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([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-206ae912facsm5545075ad.45.2024.09.03.21.27.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Sep 2024 21:27:24 -0700 (PDT) Message-ID: Date: Tue, 3 Sep 2024 21:27:22 -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: "Liam R. Howlett" , SeongJae Park , 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: <20240904005815.1388-1-sj@kernel.org> <20240904011840.973-1-sj@kernel.org> <54zu64vxrhdxr4wtmwbewga44shu4f7lz4ffx2hxhag46b56hn@qgrgfrb6mhbv> 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: <54zu64vxrhdxr4wtmwbewga44shu4f7lz4ffx2hxhag46b56hn@qgrgfrb6mhbv> Content-Type: text/plain; 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Howlett wrote: > * Guenter Roeck [240903 22:38]: >> On 9/3/24 19:31, Liam R. Howlett wrote: >>> * SeongJae Park [240903 21:18]: >>>> 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? >>> >>> That would be the lockdep complaining, so that's good. >>> >>>> >>>> I was actually thinking replacing the mt_init_flags() with mt_init(), which >>>> same to mt_init_flags() with zero flag, like below. >>> >>> Yes. This will use the spinlock which should fix your issue, but it >>> will use a different style of maple tree. >>> >>> Perhaps use MT_FLAGS_ALLOC_RANGE to use the same type of maple tree, if >>> you ever add threading you will want the rcu flag as well >>> (MT_FLAGS_USE_RCU). >>> >>> I would recommend those two and just use the spinlock. >>> >> >> I tried that (MT_FLAGS_ALLOC_RANGE | MT_FLAGS_USE_RCU). it also triggers >> the suspicious RCU usage message. >> > > I am running ./tools/testing/kunit/kunit.py run '*damon*' --arch x86_64 --raw > with: > CONFIG_LOCKDEP=y > CONFIG_DEBUG_SPINLOCK=y > > and I don't have any issue with locking in the existing code. How do I > recreate this issue? > I tested again, and I still see [ 6.233483] ok 4 damon [ 6.234190] KTAP version 1 [ 6.234263] # Subtest: damon-operations [ 6.234335] # module: vaddr [ 6.234384] 1..6 [ 6.235726] [ 6.235931] ============================= [ 6.236018] WARNING: suspicious RCU usage [ 6.236280] 6.11.0-rc6-00029-gda66250b210f-dirty #1 Tainted: G N [ 6.236398] ----------------------------- [ 6.236474] lib/maple_tree.c:832 suspicious rcu_dereference_check() usage! [ 6.236579] [ 6.236579] other info that might help us debug this: [ 6.236579] [ 6.236738] [ 6.236738] rcu_scheduler_active = 2, debug_locks = 1 [ 6.237039] no locks held by kunit_try_catch/208. [ 6.237166] [ 6.237166] stack backtrace: [ 6.237385] CPU: 0 UID: 0 PID: 208 Comm: kunit_try_catch Tainted: G N 6.11.0-rc6-00029-gda66250b210f-dirty #1 [ 6.237629] Tainted: [N]=TEST [ 6.237714] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 6.238065] Call Trace: [ 6.238233] [ 6.238547] dump_stack_lvl+0x9e/0xe0 [ 6.239473] lockdep_rcu_suspicious+0x145/0x1b0 [ 6.239621] mas_walk+0x19f/0x1d0 [ 6.239765] mas_find+0xb5/0x150 [ 6.239873] __damon_va_three_regions+0x7e/0x130 [ 6.240039] damon_test_three_regions_in_vmas+0x1ea/0x480 [ 6.240551] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [ 6.240712] kunit_try_run_case+0x93/0x190 [ 6.240850] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [ 6.240990] kunit_generic_run_threadfn_adapter+0x1c/0x40 [ 6.241124] kthread+0xdd/0x110 [ 6.241256] ? __pfx_kthread+0x10/0x10 [ 6.241368] ret_from_fork+0x2f/0x50 [ 6.241468] ? __pfx_kthread+0x10/0x10 [ 6.241573] ret_from_fork_asm+0x1a/0x30 [ 6.241765] [ 6.242180] [ 6.242270] ============================= [ 6.242375] WARNING: suspicious RCU usage [ 6.242478] 6.11.0-rc6-00029-gda66250b210f-dirty #1 Tainted: G N [ 6.242634] ----------------------------- [ 6.242734] lib/maple_tree.c:788 suspicious rcu_dereference_check() usage! [ 6.242955] [ 6.242955] other info that might help us debug this: [ 6.242955] [ 6.243098] [ 6.243098] rcu_scheduler_active = 2, debug_locks = 1 [ 6.243215] no locks held by kunit_try_catch/208. [ 6.243331] [ 6.243331] stack backtrace: [ 6.243420] CPU: 0 UID: 0 PID: 208 Comm: kunit_try_catch Tainted: G N 6.11.0-rc6-00029-gda66250b210f-dirty #1 [ 6.243599] Tainted: [N]=TEST [ 6.243665] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 6.243844] Call Trace: [ 6.243907] [ 6.243961] dump_stack_lvl+0x9e/0xe0 [ 6.244032] lockdep_rcu_suspicious+0x145/0x1b0 [ 6.244121] mtree_range_walk+0x2b9/0x350 [ 6.244211] mas_walk+0x107/0x1d0 [ 6.244278] mas_find+0xb5/0x150 [ 6.244341] __damon_va_three_regions+0x7e/0x130 [ 6.244445] damon_test_three_regions_in_vmas+0x1ea/0x480 [ 6.244770] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [ 6.244865] kunit_try_run_case+0x93/0x190 [ 6.244952] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [ 6.245044] kunit_generic_run_threadfn_adapter+0x1c/0x40 [ 6.245130] kthread+0xdd/0x110 [ 6.245191] ? __pfx_kthread+0x10/0x10 [ 6.245262] ret_from_fork+0x2f/0x50 [ 6.245326] ? __pfx_kthread+0x10/0x10 [ 6.245394] ret_from_fork_asm+0x1a/0x30 [ 6.245497] [ 6.246605] # damon_test_three_regions_in_vmas: pass:1 fail:0 skip:0 total:1 [ 6.246668] ok 1 damon_test_three_regions_in_vmas This is with diff --git a/mm/damon/vaddr-test.h b/mm/damon/vaddr-test.h index 83626483f82b..a339d117150f 100644 --- a/mm/damon/vaddr-test.h +++ b/mm/damon/vaddr-test.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_flags(&mm.mm_mt, MT_FLAGS_ALLOC_RANGE | MT_FLAGS_USE_RCU); if (__link_vmas(&mm.mm_mt, vmas, ARRAY_SIZE(vmas))) kunit_skip(test, "Failed to create VMA tree"); I'll put it all together and make it available, but that will have to wait until tomorrow. Thanks, Guenter