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d=hostedemail.com; t=1760320317; a=rsa-sha256; cv=none; b=27VU941JNSBoqiohlVH1LQDtfOF0DTl0MISr+1ySKpKdzAlOOkWYM2NLnF/lOYyAHIn8TE cF1T+WRI7ZMogrNZc71FjsIV0AarmmWWf2yLf0plUFkEkOac/sV3vvLS9bE3ObM9EHSR9T JLYL9sKp0E/VZ3Oiwu2aWUWvpAZsXZI= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf12.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-c45ff70000001609-f8-68ec5b3b579e Date: Mon, 13 Oct 2025 10:51:49 +0900 From: Byungchul Park To: Mark Brown Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com, torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, will@kernel.org, tglx@linutronix.de, rostedt@goodmis.org, joel@joelfernandes.org, sashal@kernel.org, daniel.vetter@ffwll.ch, duyuyang@gmail.com, johannes.berg@intel.com, tj@kernel.org, tytso@mit.edu, willy@infradead.org, david@fromorbit.com, amir73il@gmail.com, gregkh@linuxfoundation.org, kernel-team@lge.com, linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, sj@kernel.org, jglisse@redhat.com, dennis@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, vbabka@suse.cz, ngupta@vflare.org, linux-block@vger.kernel.org, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, jlayton@kernel.org, dan.j.williams@intel.com, hch@infradead.org, djwong@kernel.org, dri-devel@lists.freedesktop.org, rodrigosiqueiramelo@gmail.com, melissa.srw@gmail.com, hamohammed.sa@gmail.com, harry.yoo@oracle.com, chris.p.wilson@intel.com, gwan-gyeong.mun@intel.com, max.byungchul.park@gmail.com, boqun.feng@gmail.com, longman@redhat.com, yunseong.kim@ericsson.com, ysk@kzalloc.com, yeoreum.yun@arm.com, netdev@vger.kernel.org, matthew.brost@intel.com, her0gyugyu@gmail.com, corbet@lwn.net, catalin.marinas@arm.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, sumit.semwal@linaro.org, gustavo@padovan.org, christian.koenig@amd.com, andi.shyti@kernel.org, arnd@arndb.de, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org, samitolvanen@google.com, paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, chuck.lever@oracle.com, neil@brown.name, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, trondmy@kernel.org, anna@kernel.org, kees@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, mark.rutland@arm.com, ada.coupriediaz@arm.com, kristina.martsenko@arm.com, wangkefeng.wang@huawei.com, kevin.brodsky@arm.com, dwmw@amazon.co.uk, shakeel.butt@linux.dev, ast@kernel.org, ziy@nvidia.com, yuzhao@google.com, baolin.wang@linux.alibaba.com, usamaarif642@gmail.com, joel.granados@kernel.org, richard.weiyang@gmail.com, geert+renesas@glider.be, tim.c.chen@linux.intel.com, linux@treblig.org, alexander.shishkin@linux.intel.com, lillian@star-ark.net, chenhuacai@kernel.org, francesco@valla.it, guoweikang.kernel@gmail.com, link@vivo.com, jpoimboe@kernel.org, masahiroy@kernel.org, brauner@kernel.org, thomas.weissschuh@linutronix.de, oleg@redhat.com, mjguzik@gmail.com, andrii@kernel.org, wangfushuai@baidu.com, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-i2c@vger.kernel.org, linux-arch@vger.kernel.org, linux-modules@vger.kernel.org, rcu@vger.kernel.org, linux-nfs@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH v17 09/47] arm64, dept: add support CONFIG_ARCH_HAS_DEPT_SUPPORT to arm64 Message-ID: <20251013015149.GC52546@system.software.com> References: <20251002081247.51255-1-byungchul@sk.com> <20251002081247.51255-10-byungchul@sk.com> <20251003014641.GF75385@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; 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Can you explain > > in more detail with example? > > Your commit log says we need to track every entrance from user mode to > kernel mode but the code only adds tracking to syscalls and some memory > faults. The exception types listed above (and some others) also result > in entries to the kernel from userspace. You're right. Each kernel mode context needs to be tracked independently. Just for your information, context ID is used for making DEPT only track waits and events within each context, preventing tracking those across independent contexts to avoid false positives. Currently, irq, fault, and system calls are covered. It should be taken into account if any other exceptions can include waits and events anyway. > > JFYI, pairs of wait and its event need to be tracked to see if each > > event can be prevented from being reachable by other waits like: > > > context X context Y > > > > lock L > > ... > > initiate event A context start toward event A > > ... ... > > wait A // wait for event A and lock L // wait for unlock L and > > // prevent unlock L // prevent event A > > ... ... > > unlock L unlock L > > ... > > event A > > > I meant things like this need to be tracked. > > I don't think that's at all clear from the above context, and the > handling for some of the above exception types (eg, the vector > extensions) includes taking locks. A trivial thing to mention, each typical lock pair, lock and unlock, can only happen within each independent context, not across different contexts. So the context ID is not necessary for typical locks. exception X lock A; ... unlock A; // already guarateed to unlock A in the context that lock A // has been acqured in. ... finish exception X and return back to user mode; But yes, as you concern, we should take into account all the exceptions if any can include general waits and events in it, to avoid unnecessary false positives. Thank you! Byungchul