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Fri, 6 Feb 2026 17:34:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2/slESImhmnNcAAAD6G6ig (envelope-from ); Fri, 06 Feb 2026 17:34:26 +0000 Message-ID: <651bd1f9-8971-48da-a0c4-328e235c2eab@suse.cz> Date: Fri, 6 Feb 2026 18:34:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: skip debug_check_no_{obj,locks}_freed with FPI_TRYLOCK Content-Language: en-US To: Harry Yoo , Zi Yan Cc: Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Alexei Starovoitov , Sebastian Andrzej Siewior , Shakeel Butt , linux-mm@kvack.org, stable@vger.kernel.org References: <20260206165802.17280-1-harry.yoo@oracle.com> <7B9B9CF3-29A6-4271-8C3C-87FF3EB9FA4D@nvidia.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Stat-Signature: pcw6brz1eqob9eqys1a1x5hazwihh3ig X-Rspam-User: X-Rspamd-Queue-Id: 4C62B8000B X-HE-Tag: 1770399268-546474 X-HE-Meta: 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 ugcnyDZO Bsr9ygnDrALiKKVlL+d1y9mIsJ1bOGGda5bHtePBAzqgvynpmlbxbh2xf0s2RI9HHwKKtxnfrHwzZ0cZ359B0/XgUZqf3HJgoon7QWwxGA4TKHGCV5UueNcMxmD9XpCqUAZOcI1n4UlKJ9GR+rYo/ldpDKViP+d9s4sL2YNejHkLIQ3KfqvkvK7iXfGl2pKizRtxApPiEwABnfSrtHVRW0v5B4OQZ9dOoaM3GdS6SnFkgym5Fr1/jpefXGfhl2I1gQAo77Y34WMHtI1XkIvJfIKx2DO+OcPBgmUqJan2O9WPfMptTyl6j7+4AT7eQAzycFsw4nb+NfI0qRnKiCRnqOQo4Ud9te1vZoMWmRhwf4/x3pSMNSF8QSAcSrxFBuTbhNzu7 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 2/6/26 18:20, Harry Yoo wrote: > On Fri, Feb 06, 2026 at 12:08:04PM -0500, Zi Yan wrote: >> On 6 Feb 2026, at 11:58, Harry Yoo wrote: >> >> > When CONFIG_DEBUG_OBJECTS_FREE is enabled, >> > debug_check_no_{obj,locks}_freed() functions are called. >> > >> > Since both of them spin on a lock, they are not safe to be called >> > if the FPI_TRYLOCK flag is specified. This leads to a lockdep splat: >> > >> > ================================ >> > WARNING: inconsistent lock state >> > 6.19.0-rc5-slab-for-next+ #326 Tainted: G N >> > -------------------------------- >> > inconsistent {INITIAL USE} -> {IN-NMI} usage. >> > kunit_try_catch/9046 [HC2[2]:SC0[0]:HE0:SE1] takes: >> > ffffffff84ed6bf8 (&obj_hash[i].lock){-.-.}-{2:2}, at: __debug_check_no_obj_freed+0xe0/0x300 >> > {INITIAL USE} state was registered at: >> > lock_acquire+0xd9/0x2f0 >> > _raw_spin_lock_irqsave+0x4c/0x80 >> > __debug_object_init+0x9d/0x1f0 >> > debug_object_init+0x34/0x50 >> > __init_work+0x28/0x40 >> > init_cgroup_housekeeping+0x151/0x210 >> > init_cgroup_root+0x3d/0x140 >> > cgroup_init_early+0x30/0x240 >> > start_kernel+0x3e/0xcd0 >> > x86_64_start_reservations+0x18/0x30 >> > x86_64_start_kernel+0xf3/0x140 >> > common_startup_64+0x13e/0x148 >> > irq event stamp: 2998 >> > hardirqs last enabled at (2997): [] exc_nmi+0x11a/0x240 >> > hardirqs last disabled at (2998): [] sysvec_irq_work+0x11/0x110 >> > softirqs last enabled at (1416): [] __irq_exit_rcu+0x132/0x1c0 >> > softirqs last disabled at (1303): [] __irq_exit_rcu+0x132/0x1c0 >> > >> > other info that might help us debug this: >> > Possible unsafe locking scenario: >> > >> > CPU0 >> > ---- >> > lock(&obj_hash[i].lock); >> > >> > lock(&obj_hash[i].lock); >> > >> > *** DEADLOCK *** >> > >> > Fix this by adding an fpi_t parameter to free_pages_prepare() and >> > skipping those checks if FPI_TRYLOCK is set. Since mm/compaction.c >> > calls free_pages_prepare(), move the fpi_t definition to mm/internal.h. >> > >> > Fixes: 8c57b687e833 ("mm, bpf: Introduce free_pages_nolock()") >> > Cc: >> > Signed-off-by: Harry Yoo >> > --- >> > mm/compaction.c | 2 +- >> > mm/internal.h | 35 ++++++++++++++++++++++++++++++++++- >> > mm/page_alloc.c | 42 ++++++------------------------------------ >> > 3 files changed, 41 insertions(+), 38 deletions(-) >> > >> > diff --git a/mm/compaction.c b/mm/compaction.c >> > index 1e8f8eca318c..9ffeb7c6d2b0 100644 >> > --- a/mm/compaction.c >> > +++ b/mm/compaction.c >> > @@ -1859,7 +1859,7 @@ static void compaction_free(struct folio *dst, unsigned long data) >> > struct page *page = &dst->page; >> > >> > if (folio_put_testzero(dst)) { >> > - free_pages_prepare(page, order); >> > + free_pages_prepare(page, order, FPI_NONE); >> >> Is it OK to add something like free_pages_prepare_fpi_none() for this one >> to avoid the FPI flag move? > > Yeah, moving FPI flag definition isn't great :) > > I'm totally fine with your suggestion, > as long as page allocator/compaction folks are fine with it! Maybe even like this? free_pages_prepare() which calls __free_pages_prepare(FPI_NONE)