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Mon, 5 Jan 2026 19:19:03 +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 qU36EacOXGlbPAAAD6G6ig (envelope-from ); Mon, 05 Jan 2026 19:19:03 +0000 Message-ID: <56598d76-02ca-490f-a100-0f223fb5717e@suse.cz> Date: Mon, 5 Jan 2026 20:19:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: fix kmalloc_nolock() context check for PREEMPT_RT Content-Language: en-US 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> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: A90C0180003 X-Stat-Signature: px5kikdh9zqip6hb9j4bbdeoufu6r1ya X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1767640745-357945 X-HE-Meta: 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 09G5D8E7 aiReGqb2hSkSB80RAwME2gpcG8NsOcccOZIuwBIGQPjYcFPlkEhjrIFIQTFoNVJKq1pSyBkrhzFGzQQfkt09uUYwdJq1n5hp5551C34lro4LflreUz4a7IXCuZGGWsdzSouA2aHccFfs4RuAB5uo8hcahYQIdgIUzhKMBqb7YRQ6TKpiIP33uVHiUsuvX9zDwUnyO5ElEx3ngKuV71EfIu65ufEXGQ69qOj+DOjdiL7KwwUS7nS/+iiStfMl3Wv5XHVhlanED0WKeAhSKLDoB3+Cr0x4VmksxeST5vwo7NkBfHhiJ26ewgpD3RTJsJoP2t7fP3ngbCgApdMbmCj2dNzv76nmOsMSoaElIhUiNe0xt52LQjkDS9+dqcxsbXmxxMrK792KgMWEYcpVvJj+rmywIPLqzx410fHnrf3ARGeevdFxc0CdwXNQn6R01Uha0bgi9bd4ucaOYpi8= 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 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. 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