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Wed, 04 Feb 2026 01:14:27 -0800 (PST) From: Qing Wang 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 Message-Id: <20260204091419.887114-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Wed, 04 Feb 2026 at 08:04, Andrii Nakryiko 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.