From 5c507329000e282dce91e6c98ee6ffa61a8a5e49 Mon Sep 17 00:00:00 2001
From: Pedro Tammela <pctammela@gmail.com>
Date: Mon, 12 Apr 2021 16:24:32 -0300
Subject: [PATCH] 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 <pctammela@mojatatu.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210412192434.944343-1-pctammela@mojatatu.com
---
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 e1ee1be7e49b1..85c924bc21b1f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4082,12 +4082,20 @@ 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.
@@ -4099,6 +4107,10 @@ 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.
*
@@ -4109,6 +4121,10 @@ 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 e1ee1be7e49b1..85c924bc21b1f 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4082,12 +4082,20 @@ 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.
@@ -4099,6 +4107,10 @@ 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.
*
@@ -4109,6 +4121,10 @@ 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.
*
--
2.30.2