On 6/3/26 18:19, Borislav Petkov wrote:
> On Wed, Jun 03, 2026 at 12:17:07PM -0400, Steven Rostedt wrote:
>> On Wed, 3 Jun 2026 15:44:54 +0200
>> "David Hildenbrand (Arm)" <[email protected]> wrote:
>>
>>> Likely the latter. BPF [1] documents:
>>>
>>> Q: Are tracepoints part of the stable ABI?
>>> A: NO. Tracepoints are tied to internal implementation details hence they
>>> are
>>> subject to change and can break with newer kernels. BPF programs need to
>>> change
>>> accordingly when this happens.
>>>
>>> The Kernel ABI document explicitly doesn't list them AFAIKS.
>>>
>>> There were previous discussions on the stability of tracepints [2], I don't
>>> know
>>> what changed in the meantime. CCing Steve
>>>
>>> [1] https://www.kernel.org/doc/html/latest/bpf/bpf_design_QA.html
>>> [2] https://lwn.net/Articles/747256/
>>> [3] https://www.kernel.org/doc/html/latest/admin-guide/abi.html
>>
>> Tracepoints are not stable or BPF programs only. But other applications
>> they are[1].
>>
>> Adding Linus as he's the Supreme Judge on the matter.
>
> I *think* tools or libtraceevent can't really anticipate the TP namespace
> change so we might have to revert, I'm afraid...
Yeah, I was fearing that when I read in [2]:
"It has become clear in the past that this promise extends to
tracepoints, most notably in 2011 when a tracepoint change broke
powertop and had to be reverted."
Which means that I now also fully understand
"Some kernel maintainers prohibit or severely restrict the addition of
tracepoints to their subsystems out of fear that a similar thing could
happen to them. "
Whatever the result of this discussion will be, I'll try to document it.
--
Cheers,
David
