Re: [PATCH bpf-next v8 1/3] perf: Add rctx in perf_callchain_entry

[Tao Chen <chen.dylane@linux.dev>]

在 2026/1/29 02:59, Andrii Nakryiko 写道:
> On Wed, Jan 28, 2026 at 8:53 AM Tao Chen <chen.dylane@linux.dev> wrote:
>>
>> 在 2026/1/28 16:59, Peter Zijlstra 写道:
>>> On Mon, Jan 26, 2026 at 03:43:29PM +0800, Tao Chen wrote:
>>>> Record rctx inside the perf_callchain_entry itself, when callers of
>>>> get_callchain_entry no longer care about the assignment of rctx, and
>>>> will be used in the next patch.
>>>
>>> Sorry, what?
>>>
>>> The recursion context is very much about the caller, and very much not
>>> about the data. This just doesn't make sense.
>>
>> Well, Andrii, it seems we have to go back to the original way.
> 
> Huh, why? Peter is confused by your wording, he didn't say that what
> you are doing is broken.
>

I see, will update the changelog, thanks.
> The point is to couple rctx with the exact perf_callchain_entry
> returned to the caller in that recursion context. There is no
> contradiction.
> 
> It's purely about simplifying the interface. While previously the
> caller would have to juggle perf_callchain_entry and rctx separately
> (but still ensure that entry and rctx do match each other when calling
> put_callchain_entry), now it's more convenient and less error-prone
> because returned entry will record rctx it was retrieved with.
> 
> That perf_callchain_entry should not be reused by anyone else between
> successful get_callchain_entry and put_callchain_entry, so there is no
> problem here.
> 
>>
>> --
>> Best Regards
>> Tao Chen


-- 
Best Regards
Tao Chen