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Thu, 04 Sep 2025 03:46:33 -0700 (PDT) Received: from krava ([2a02:8308:a00c:e200::31e0]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b017e4b9ed7sm1308898266b.90.2025.09.04.03.46.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Sep 2025 03:46:32 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 4 Sep 2025 12:46:31 +0200 To: Oleg Nesterov Cc: Jiri Olsa , Masami Hiramatsu , Peter Zijlstra , Andrii Nakryiko , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Ingo Molnar Subject: Re: [PATCH perf/core 02/11] uprobes: Skip emulate/sstep on unique uprobe when ip is changed Message-ID: References: <20250902143504.1224726-1-jolsa@kernel.org> <20250902143504.1224726-3-jolsa@kernel.org> <20250903112648.GC18799@redhat.com> <20250904084949.GB27255@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250904084949.GB27255@redhat.com> On Thu, Sep 04, 2025 at 10:49:50AM +0200, Oleg Nesterov wrote: > On 09/03, Jiri Olsa wrote: > > > > On Wed, Sep 03, 2025 at 01:26:48PM +0200, Oleg Nesterov wrote: > > > On 09/02, Jiri Olsa wrote: > > > > > > > > If user decided to take execution elsewhere, it makes little sense > > > > to execute the original instruction, so let's skip it. > > > > > > Exactly. > > > > > > So why do we need all these "is_unique" complications? Only a single > > > is_unique/exclusive consumer can change regs->ip, so I guess handle_swbp() > > > can just do > > > > > > handler_chain(uprobe, regs); > > > if (instruction_pointer(regs) != bp_vaddr) > > > goto out; > > > > hum, that's what I did in rfc [1] but I thought you did not like that [2] > > > > [1] https://lore.kernel.org/bpf/20250801210238.2207429-2-jolsa@kernel.org/ > > [2] https://lore.kernel.org/bpf/20250802103426.GC31711@redhat.com/ > > > > I guess I misunderstood your reply [2], I'd be happy to drop the > > unique/exclusive flag > > Well, but that rfc didn't introduce the exclusive consumers, and I think > we agree that even with these changes the non-exclusive consumers must > never change regs->ip? ok, got excited too soon.. so you meant getting rid of is_unique check only for this patch and have just change below.. but keep the unique/exclusive flag from patch#1 IIUC Andrii would remove the unique flag completely? jirka -- diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index b9b088f7333a..1baf5d2792ff 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2791,6 +2791,9 @@ static void handle_swbp(struct pt_regs *regs) handler_chain(uprobe, regs); + if (instruction_pointer(regs) != bp_vaddr) + goto out; + /* Try to optimize after first hit. */ arch_uprobe_optimize(&uprobe->arch, bp_vaddr);