linux-kernel - Re: [PATCH bpf-next v6 2/2] bpf: Hold the perf callchain entry until used completely

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Message-ID: <CAADnVQ+pP2oJhMOWe1dLg4W_+bMU=amfzYGWKJ4yVNcq4KOvNA@mail.gmail.com>
Date: Tue, 16 Dec 2025 15:35:08 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Tao Chen <chen.dylane@...ux.dev>
Cc: Yonghong Song <yonghong.song@...ux.dev>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, "linux-perf-use." <linux-perf-users@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v6 2/2] bpf: Hold the perf callchain entry until
 used completely

On Wed, Dec 3, 2025 at 1:34 AM Tao Chen <chen.dylane@...ux.dev> wrote:
>
> 在 2025/11/26 17:29, Tao Chen 写道:
> > 在 2025/11/14 00:01, Yonghong Song 写道:
> >>
> >>
> >> On 11/12/25 8:31 AM, Tao Chen wrote:
> >>> As Alexei noted, get_perf_callchain() return values may be reused
> >>> if a task is preempted after the BPF program enters migrate disable
> >>> mode. The perf_callchain_entres has a small stack of entries, and
> >>> we can reuse it as follows:
> >>>
> >>> 1. get the perf callchain entry
> >>> 2. BPF use...
> >>> 3. put the perf callchain entry
> >>>
> >>> And Peter suggested that get_recursion_context used with preemption
> >>> disabled, so we should disable preemption at BPF side.
> >>>
> >>> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
> >>
> >> Acked-by: Yonghong Song <yonghong.song@...ux.dev>
> >>
> >
> > Hi eBPF maintainers,
> >
> > This patch appears to have missed the eBPF maintainers on the list,
> > please review it again, thanks.
> >
>
> ping...

pls resubmit and ask Peter to ack that your patches match what he suggested.