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Tue, 13 Jan 2026 13:59:38 +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 bPbZIspPZmnvMAAAD6G6ig (envelope-from ); Tue, 13 Jan 2026 13:59:38 +0000 Message-ID: Date: Tue, 13 Jan 2026 14:59:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: fix kmalloc_nolock() context check for PREEMPT_RT From: Vlastimil Babka To: Swaraj Gaikwad , lgoncalv@redhat.com Cc: akpm@linux-foundation.org, ast@kernel.org, bigeasy@linutronix.de, cl@gentwo.org, clrkwllms@kernel.org, david.hunter.linux@gmail.com, harry.yoo@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev, rientjes@google.com, roman.gushchin@linux.dev, rostedt@goodmis.org, skhan@linuxfoundation.org, syzbot+b1546ad4a95331b2101e@syzkaller.appspotmail.com, Hao Li References: <20251219135143.7337-1-swarajgaikwad1925@gmail.com> <56598d76-02ca-490f-a100-0f223fb5717e@suse.cz> Content-Language: en-US In-Reply-To: <56598d76-02ca-490f-a100-0f223fb5717e@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: u3bdrpc4qwogfbc9pssmrf843w1cwdam X-Rspam-User: X-Rspamd-Queue-Id: 83B59C0008 X-Rspamd-Server: rspam08 X-HE-Tag: 1768312780-41818 X-HE-Meta: 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 yg5nb5Jv SRwdzCr+xy9UeifCrlYe8CW7LehV6uTs55CuSy2eDA4T+5Z1dvTrS5NAmztbWsUtkUatKCx/9AZDX8zpwNXiFjEpH4rLc3k8zFcwurXYIZ4Am4ShMTBib326h8dyOBla/lirGv1r4m8KpJYzOVSnRt/wk1JBUp02I3qKe6KEOg0nGGH6MAQpGMncsr0JM+Ts0J07M9Ej1+fLAkje/xLW327X948YD0fW/Uq0471V42EepSv7ffTdvcOf6FWMyLJmKS2RLDkxr4h4XjjyjtMc3bM8p7d5860j5Vad1lslArNNAMTJ/0buXMSjWXp8NBBfQudCW3UE+qRubHPdUAPmGtSOBn8ujjdCkKmaobtzSSYE8aUlnfztow06LZszvNhBjxCGNRAoOye5pO63ArAQyWCY1Qo2l7vZdPaq363ZPJBTNcGmk2cLnhTrxQG6tLhj7We0SwzqEmU2Mmyc= 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 1/5/26 8:19 PM, Vlastimil Babka wrote: > On 12/19/25 14:51, Swaraj Gaikwad wrote: >> I agree that we can simplify this. I think !preemptible() would be >> the most descriptive choice here, as it directly expresses the >> constraint, we cannot take a sleeping lock when preemption is >> disabled. >> The updated check would be: >> if (IS_ENABLED(CONFIG_PREEMPT_RT) && !preemptible()) >> >> I'll send a v2 with this change unless there are objections. Ping? Are you planning to? Otherwise we have to do it ourselves as we can't leave things broken? Also Sebastian do you agree? Thanks. > I think it's the best solution for now, so please do. We can change it back > later with sheaves, as Hao Li pointed out. It will limit PREEMPT_RT > kmalloc_nolock() for now. Steven explained to me it's the tracepoints > disabling preemption, but that will be also improved soon: > > https://lore.kernel.org/all/20251219120607.7371034e@gandalf.local.home/ > > >> Swaraj >