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Howlett" , Peng Zhang , kernel test robot , oe-lkp@lists.linux.dev, lkp@intel.com, maple-tree@lists.infradead.org, linux-mm@kvack.org, corbet@lwn.net, akpm@linux-foundation.org, brauner@kernel.org, surenb@google.com, michael.christie@oracle.com, peterz@infradead.org, mathieu.desnoyers@efficios.com, npiggin@gmail.com, avagin@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2 5/6] maple_tree: Update check_forking() and bench_forking() Message-ID: References: <202308312115.cad34fed-oliver.sang@intel.com> <0e9a87d9-410f-a906-e95c-976a141f24f0@bytedance.com> <20230907180301.lms4ihtwfuwj7bkb@revolver> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230907180301.lms4ihtwfuwj7bkb@revolver> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A5B5540018 X-Stat-Signature: 6b5qcbi9jz3cowcsf8qhokhjbohswpfr X-Rspam-User: X-HE-Tag: 1694110618-905929 X-HE-Meta: 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 FYgIXApe xXQckqD65NJKRfw6TADC5arYCCE3//XWX8g/Cq3falOWezaojRmQ208571zx1cCXG67TDyt+ToK9CH9jHqPiHA77bpzpswtSDLzJJOMyOe9aeCBeQpvS42JF/URZm1OJbJSOErpJToETLLLg8ee2RZUMCrJKABS6N0OY4qx1SBgR7WMeWzBQZQQxSQQ== 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: On Thu, Sep 07, 2023 at 02:03:01PM -0400, Liam R. Howlett wrote: > > > WARNING: possible recursive locking detected > > > 6.5.0-rc4-00632-g2730245bd6b1 #1 Tainted: G TN > > > -------------------------------------------- > > > swapper/1 is trying to acquire lock: > > > ffffffff86485058 (&mt->ma_lock){+.+.}-{2:2}, at: check_forking (include/linux/spinlock.h:? lib/test_maple_tree.c:1854) > > > > > > but task is already holding lock: > > > ffff888110847a30 (&mt->ma_lock){+.+.}-{2:2}, at: check_forking (include/linux/spinlock.h:351 lib/test_maple_tree.c:1854) > > Thanks for the test. I checked that these are two different locks, why > > is this warning reported? Did I miss something? > > I don't think you can nest spinlocks like this. In my previous test I > avoided nesting, but in your case we cannot avoid having both locks at > the same time. > > You can get around this by using an rwsemaphore, set the two trees as > external and use down_write_nested(&lock2, SINGLE_DEPTH_NESTING) like > the real fork. Basically, switch the locking to exactly what fork does. spin_lock_nested() exists. You should probably both read through Documentation/locking/lockdep-design.rst It's not the best user documentation in the world, but it's what we have.