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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
This commit is contained in:
Pedro Tammela 2021-04-12 16:24:32 -03:00 committed by Andrii Nakryiko
parent aadb2bb83f
commit 5c50732900
2 changed files with 32 additions and 0 deletions
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16
include/uapi/linux/bpf.h
View File

@ -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.
*

16
tools/include/uapi/linux/bpf.h
View File

@ -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.
*