From: Peter Zijlstra <peterz@infradead.org>
To: Tao Chen <chen.dylane@linux.dev>
Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org,
mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com,
kan.liang@linux.intel.com, song@kernel.org, ast@kernel.org,
daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev,
eddyz87@gmail.com, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, linux-perf-users@vger.kernel.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v8 2/3] perf: Refactor get_perf_callchain
Date: Wed, 28 Jan 2026 10:10:33 +0100 [thread overview]
Message-ID: <20260128091033.GG3372621@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260126074331.815684-3-chen.dylane@linux.dev>
On Mon, Jan 26, 2026 at 03:43:30PM +0800, Tao Chen wrote:
> From BPF stack map, we want to ensure that the callchain buffer
> will not be overwritten by other preemptive tasks and we also aim
> to reduce the preempt disable interval, Based on the suggestions from Peter
> and Andrrii, export new API __get_perf_callchain and the usage scenarios
> are as follows from BPF side:
>
> preempt_disable()
> entry = get_callchain_entry()
> preempt_enable()
> __get_perf_callchain(entry)
> put_callchain_entry(entry)
That makes no sense, this means any other task on that CPU is getting
screwed over.
Why are you worried about the preempt_disable() here? If this were an
interrupt context we'd still do that unwind -- but then with IRQs
disabled.
next prev parent reply other threads:[~2026-01-28 9:10 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-26 7:43 [PATCH bpf-next v8 0/3] Pass external callchain entry to get_perf_callchain Tao Chen
2026-01-26 7:43 ` [PATCH bpf-next v8 1/3] perf: Add rctx in perf_callchain_entry Tao Chen
2026-01-26 8:03 ` bot+bpf-ci
2026-01-26 8:51 ` Tao Chen
2026-01-27 21:01 ` Andrii Nakryiko
2026-01-28 2:41 ` Tao Chen
2026-01-28 8:59 ` Peter Zijlstra
2026-01-28 16:52 ` Tao Chen
2026-01-28 18:59 ` Andrii Nakryiko
2026-01-29 3:03 ` Tao Chen
2026-01-26 7:43 ` [PATCH bpf-next v8 2/3] perf: Refactor get_perf_callchain Tao Chen
2026-01-27 21:07 ` Andrii Nakryiko
2026-01-28 2:42 ` Tao Chen
2026-01-28 9:10 ` Peter Zijlstra [this message]
2026-01-28 16:49 ` Tao Chen
2026-01-28 19:12 ` Andrii Nakryiko
2026-01-30 11:31 ` Peter Zijlstra
2026-01-30 20:04 ` Andrii Nakryiko
2026-02-02 19:59 ` Peter Zijlstra
2026-02-04 0:24 ` Andrii Nakryiko
2026-02-04 1:08 ` Andrii Nakryiko
2026-02-05 6:16 ` Tao Chen
2026-02-05 17:34 ` Andrii Nakryiko
2026-02-06 9:20 ` Tao Chen
2026-01-26 7:43 ` [PATCH bpf-next v8 3/3] bpf: Hold ther perf callchain entry until used completely Tao Chen
2026-01-27 21:35 ` Andrii Nakryiko
2026-01-28 4:21 ` Tao Chen
2026-01-28 19:13 ` Andrii Nakryiko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260128091033.GG3372621@noisy.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=acme@kernel.org \
--cc=adrian.hunter@intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=chen.dylane@linux.dev \
--cc=daniel@iogearbox.net \
--cc=eddyz87@gmail.com \
--cc=haoluo@google.com \
--cc=irogers@google.com \
--cc=john.fastabend@gmail.com \
--cc=jolsa@kernel.org \
--cc=kan.liang@linux.intel.com \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=martin.lau@linux.dev \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=sdf@fomichev.me \
--cc=song@kernel.org \
--cc=yonghong.song@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox