility on the reserved2 field (Brian Stark) > - protect fence callback removal with lock (Brian Stark)
Brian Starkey, but close ;-)
> >v4: > - Add a comment about dma_fence_add_callback() not returning a > error (Hans) > - Call dma_fence_put(vb->in_fence) if fence signaled (Hans) > - select SYNC_FILE under config VIDEOBUF2_CORE (Hans) > - Move dma_fence_is_signaled() check to __enqueue_in_driver() (Hans) > - Remove list_for_each_entry() in __vb2_core_qbuf() (Hans) > - Remove if (vb->state != VB2_BUF_STATE_QUEUED) from > vb2_start_streaming() (Hans) > - set IN_FENCE flags on __fill_v4l2_buffer (Hans) > - Queue buffers to the driver as soon as they are ready (Hans) > - call fill_user_buffer() after queuing the buffer (Hans) > - add err: label to clean up fence > - add dma_fence_wait() before calling vb2_start_streaming() > >v3: - document fence parameter > - remove ternary if at vb2_qbuf() return (Mauro) > - do not change if conditions behaviour (Mauro) > >v2: > - fix vb2_queue_or_prepare_buf() ret check > - remove check for VB2_MEMORY_DMABUF only (Javier) > - check num of ready buffers to start streaming > - when queueing, start from the first ready buffer > - handle queue cancel > >Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com> >--- > drivers/media/v4l2-core/Kconfig | 1 + > drivers/media/v4l2-core/videobuf2-core.c | 179 ++++++++++++++++++++++++++++--- > drivers/media/v4l2-core/videobuf2-v4l2.c | 29 ++++- > include/media/videobuf2-core.h | 17 ++- > 4 files changed, 208 insertions(+), 18 deletions(-) > >diff --git a/drivers/media/v4l2-core/Kconfig b/drivers/media/v4l2-core/Kconfig >index a35c33686abf..3f988c407c80 100644 >--- a/drivers/media/v4l2-core/Kconfig >+++ b/drivers/media/v4l2-core/Kconfig >@@ -83,6 +83,7 @@ config VIDEOBUF_DVB > # Used by drivers that need Videobuf2 modules > config VIDEOBUF2_CORE > select DMA_SHARED_BUFFER >+ select SYNC_FILE > tristate > > config VIDEOBUF2_MEMOPS >diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c >index 60f8b582396a..78f369dba3e3 100644 >--- a/drivers/media/v4l2-core/videobuf2-core.c >+++ b/drivers/media/v4l2-core/videobuf2-core.c >@@ -346,6 +346,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory, > vb->index = q->num_buffers + buffer; > vb->type = q->type; > vb->memory = memory; >+ spin_lock_init(&vb->fence_cb_lock); > for (plane = 0; plane < num_planes; ++plane) { > vb->planes[plane].length = plane_sizes[plane]; > vb->planes[plane].min_length = plane_sizes[plane]; >@@ -1222,6 +1223,9 @@ static void __enqueue_in_driver(struct vb2_buffer *vb) > { > struct vb2_queue *q = vb->vb2_queue; > >+ if (vb->in_fence && !dma_fence_is_signaled(vb->in_fence)) >+ return; >+ > vb->state = VB2_BUF_STATE_ACTIVE; > atomic_inc(&q->owned_by_drv_count); > >@@ -1273,6 +1277,20 @@ static int __buf_prepare(struct vb2_buffer *vb, const void *pb) > return 0; > } > >+static int __get_num_ready_buffers(struct vb2_queue *q) >+{ >+ struct vb2_buffer *vb; >+ int ready_count = 0; >+ >+ /* count num of buffers ready in front of the queued_list */ >+ list_for_each_entry(vb, &q->queued_list, queued_entry) { >+ if (!vb->in_fence || dma_fence_is_signaled(vb->in_fence)) >+ ready_count++;
I think there's still some races on vb->in_fence. Couldn't the callback on any of the buffers in the queued_list have their callback run at any moment?
That could make this loop do bad things, and similarly the loop in vb2_start_streaming() which calls __enqueue_in_driver().
>+ } >+ >+ return ready_count; >+} >+ > int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb) > { > struct vb2_buffer *vb; >@@ -1361,7 +1379,74 @@ static int vb2_start_streaming(struct vb2_queue *q) > return ret; > } > >-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb) >+static struct dma_fence *__set_in_fence(struct vb2_queue *q, >+ struct vb2_buffer *vb, >+ struct dma_fence *fence) >+{ >+ if (q->last_fence && dma_fence_is_signaled(q->last_fence)) { >+ dma_fence_put(q->last_fence); >+ q->last_fence = NULL; >+ } >+ >+ /* For drivers that require the ordering of buffers queued from >+ * userspace to be the same it is queued to the driver - output >+ * some m2m devices - we create a fence array with the fence from >+ * the last queued buffer and this one, that way the fence for this >+ * buffer can't signal before the last one. >+ */ >+ if (q->is_output || q->ordered_in_vb2) {
Just a stylistic thing - you could invert this conditional and return early, saving a level of indentation below.
>+ if (fence && q->last_fence) { >+ struct dma_fence **fences; >+ struct dma_fence_array *arr; >+ >+ fences = kcalloc(2, sizeof(*fences), GFP_KERNEL); >+ if (!fences) >+ return ERR_PTR(-ENOMEM); >+ >+ fences[0] = fence; >+ fences[1] = q->last_fence; >+ >+ arr = dma_fence_array_create(2, fences, >+ dma_fence_context_alloc(1), >+ 1, false);
I'm not sure if it's right to get a new fence_context every time here. The comment on dma_fence_context_counter sounds like the vb2_queue should have a single context of its own.
>+ if (!arr) { >+ kfree(fences); >+ return ERR_PTR(-ENOMEM); >+ } >+ >+ fence = &arr->base; >+ } else if (!fence && q->last_fence) { >+ fence = dma_fence_get(q->last_fence); >+ } >+ >+ q->last_fence = dma_fence_get(fence);
Seems like the refcounting isn't quite right here.
If you land in "else if (!fence && q->last_fence)", then "fence" gets a new reference to q->last_fence, and you take another one here - which looks like one too many.
I _think_ the right thing to do is just give the previous reference on q->last_fence to "fence", without taking a new one:
} else if (!fence && q->last_fence) { fence = q->last_fence; }
That's analogous to the other path where fence is not-NULL, and the fence-array takes ownership of the existing references on fence and q->last_fence, without taking new references.
Please double check my logic though!
>+ } >+ >+ return fence; >+} >+ >+static void vb2_qbuf_fence_cb(struct dma_fence *f, struct dma_fence_cb *cb) >+{ >+ struct vb2_buffer *vb = container_of(cb, struct vb2_buffer, fence_cb); >+ struct vb2_queue *q = vb->vb2_queue; >+ unsigned long flags; >+ >+ spin_lock_irqsave(&vb->fence_cb_lock, flags); >+ if (!vb->in_fence) { >+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags); >+ return; >+ } >+ >+ dma_fence_put(vb->in_fence); >+ vb->in_fence = NULL; >+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags); >+ >+ if (q->start_streaming_called) >+ __enqueue_in_driver(vb); >+} >+ >+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb, >+ struct dma_fence *fence) > { > struct vb2_buffer *vb; > int ret; >@@ -1372,16 +1457,18 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb) > case VB2_BUF_STATE_DEQUEUED: > ret = __buf_prepare(vb, pb); > if (ret) >- return ret; >+ goto err; > break; > case VB2_BUF_STATE_PREPARED: > break; > case VB2_BUF_STATE_PREPARING: > dprintk(1, "buffer still being prepared\n"); >- return -EINVAL; >+ ret = -EINVAL; >+ goto err; > default: > dprintk(1, "invalid buffer state %d\n", vb->state); >- return -EINVAL; >+ ret = -EINVAL; >+ goto err; > } > > /* >@@ -1398,30 +1485,75 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb) > > trace_vb2_qbuf(q, vb); > >+ vb->in_fence = __set_in_fence(q, vb, fence); >+ if (IS_ERR(vb->in_fence)) { >+ ret = PTR_ERR(vb->in_fence); >+ goto err;
Between here, __set_in_fence() and vb2_qbuf() there's a reference leaked on "fence" in the case of error. I'm not sure what semantics you'd like, but it should be clear whose responsibility it is to clear up "fence" if __set_in_fence() fails (at the moment, looks like no-one does).
>+ }
... and if __set_in_fence() succeeds, then vb->in_fence now owns the reference on "fence" that was passed in, so I guess you should set fence = NULL here.
>+ >+ /* >+ * If it is time to call vb2_start_streaming() wait for the fence >+ * to signal first. Of course, this happens only once per streaming. >+ * We want to run any step that might fail before we set the callback >+ * to queue the fence when it signals. >+ */ >+ if (fence && !q->start_streaming_called &&
I think this should be vb->in_fence now, and the same for all further uses of "fence" in this function.
>+ __get_num_ready_buffers(q) == q->min_buffers_needed - 1) >+ dma_fence_wait(fence, true); >+ > /* > * If streamon has been called, and we haven't yet called > * start_streaming() since not enough buffers were queued, and > * we now have reached the minimum number of queued buffers, > * then we can finally call start_streaming(). >- * >- * If already streaming, give the buffer to driver for processing. >- * If not, the buffer will be given to driver on next streamon. > */ > if (q->streaming && !q->start_streaming_called && >- q->queued_count >= q->min_buffers_needed) { >+ __get_num_ready_buffers(q) >= q->min_buffers_needed) { > ret = vb2_start_streaming(q); > if (ret) >- return ret; >- } else if (q->start_streaming_called) { >- __enqueue_in_driver(vb); >+ goto err; >+ } >+ >+ /* >+ * For explicit synchronization: If the fence didn't signal >+ * yet we setup a callback to queue the buffer once the fence >+ * signals, and then, return successfully. But if the fence >+ * already signaled we lose the reference we held and queue the >+ * buffer to the driver. >+ */ >+ if (fence) { >+ ret = dma_fence_add_callback(fence, &vb->fence_cb, >+ vb2_qbuf_fence_cb); >+ if (!ret) >+ goto fill;
Just spotted that you should probably handle the -EINVAL case here and jump to err.
>+ >+ dma_fence_put(fence); >+ vb->in_fence = NULL; > } > >+fill: >+ /* >+ * If already streaming and there is no fence to wait on >+ * give the buffer to driver for processing. >+ */ >+ if (q->start_streaming_called && !vb->in_fence) >+ __enqueue_in_driver(vb);
The callback could have run just before this, clearing vb->in_fence and ending up with __enqueue_in_driver() getting called twice.
>+ > /* Fill buffer information for the userspace */ > if (pb) > call_void_bufop(q, fill_user_buffer, vb, pb); > > dprintk(2, "qbuf of buffer %d succeeded\n", vb->index); > return 0; >+ >+err: >+ if (vb->in_fence) { >+ dma_fence_put(vb->in_fence); >+ vb->in_fence = NULL; >+ } >+ >+ return ret; >+ > } > EXPORT_SYMBOL_GPL(vb2_core_qbuf); > >@@ -1632,6 +1764,8 @@ EXPORT_SYMBOL_GPL(vb2_core_dqbuf); > static void __vb2_queue_cancel(struct vb2_queue *q) > { > unsigned int i; >+ struct vb2_buffer *vb; >+ unsigned long flags; > > /* > * Tell driver to stop all transactions and release all queued >@@ -1659,6 +1793,21 @@ static void __vb2_queue_cancel(struct vb2_queue *q) > q->queued_count = 0; > q->error = 0; > >+ list_for_each_entry(vb, &q->queued_list, queued_entry) { >+ spin_lock_irqsave(&vb->fence_cb_lock, flags); >+ if (vb->in_fence) { >+ dma_fence_remove_callback(vb->in_fence, &vb->fence_cb); >+ dma_fence_put(vb->in_fence); >+ vb->in_fence = NULL; >+ } >+ spin_unlock_irqrestore(&vb->fence_cb_lock, flags); >+ } >+ >+ if (q->last_fence) { >+ dma_fence_put(q->last_fence); >+ q->last_fence = NULL; >+ } >+ > /* > * Remove all buffers from videobuf's list... > */ >@@ -1720,7 +1869,7 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type) > * Tell driver to start streaming provided sufficient buffers > * are available. > */ >- if (q->queued_count >= q->min_buffers_needed) { >+ if (__get_num_ready_buffers(q) >= q->min_buffers_needed) { > ret = v4l_vb2q_enable_media_source(q); > if (ret) > return ret; >@@ -2240,7 +2389,7 @@ 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); >+ ret = vb2_core_qbuf(q, i, NULL, NULL); > if (ret) > goto err_reqbufs; > fileio->bufs[i].queued = 1; >@@ -2419,7 +2568,7 @@ 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); >+ ret = vb2_core_qbuf(q, index, NULL, NULL); > dprintk(5, "vb2_dbuf result: %d\n", ret); > if (ret) > return ret; >@@ -2522,7 +2671,7 @@ 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); >+ ret = vb2_core_qbuf(q, vb->index, NULL, NULL); > call_void_qop(q, wait_prepare, q); > if (ret || threadio->stop) > break; >diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c >index 110fb45fef6f..4c09ea007d90 100644 >--- a/drivers/media/v4l2-core/videobuf2-v4l2.c >+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c >@@ -23,6 +23,7 @@ > #include <linux/sched.h> > #include <linux/freezer.h> > #include <linux/kthread.h> >+#include <linux/sync_file.h> > > #include <media/v4l2-dev.h> > #include <media/v4l2-fh.h> >@@ -178,6 +179,12 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b, > return -EINVAL; > } > >+ if ((b->fence_fd != 0 && b->fence_fd != -1) && >+ !(b->flags & V4L2_BUF_FLAG_IN_FENCE)) { >+ dprintk(1, "%s: fence_fd set without IN_FENCE flag\n", opname); >+ return -EINVAL; >+ } >+ > return __verify_planes_array(q->bufs[b->index], b); > } > >@@ -203,9 +210,14 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb) > b->timestamp = ns_to_timeval(vb->timestamp); > b->timecode = vbuf->timecode; > b->sequence = vbuf->sequence; >- b->fence_fd = -1; > b->reserved = 0; > >+ b->fence_fd = -1; >+ if (vb->in_fence) >+ b->flags |= V4L2_BUF_FLAG_IN_FENCE; >+ else >+ b->flags &= ~V4L2_BUF_FLAG_IN_FENCE; >+ > if (q->is_multiplanar) { > /* > * Fill in plane-related data if userspace provided an array >@@ -560,6 +572,7 @@ EXPORT_SYMBOL_GPL(vb2_create_bufs); > > int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b) > { >+ struct dma_fence *fence = NULL; > int ret; > > if (vb2_fileio_is_active(q)) { >@@ -568,7 +581,19 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b) > } > > ret = vb2_queue_or_prepare_buf(q, b, "qbuf"); >- return ret ? ret : vb2_core_qbuf(q, b->index, b); >+ if (ret) >+ return ret; >+ >+ if (b->flags & V4L2_BUF_FLAG_IN_FENCE) { >+ fence = sync_file_get_fence(b->fence_fd);
In DRM a fence_fd of -1 means "already signaled" - should that be allowed here too?
Cheers, -Brian
>+ if (!fence) { >+ dprintk(1, "failed to get in-fence from fd %d\n", >+ b->fence_fd); >+ return -EINVAL; >+ } >+ } >+ >+ return vb2_core_qbuf(q, b->index, b, fence); > } > EXPORT_SYMBOL_GPL(vb2_qbuf); > >diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h >index fc333e10e7d8..624ca2dce9ea 100644 >--- a/include/media/videobuf2-core.h >+++ b/include/media/videobuf2-core.h >@@ -16,6 +16,7 @@ > #include <linux/mutex.h> > #include <linux/poll.h> > #include <linux/dma-buf.h> >+#include <linux/dma-fence.h> > > #define VB2_MAX_FRAME (32) > #define VB2_MAX_PLANES (8) >@@ -254,11 +255,20 @@ struct vb2_buffer { > * all buffers queued from userspace > * done_entry: entry on the list that stores all buffers ready > * to be dequeued to userspace >+ * in_fence: fence receive from vb2 client to wait on before >+ * using the buffer (queueing to the driver) >+ * fence_cb: fence callback information >+ * fence_cb_lock: protect callback signal/remove > */ > enum vb2_buffer_state state; > > struct list_head queued_entry; > struct list_head done_entry; >+ >+ struct dma_fence *in_fence; >+ struct dma_fence_cb fence_cb; >+ spinlock_t fence_cb_lock; >+ > #ifdef CONFIG_VIDEO_ADV_DEBUG > /* > * Counters for how often these buffer-related ops are >@@ -508,6 +518,7 @@ struct vb2_buf_ops { > * @ordered_in_vb2: set by the driver to tell vb2 te guarantee the order > * of buffer queue from userspace with QBUF() until they are > * queued to the driver. >+ * @last_fence: last in-fence received. Used to keep ordering. > * @fileio: file io emulator internal data, used only if emulator is active > * @threadio: thread io internal data, used only if thread is active > */ >@@ -563,6 +574,8 @@ struct vb2_queue { > unsigned int ordered_in_driver:1; > unsigned int ordered_in_vb2:1; > >+ struct dma_fence *last_fence; >+ > struct vb2_fileio_data *fileio; > struct vb2_threadio_data *threadio; > >@@ -738,6 +751,7 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb); > * @index: id number of the buffer > * @pb: buffer structure passed from userspace to vidioc_qbuf handler > * in driver >+ * @fence: in-fence to wait on before queueing the buffer > * > * Should be called from vidioc_qbuf ioctl handler of a driver. > * The passed buffer should have been verified. >@@ -752,7 +766,8 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb); > * The return values from this function are intended to be directly returned > * from vidioc_qbuf handler in driver. > */ >-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb); >+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb, >+ struct dma_fence *fence); > > /** > * vb2_core_dqbuf() - Dequeue a buffer to the userspace >-- >2.13.6 >
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