2021-04-13 11:01:47

by Pedro Tammela

Subject: [PATCH bpf-next v2] libbpf: clarify flags in ringbuf helpers

In 'bpf_ringbuf_reserve()' we require the flag to '0' at the moment.

For 'bpf_ringbuf_{discard,submit,output}' a flag of '0' might send a
notification to the process if needed.

Signed-off-by: Pedro Tammela <[email protected]>
---
include/uapi/linux/bpf.h | 16 ++++++++++++++++
tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 49371eba98ba..24593fd72f9d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4061,12 +4061,20 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * An adaptive notification is a notification sent whenever the user-space
+ * process has caught up and consumed all available payloads. In case the user-space
+ * process is still processing a previous payload, then no notification is needed
+ * as it will process the newly added payload automatically.
* Return
* 0 on success, or a negative error in case of failure.
*
* void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
* Description
* Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * *flags* must be 0.
* Return
* Valid pointer with *size* bytes of memory available; NULL,
* otherwise.
@@ -4078,6 +4086,10 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * See 'bpf_ringbuf_output()' for the definition of adaptive notification.
* Return
* Nothing. Always succeeds.
*
@@ -4088,6 +4100,10 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * See 'bpf_ringbuf_output()' for the definition of adaptive notification.
* Return
* Nothing. Always succeeds.
*
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 69902603012c..8debc8280f3e 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4061,12 +4061,20 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * An adaptive notification is a notification sent whenever the user-space
+ * process has caught up and consumed all available payloads. In case the user-space
+ * process is still processing a previous payload, then no notification is needed
+ * as it will process the newly added payload automatically.
* Return
* 0 on success, or a negative error in case of failure.
*
* void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
* Description
* Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * *flags* must be 0.
* Return
* Valid pointer with *size* bytes of memory available; NULL,
* otherwise.
@@ -4078,6 +4086,10 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * See 'bpf_ringbuf_output()' for the definition of adaptive notification.
* Return
* Nothing. Always succeeds.
*
@@ -4088,6 +4100,10 @@ union bpf_attr {
* of new data availability is sent.
* If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
* of new data availability is sent unconditionally.
+ * If **0** is specified in *flags*, an adaptive notification
+ * of new data availability is sent.
+ *
+ * See 'bpf_ringbuf_output()' for the definition of adaptive notification.
* Return
* Nothing. Always succeeds.
*
--
2.25.1

2021-04-13 12:31:53

by Andrii Nakryiko

Subject: Re: [PATCH bpf-next v2] libbpf: clarify flags in ringbuf helpers

On Mon, Apr 12, 2021 at 12:25 PM Pedro Tammela <[email protected]> wrote:
>
> In 'bpf_ringbuf_reserve()' we require the flag to '0' at the moment.
>
> For 'bpf_ringbuf_{discard,submit,output}' a flag of '0' might send a
> notification to the process if needed.
>
> Signed-off-by: Pedro Tammela <[email protected]>
> ---

Great, thanks! Applied to bpf-next.

> include/uapi/linux/bpf.h | 16 ++++++++++++++++
> tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
> 2 files changed, 32 insertions(+)
>

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