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Fri, 08 Sep 2023 02:47:15 -0700 (PDT) Received: from [10.254.232.87] ([139.177.225.246]) by smtp.gmail.com with ESMTPSA id p5-20020a170902bd0500b001bba7aab822sm439696pls.5.2023.09.08.02.47.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Sep 2023 02:47:14 -0700 (PDT) Message-ID: Date: Fri, 8 Sep 2023 17:47:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH v2 5/6] maple_tree: Update check_forking() and bench_forking() To: Matthew Wilcox , "Liam R. 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 References: <202308312115.cad34fed-oliver.sang@intel.com> <0e9a87d9-410f-a906-e95c-976a141f24f0@bytedance.com> <20230907180301.lms4ihtwfuwj7bkb@revolver> From: Peng Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 582A020011 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: uaat3qqtj8brphd5mcp5xqs3e9qh9grp X-HE-Tag: 1694166436-511380 X-HE-Meta: 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 tHLR0Oa6 XOw/1ODXcwosYcwZycO3hiG7ZKUO20q2aHDvIKUp9a9UBKk7ZYjlUwEFPSUKYLoq+4OJDiSIMdGCw1ibPoVCLP8xrIzHSLpd7uMH2pPMwsDFsYYvD3rZ0pdW8mPZPoSRtO/DbfhCiH1H4romouYvctMzNQ4rsC+QDzIyJKH+KuYy0tkEYdRwi3LYOvuMUOhPDaZe5KsWoUuyQiognXA2OmXY6jt3z+8kpMnXjUDvIDV6DEiZDME8ZRoe/SZzxgqA/fE3eRT8XpF6o3i/Lr2B/WJ62ed7PjqLcLBSWLVx6S2xtLj0lG+hI0sUdFTFOOX6ZA6Yg5bcahkaOhX2CMsN1dV+u+o/cPaJXF0DRJtG9XDW/JCebJB2uQgmCNaXCJ0/U/ZmynSG4tdV5MWdBBO4sRRGRbWLEqQ3wR9Nn 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: 在 2023/9/8 02:16, Matthew Wilcox 写道: > 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. Here I can use rwsemaphore to avoid the warning. But what about in mtree_dup()? mtree_dup() handles locks internally. Maybe spin_lock_nested() mentioned by Matthew can be used in mtree_dup(). > > spin_lock_nested() exists. Thanks for mentioning this, I'll have a look. > > 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. >