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Tue, 10 Feb 2026 09:58:56 +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 5REdHmABi2meIAAAD6G6ig (envelope-from ); Tue, 10 Feb 2026 09:58:56 +0000 Message-ID: <7c3549cd-35a9-48cd-b49c-e3a211b8c811@suse.cz> Date: Tue, 10 Feb 2026 10:58:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2 0/2] fix lockdep warnings with kmalloc_nolock() Content-Language: en-US To: Harry Yoo , Andrew Morton Cc: Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Hao Li , linux-mm@kvack.org References: <20260210081900.329447-1-harry.yoo@oracle.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: <20260210081900.329447-1-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 95A17140007 X-Stat-Signature: xnb4kfyq56d963m1px4q7feu7owk4ry4 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1770717539-345370 X-HE-Meta: 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 Q6SK0wel +V4KdB1WR+ckyBG0= 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 2/10/26 09:18, Harry Yoo wrote: > Hi, I've observed two lockdep warnings while testing > kmalloc_nolock() in NMI: > > 1. Accessing current->mems_allowed_seq seqlock in NMI isn't safe > and lockdep complains. > > 2. w/ CONFIG_SLAB_FREELIST_RANDOM, get_random_u32() acquires > a local_lock, which isn't safe in NMI and could cause a deadlock. > > Let's fix them. > > Note: This is based on the latest slab/for-next. It wasn't clear to me > if I should base it on slab/for-next or slab/for-next-fixes, > because the merge window has started, this series needs some exposure > in -next, and the patches in slab/for-next might land in mainline > in the meantime. Right, adding to slab/for-next on top of the submitted PR, so I can send another next week. Thanks! > But the conflict resolution should be trivial even if it should have > been based on slab/for-next-fixes. > > v1 -> v2: > - Patch 1: per Vlastimil's suggestion, do not access > current->mems_allowed_seq and avoid retry if !allow_spin, > rather than returning NULL. > > v1: https://lore.kernel.org/linux-mm/20260206171348.35886-1-harry.yoo@oracle.com > > Harry Yoo (2): > mm/slab: do not access current->mems_allowed_seq if !allow_spin > mm/slab: use prandom if !allow_spin > > mm/slub.c | 41 +++++++++++++++++++++++++++++++++++------ > 1 file changed, 35 insertions(+), 6 deletions(-) > > > base-commit: f6ed7e47c1fc78e78c9bfeb668b1ad9ba5c58120 >