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Wed, 10 Sep 2025 02:54:45 -0700 (PDT) Message-ID: Date: Wed, 10 Sep 2025 17:54:33 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/18] x86/hw_breakpoint: introduce arch_reinstall_hw_breakpoint() for atomic context From: Jinchao Wang To: "Masami Hiramatsu (Google)" Cc: Peter Zijlstra , Andrew Morton , "Naveen N . Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-perf-users@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250904002126.1514566-1-wangjinchao600@gmail.com> <20250904002126.1514566-6-wangjinchao600@gmail.com> <20250904063832.GT4067720@noisy.programming.kicks-ass.net> <20250909170017.dae27d8be77f9ec634e0d56c@kernel.org> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 24BFD20008 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: be7eeoj5oteb6k8x9ayb4tt6s4w533q9 X-HE-Tag: 1757498086-763478 X-HE-Meta: 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 yq/Vlbg7 gB1Zjfzv8jx+7usuAuCFugF+P7i4ZtHWQsMXGtkVtNL5ZPlxmG2E64fx6GoMoatCxd7WXpY/plAtT2Azx9193lsGunV0W3VKXRT+CNITi6+uPOerTXN+m++loYsq+ACN3KZsZw568nWIguiwocGUTw+W38g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/9/25 16:39, Jinchao Wang wrote: > > On 9/9/25 16:00, Masami Hiramatsu (Google) wrote: >> On Mon, 8 Sep 2025 13:20:51 +0800 >> Jinchao Wang wrote: >>>> ... >>>> >>>> Yeah, I think not. For one this is an almost verbatim copy of >>>> arch_install_hw_breakpoint() with zero re-use. Surely you've been >>>> taught >>>> better? >>> I introduced this to modify bp_addr in atomic context in my RFC series. >>> I thought it was clearer to split the introduction and refactor. >>> And then It was used in the wprobe series, so I left it as introduced >>> in the RFC series. >>> >>> I agree your suggestion is right. I am willing to refactor after >>> wprobe. >> I'm OK to refactor it to reuse arch_install_hw_breakpoint(). >> My point is to have CONFIG_HAVE_REINSTALL_HW_BREAKPOINT so that >> we can easily implement the dependency for other features which >> requires this feature in Kconfig level. >> >>>> And why would we want to export guts like this? >>> I wanted to introduce a real-time stack corruption debugging tool, >>> which needs a helper to change bp_addr in atomic context (kprobe >>> handler). >>> And wprobe needs it also. >> I agree with Peter, it should not expose the architecture >> dependent code directly. Instead, we need a wrapper. >> >> Thank you, > Understood, I will use the wrapper instead. > > Hi Masami, I would like to ask for your advice regarding a development workflow issue. I have a patch series that refactors |arch_reinstall_hw_breakpoint|, which I know you are using in your |wprobe| series. My new feature, |kstackwatch|, is dependent on my patches and also on your wrapper patch for |modify_wide_hw_breakpoint_local|. Since we are working on different subsystems with different maintainers, I am concerned about how to handle the dependencies between our patches to avoid introducing trouble. What is the best practice for this type of cross-subsystem dependency? Should one of us carry all the patches until they are merged, or is there a standard procedure for this situation? Thank you for your guidance. -- Thanks, Jinchao