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([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-206aea684bdsm4118095ad.254.2024.09.03.18.54.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Sep 2024 18:54:30 -0700 (PDT) Message-ID: Date: Tue, 3 Sep 2024 18:54:28 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/damon/tests/vaddr-kunit: don't use mas_lock for MM_MT_FLAGS-initialized maple tree To: SeongJae Park Cc: "Liam R. Howlett" , Andrew Morton , "Matthew Wilcox (Oracle)" , David Hildenbrand , Brendan Higgins , David Gow , damon@lists.linux.dev, linux-mm@kvack.org, kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240904011840.973-1-sj@kernel.org> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= In-Reply-To: <20240904011840.973-1-sj@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: osgrpha7tzykh59hy53udzmf6sb18o8n X-Rspamd-Queue-Id: B63AB40006 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1725414872-95991 X-HE-Meta: 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 3TWXpp6F 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 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 9/3/24 18:18, SeongJae Park wrote: > On Tue, 3 Sep 2024 17:58:15 -0700 SeongJae Park wrote: > >> On Tue, 3 Sep 2024 20:48:53 -0400 "Liam R. Howlett" wrote: >> >>> * SeongJae Park [240903 20:45]: >>>> damon_test_three_regions_in_vmas() initializes a maple tree with >>>> MM_MT_FLAGS. The flags contains MT_FLAGS_LOCK_EXTERN, which means >>>> mt_lock of the maple tree will not be used. And therefore the maple >>>> tree initialization code skips initialization of the mt_lock. However, >>>> __link_vmas(), which adds vmas for test to the maple tree, uses the >>>> mt_lock. In other words, the uninitialized spinlock is used. The >>>> problem becomes celar when spinlock debugging is turned on, since it >>>> reports spinlock bad magic bug. Fix the issue by not using the mt_lock >>>> as promised. >>> >>> You can't do this, lockdep will tell you this is wrong. >> >> Hmm, but lockdep was silence on my setup? >> >>> We need a lock and to use the lock for writes. >> >> This code is executed by a single-thread test code. Do we still need the lock? >> >>> >>> I'd suggest using different flags so the spinlock is used. >> >> The reporter mentioned simply dropping MT_FLAGS_LOCK_EXTERN from the flags >> causes suspicious RCU usage message. May I ask if you have a suggestion of >> better flags? > > I was actually thinking replacing the mt_init_flags() with mt_init(), which > same to mt_init_flags() with zero flag, like below. > > ``` > --- a/mm/damon/tests/vaddr-kunit.h > +++ b/mm/damon/tests/vaddr-kunit.h > @@ -77,7 +77,7 @@ static void damon_test_three_regions_in_vmas(struct kunit *test) > (struct vm_area_struct) {.vm_start = 307, .vm_end = 330}, > }; > > - mt_init_flags(&mm.mm_mt, MM_MT_FLAGS); > + mt_init(&mm.mm_mt); > if (__link_vmas(&mm.mm_mt, vmas, ARRAY_SIZE(vmas))) > kunit_skip(test, "Failed to create VMA tree"); > ``` > > And just confirmed it also convinces the reproducer. But because I'm obviously > not familiar with maple tree, would like to hear some comments from Liam or > others first. > Same here. That is why I gave up after trying MT_FLAGS_ALLOC_RANGE and "MT_FLAGS_ALLOC_RANGE | MT_FLAGS_USE_RCU". After all, I really don't know what I am doing and was just playing around ... and there isn't really a good explanation why initializing the maple tree with MT_FLAGS_ALLOC_RANGE (but not MT_FLAGS_USE_RCU) would trigger rcu warnings. Guenter