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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 Subject: Re: [PATCH] mm/damon/tests/vaddr-kunit: don't use mas_lock for MM_MT_FLAGS-initialized maple tree Date: Wed, 4 Sep 2024 17:19:50 -0700 Message-Id: <20240905001950.1962-1-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <274f253a-e44e-431b-9dd3-a499843be96f@roeck-us.net> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 2620A180004 X-Rspamd-Server: rspam01 X-Stat-Signature: y6awas7zoobzof8zg43xof78ei1hdx15 X-HE-Tag: 1725495594-520131 X-HE-Meta: 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 PzbfOLSo vwy3OY0j8g1yZ9g4VZcUnKf/X0J2vAs3fP2rRABhQYr5uXua5et4ez0JAyYlsGdP2dyOvA1DnjAsL9Dxuns24zCQ8TYmfBrp3+IsRebyokbKqUcKyPlwTHZqn5aG+5UtXHyFWYVBl/J/4uvCf8OpfDuoSM3LUfNAgZdefUEKNSsa38Xqhdzuxq8IEYHfD/udrD5MY9/erI634wSKqOzR7NmwTR+B3A5Wj26+BZkyzgo5LDi2F84pu6vPSoHSyA4pMTVeGp4gXC9LhDlTHaf5HVR+5ADUi8z4p95OS/QigJbWDUuwyO0UsE5ilL3vVellh2Das+QTsI8KvL+SfkAJj+6V7fs9vYFIHhm5tosyXUw65ZmYH8MrfyNE7owXfxrcOySvV0avuBoPUaZc4/NtIgTrNzvj1PZOv4g/GssdtTVcZhw8= 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 Wed, 4 Sep 2024 12:56:33 -0700 Guenter Roeck wrote: > On 9/4/24 12:26, Liam R. Howlett wrote: > > * Guenter Roeck [240904 00:27]: > >> On 9/3/24 20:36, Liam R. 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]: [...] > >>> 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 I was able to reproduce this by further enabling PROVE_LOCKING. > > > > This function isn't taking the rcu read lock while iterating the tree. > > > > Try this: > > > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > > index b0e8b361891d..08cfd22b5249 100644 > > --- a/mm/damon/vaddr.c > > +++ b/mm/damon/vaddr.c > > @@ -126,6 +126,7 @@ static int __damon_va_three_regions(struct mm_struct *mm, > > * If this is too slow, it can be optimised to examine the maple > > * tree gaps. > > */ > > + rcu_read_lock(); > > for_each_vma(vmi, vma) { > > unsigned long gap; > > > > @@ -146,6 +147,7 @@ static int __damon_va_three_regions(struct mm_struct *mm, > > next: > > prev = vma; > > } > > + rcu_read_unlock(); > > > > if (!sz_range(&second_gap) || !sz_range(&first_gap)) > > return -EINVAL; > > > > > Yes, that fixes the problem for me. Thank you for the fix, Liam. Thank you for the test, Guenter. I also confirmed this fix works on my setup. I posted the fix as a formal patch: https://lore.kernel.org/20240905001204.1481-1-sj@kernel.org Thanks, SJ > > Thanks, > Guenter