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Tue, 6 Jan 2026 14:57:48 +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 kkMkJewiXWkLDwAAD6G6ig (envelope-from ); Tue, 06 Jan 2026 14:57:48 +0000 Message-ID: Date: Tue, 6 Jan 2026 15:57:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] mm: only interrupt taking all mm locks on fatal signal Content-Language: en-US To: =?UTF-8?Q?Michel_D=C3=A4nzer?= , "Liam R. Howlett" , Mikulas Patocka , Lorenzo Stoakes , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , Andrew Morton , David Hildenbrand , amd-gfx@lists.freedesktop.org, linux-mm@kvack.org, Jann Horn , Pedro Falcato References: <7whbqlfrwjr4z2d4bpny3rjyl5tetdyx7ccf52uvby7hgywoym@6l6m2xcytez7> 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: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5D23512000D X-Stat-Signature: mwt4pd877ymxrtmjyrujtsf5am6cp8mu X-Rspam-User: X-HE-Tag: 1767711470-974241 X-HE-Meta: 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 JS+l4r+4 zd1BJVXQQHjyJFJ8yhaIJ/xor2HWfINW1Au8HVAGmNqtIdJ9csQXfxeKEXXgosnfko2r+U2XKIFJoKBUgWGWd3XD2NnD+U3Hly+Pj6/jV8YiWxuXiKndwdJJLR7Up/a7Nz/Pl46OyWqgsJ4bNBn6iDgdgTA4eVFObO61341S8AD/BSl65DA92czCaeI3xezddV5WGrFweS31QnZrLVzkdSwqfEXy/qC4cAp9fnz/sMrrz5W2LNf+3pMUcyJ9htrCyHQ+riPqWTW8OW/yVeozDWl8z0/DzpdQKjqXlI9zatw8bUBOAQC/xYZ4UzvRfYA1lgOLWynNRhjUIWUh8wJW3tq7EDg== 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 1/6/26 12:36, Michel Dänzer wrote: > On 1/5/26 19:15, Liam R. Howlett wrote: >> * Mikulas Patocka [260104 16:17]: >> >> I'm not saying it's wrong to change the signal handling, but this is >> very much working around a bug in userspace constantly hammering a task >> with signals and then is surprised there is a response that the kernel >> was interrupted. > > I'd go further than that. If user space fails to retry the system call > in response to -EINTR, that's a user-space bug, period. It can happen > anytime for any number of other reasons. (That most system calls happen > to get away without it most of the time doesn't make it not a bug) > > (This is assuming the system call can be safely retried, otherwise > returning -EINTR to user space for non-fatal signals would be a kernel > bug) This is true and the userspace should be fixed. But the kernel still tries hard to support even broken userspace. Even though commit 7906d00cd1f6 is very old now, from 2.6.27, we could say that technically it violated the "do not break userspace" rule. It's not always easy to undo such breakages, especially after many years, and if some other userspace meanwhile starts depending on the new behavior. But I doubt that's the case here and anything will have issues with non-fatal signals being delayed. >>> I'm submitting this patch for the stable kernels, because this bug may >>> cause random failures in any code that calls mm_take_all_locks. >> >> They aren't random failures, they are a response to a signal sent to the >> process that may be taking a very long time to do something. >> >> I really don't see how continuously sending signals at a short interval >> interrupting system calls can be considered random failures, especially >> when the return is -EINTR which literally means "Interrupted system >> call". How else would you interrupt a system call, if not a signal? >> >> I feel like we are making the code less versatile to work around the >> fact that userspace didn't realise that system calls could be >> interrupted without a fatal signal. >> >> And from that view, I consider this a functional change and not a bug >> fix. > > I agree. > >