[bpf-next,05/14] libbpf: add ring__producer_pos, ring__consumer_pos

Commit Message

Martin Kelly Sept. 14, 2023, 11:11 p.m. UTC

Add APIs to get the producer and consumer position for a given
ringbuffer.

Signed-off-by: Martin Kelly <[e-mail]>
---
 tools/lib/bpf/libbpf.h   | 16 ++++++++++++++++
 tools/lib/bpf/libbpf.map |  2 ++
 tools/lib/bpf/ringbuf.c  | 14 ++++++++++++++
 3 files changed, 32 insertions(+)

Comments

Andrii Nakryiko Sept. 21, 2023, 1:28 a.m. UTC | #1

On Thu, Sep 14, 2023 at 4:12 PM Martin Kelly
<[e-mail]> wrote:
>
> Add APIs to get the producer and consumer position for a given
> ringbuffer.
>
> Signed-off-by: Martin Kelly <[e-mail]>
> ---
>  tools/lib/bpf/libbpf.h   | 16 ++++++++++++++++
>  tools/lib/bpf/libbpf.map |  2 ++
>  tools/lib/bpf/ringbuf.c  | 14 ++++++++++++++
>  3 files changed, 32 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 2d6c39e20863..935162dbb3bf 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -1263,6 +1263,22 @@ LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
>  LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
>                                           unsigned int idx);
>
> +/**
> + * @brief **ring__consumer_pos()** returns the current consumer position.
> + *
> + * @param r A ring object.
> + * @return The current consumer position.
> + */
> +LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
> +
> +/**
> + * @brief **ring__producer_pos()** returns the current producer position.
> + *
> + * @param r A ring object.
> + * @return The current producer position.
> + */
> +LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
> +
>  struct user_ring_buffer_opts {
>         size_t sz; /* size of this struct, for forward/backward compatibility */
>  };
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 7a7370c2bc25..1c532fe7a445 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -401,4 +401,6 @@ LIBBPF_1.3.0 {
>                 bpf_program__attach_tcx;
>                 bpf_program__attach_uprobe_multi;
>                 ring_buffer__ring;
> +               ring__consumer_pos;
> +               ring__producer_pos;

we keep this list ordered, so ring__ goes before ring_b



>  } LIBBPF_1.2.0;
> diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
> index 2857df0f2d03..54c596db57a4 100644
> --- a/tools/lib/bpf/ringbuf.c
> +++ b/tools/lib/bpf/ringbuf.c
> @@ -336,6 +336,20 @@ struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
>         return rb->rings[idx];
>  }
>
> +unsigned long ring__consumer_pos(const struct ring *r)
> +{
> +       /* Synchronizes with smp_store_release() in ringbuf_process_ring(). */
> +       return smp_load_acquire(r->consumer_pos);
> +}
> +
> +unsigned long ring__producer_pos(const struct ring *r)
> +{
> +       /* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in
> +        * the kernel.
> +        */
> +       return smp_load_acquire(r->producer_pos);
> +}
> +
>  static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
>  {
>         if (rb->consumer_pos) {
> --
> 2.34.1
>

Patch

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2d6c39e20863..935162dbb3bf 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1263,6 +1263,22 @@  LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
 LIBBPF_API struct ring *ring_buffer__ring(struct ring_buffer *rb,
 					  unsigned int idx);
 
+/**
+ * @brief **ring__consumer_pos()** returns the current consumer position.
+ *
+ * @param r A ring object.
+ * @return The current consumer position.
+ */
+LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
+
+/**
+ * @brief **ring__producer_pos()** returns the current producer position.
+ *
+ * @param r A ring object.
+ * @return The current producer position.
+ */
+LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
+
 struct user_ring_buffer_opts {
 	size_t sz; /* size of this struct, for forward/backward compatibility */
 };
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 7a7370c2bc25..1c532fe7a445 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -401,4 +401,6 @@  LIBBPF_1.3.0 {
 		bpf_program__attach_tcx;
 		bpf_program__attach_uprobe_multi;
 		ring_buffer__ring;
+		ring__consumer_pos;
+		ring__producer_pos;
 } LIBBPF_1.2.0;
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 2857df0f2d03..54c596db57a4 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -336,6 +336,20 @@  struct ring *ring_buffer__ring(struct ring_buffer *rb, unsigned int idx)
 	return rb->rings[idx];
 }
 
+unsigned long ring__consumer_pos(const struct ring *r)
+{
+	/* Synchronizes with smp_store_release() in ringbuf_process_ring(). */
+	return smp_load_acquire(r->consumer_pos);
+}
+
+unsigned long ring__producer_pos(const struct ring *r)
+{
+	/* Synchronizes with smp_store_release() in __bpf_ringbuf_reserve() in
+	 * the kernel.
+	 */
+	return smp_load_acquire(r->producer_pos);
+}
+
 static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
 {
 	if (rb->consumer_pos) {