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Fri, 3 Oct 2025 06:52:29 +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 11QUFq1y32h0VQAAD6G6ig (envelope-from ); Fri, 03 Oct 2025 06:52:29 +0000 Message-ID: Date: Fri, 3 Oct 2025 08:52:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: Fix using this_cpu_ptr() in preemptible context To: Harry Yoo Cc: Alexei Starovoitov , ranxiaokai627@163.com, Andrew Morton , cl@gentwo.org, David Rientjes , Roman Gushchin , Alexei Starovoitov , LKML , linux-mm , ran.xiaokai@zte.com.cn References: <20250930083402.782927-1-ranxiaokai627@163.com> Content-Language: en-US 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-Action: no action X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3275E40002 X-Stat-Signature: py9pcz7a7k9y6ohmjiq8dus8oe8scs5w X-HE-Tag: 1759474351-291066 X-HE-Meta: U2FsdGVkX19vpmT/JVFxfZavWma4G9X2cviieo7G3haLjrgS4L3GZdcQnIcJ0x0ZT2ZVn6hzYhm9KWsWuXgK7b52w77EB/cV7cEp/UqDvg1Q//2gd/I2Y/XZ96a2bKQqC2/FyxJuWeCd4+t6b5PQnj1xiudjaI0ElfraUrUSi11l8Tlv13wuetvOaZTanzoELYFD6Cm+eEBTU/JR94gMe9sHgTOLU1REJjHqeGb6gPxiWTyog+l8MW5PSHHjPZJZwPGvGr53uJz5nP1mm6llO9r8MdKZ6srKKvlNlt6Yw49nSMMuqfjKWHPY3apVa0N7JLf4B7nQ9oemWSGn4Avjth5WlZUFdm3xKpWmZFha2SEJU1Xf2F6LoTYxsQKPSOfg7S+ejXwyDwLQ3NCr0wwH4JeqA6pWyQZ7JAgwrnv94K7YnoR8If64H4ucxrxdMjJLPmU1KoSaE/8yrQ5/cAjCno/J1OSXlIlSghti/3C+H5f2rtGci7+z+wxsmdRyewMkb79b3dvc4mqAFKBbuzynHS6ixqhqKs05fM6bCgPln8VxSay/gAihrL6GxjZIE8/9mh3Q1c/MlDqq4sxmIGIAazoM3vN6Wh/7AeUozyG3YeOjls/khZ0S6ejkEPZ9RwJnleDFPvyEOkDjAAQM1AYzfZ6LNwHyO/bMRpyj8vYi7T2hojaT3yDBjG+l5B4VSlrN3OTwqrk7GXwK/Lc1LZBMl7j9coIEmFx57AG/w2tsE8TdhCqDcYInNxCrQaN6Y3g0uCpT6pzOEfg6+GWaa1NcVVt5KsXTUMGcSz7qh/bho0SmbXBvV/dkE/81esU68NyJsd2PORHhtowKiSjdibYabsPDHNwAU3YD/cfHkySSaIVB8OpyTW1u+LvfobAoiWKWG5ZxraaRzf0ZT2S44g09m5Lw3R8D2ln0YAwn3o84QIpvQ7gFs2k86voUIDIvtE907oFPkhfaOfRjLxBcR/D 6RJXoY3m c42GYizGgbAk9tL4c0XZIKlvDi+io0Eo697M2Z1kZCNbdZLO+R44zqwTr8d9otKmhfJJaaiKJ7R4DsU8i25jPA3x8rQ== 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 10/2/25 11:00, Harry Yoo wrote: > On Thu, Oct 02, 2025 at 10:14:55AM +0200, Vlastimil Babka wrote: >> However... >> > Is this PREEMPT_RT ? >> > >> >> > __alloc_tagging_slab_alloc_hook+0xa0/0x300 >> >> > __kmalloc_cache_noprof+0x1c4/0x5c0 >> >> > __set_page_owner+0x10d/0x1c0 >> >> This is the part that puzzles me, where do we call kmalloc from >> __set_page_owner()? > > It's > > __set_page_owner() > -> inc_stack_record_count() > -> add_stack_record_to_list() > -> kmalloc(). Thanks, missed that. >> And in a way that it loses the GFP_KERNEL passed all the >> way? I don't even see a lib/stackdepot function here. > > Oh wait, we clear __GFP_RECLAIM on the first attempt to allocate > high-order slabs. so gfpflags_allow_spinning() returns false. Ah right! Dang, that's suboptimal that we intend to do an opportunistic attempt, but limit the allocations of supplementary objects this way. But I don't see how to avoid this without inventing new gfp flags.