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From: Qing Wang <wangqing7171@gmail.com>
To: andrii.nakryiko@gmail.com
Cc: acme@kernel.org, andrii@kernel.org, ast@kernel.org,
	bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com,
	haoluo@google.com, john.fastabend@gmail.com, jolsa@kernel.org,
	kpsingh@kernel.org, linux-kernel@vger.kernel.org,
	linux-perf-users@vger.kernel.org, martin.lau@linux.dev,
	peterz@infradead.org, sdf@fomichev.me, song@kernel.org,
	syzbot+72a43cdb78469f7fbad1@syzkaller.appspotmail.com,
	wangqing7171@gmail.com, yonghong.song@linux.dev
Subject: Re: [PATCH] bpf/perf: Fix suspicious RCU usage in get_callchain_entry()
Date: Wed,  4 Feb 2026 17:14:19 +0800	[thread overview]
Message-ID: <20260204091419.887114-1-wangqing7171@gmail.com> (raw)
In-Reply-To: <CAEf4BzYN33yQhO-tsF8pUWDMZoiLAXkV+Z1oP6fJkByocYcjpw@mail.gmail.com>

On Wed, 04 Feb 2026 at 08:04, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> rcu_read_lock/unlock is not called when may_fault == false because in
> that case BPF program is already running within rcu_read_lock/unlock
> region. So I'm not sure this patch fixes anything really. And even
> with trace_in, if we cann rcu_read_lock/unlock one extra time it
> shouldn't be a problem, no?

Thanks for your review, I agree with you. My patch is incorrect and there was a patch series [0]
to fix it.

    [0] https://lore.kernel.org/bpf/fb745675-e25c-4dcc-be4b-4a4411056755@linux.dev/T/#mc0fc5e0fec2e6456f72f402308fd4e397ba19d09

Let's forget my patch.

Thanks,
Qing.

      reply	other threads:[~2026-02-04  9:14 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-28  6:17 [PATCH] bpf/perf: Fix suspicious RCU usage in get_callchain_entry() Qing Wang
2026-02-04  0:04 ` Andrii Nakryiko
2026-02-04  9:14   ` Qing Wang [this message]

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