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Mon, 22 Dec 2025 00:01:35 -0800 (PST) From: liujing40 X-Google-Original-From: liujing40 To: rostedt@goodmis.org Cc: alexei.starovoitov@gmail.com, 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-trace-kernel@vger.kernel.org, liujing.root@gmail.com, liujing40@xiaomi.com, martin.lau@linux.dev, mhiramat@kernel.org, sdf@fomichev.me, song@kernel.org, yonghong.song@linux.dev Subject: Re: [PATCH 2/2] bpf: Implement kretprobe fallback for kprobe multi link Date: Mon, 22 Dec 2025 16:00:46 +0800 Message-Id: <20251222080046.2312024-1-liujing40@xiaomi.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20251218160925.3c02a721@gandalf.local.home> References: <20251218160925.3c02a721@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Thu, 18 Dec 2025 16:09:25 -0500 Steven Rostedt wrote: > On Thu, 18 Dec 2025 09:53:16 -0800 > Alexei Starovoitov wrote: > > > > +static void bpf_kprobe_unregister(struct bpf_kprobe *kps, u32 cnt) > > > +{ > > > + for (int i = 0; i < cnt; i++) > > > + unregister_kretprobe(&kps[i].rp); > > > +} > > > > Nack. > > This is not a good idea. > > unregister_kretprobe() calls synchronize_rcu(). > > So the above loop will cause soft lockups for sure. > > Looks like it could be replaced with: > > unregister_kretprobes(kps, cnt); > > Which unregisters an array of kreptrobes and does a single > synchronize_rcu(). > > -- Steve Thanks for the suggestion. I will refactor the loop to use unregister_kretprobes() for a single RCU sync.