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imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706502062; a=rsa-sha256; cv=none; b=f5q7ixPnFsNBZ1InyeOC0pwhDsEL82wg/kdzN78Mpv7IvjCbrnT5zRc+p730TQJHuswI7g wen8yW+1Gpt5imLphyzq18hHdP0SQD7OWiXL6CEM9UDovED6+C2V6+/PEvSZADWYRSzkZy 8D/s5cnf7UxsiJ7J5RAnQGMGaKBpEjQ= X-AuditID: a67dfc5b-d6dff70000001748-0b-65b727aa4de6 Date: Mon, 29 Jan 2024 13:20:52 +0900 From: Byungchul Park To: Thomas Gleixner 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, 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, viro@zeniv.linux.org.uk, 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, 42.hyeyoo@gmail.com, chris.p.wilson@intel.com, gwan-gyeong.mun@intel.com, max.byungchul.park@gmail.com, boqun.feng@gmail.com, longman@redhat.com, hdanton@sina.com, her0gyugyu@gmail.com Subject: Re: [PATCH v11 14/26] locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread Message-ID: <20240129042052.GA64402@system.software.com> References: <20240124115938.80132-1-byungchul@sk.com> <20240124115938.80132-15-byungchul@sk.com> <87il3ggfz9.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; 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You are changing the CPU > hotplug (not hotplus) code, right? I will fix the typo ;( Thank you. I referred to the commit cb92173d1f047. I will remove the prefix if the way is more desirable. > > cb92173d1f0 ("locking/lockdep, cpu/hotplug: Annotate AP thread") was > > introduced to make lockdep_assert_cpus_held() work in AP thread. > > > > However, the annotation is too strong for that purpose. We don't have to > > use more than try lock annotation for that. > > This lacks a proper explanation why this is too strong. rwsem_acquire() implies: 1. might be a waiter on contention of the lock. 2. enter to the critical section of the lock. All we need in here is to act 2, not 1. That's why I suggested trylock version of annotation for that purpose. Now that dept partially replies on lockdep annotaions for the waiters and events, dept is interpeting rwsem_acquire() as a potential waiter and reports a deadlock by the wait. Of course, the first priority should be not to change the current behavior. I think the change from non-trylock to trylock for the annotation won't. Or am I missing something? Byungchul > > Furthermore, now that Dept was introduced, false positive alarms was > > reported by that. Replaced it with try lock annotation. > > I still have zero idea what this is about. > > Thanks, > > tglx