From: Michal Hocko <mhocko@suse.com>
To: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: akpm@linux-foundation.org, david@kernel.org,
lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com,
vbabka@suse.cz, rppt@kernel.org, surenb@google.com,
ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org,
yonghong.song@linux.dev, john.fastabend@gmail.com,
kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com,
jolsa@kernel.org, jackmanb@google.com, hannes@cmpxchg.org,
ziy@nvidia.com, bigeasy@linutronix.de, clrkwllms@kernel.org,
rostedt@goodmis.org, catalin.marinas@arm.com, will@kernel.org,
ryan.roberts@arm.com, kevin.brodsky@arm.com, dev.jain@arm.com,
yang@os.amperecomputing.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-rt-devel@lists.linux.dev,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] arm64: mmu: use pagetable_alloc_nolock() while stop_machine()
Date: Thu, 18 Dec 2025 10:30:33 +0100 [thread overview]
Message-ID: <aUPJuZINNuNxddRX@tiehlicka> (raw)
In-Reply-To: <20251212161832.2067134-3-yeoreum.yun@arm.com>
On Fri 12-12-25 16:18:32, Yeoreum Yun wrote:
> linear_map_split_to_ptes() and __kpti_install_ng_mappings()
> are called as callback of stop_machine().
> That means these functions context are preemption disabled.
>
> Unfortunately, under PREEMPT_RT, the pagetable_alloc() or
> __get_free_pages() couldn't be called in this context
> since spin lock that becomes sleepable on RT,
> potentially causing a sleep during page allocation.
>
> To address this, pagetable_alloc_nolock().
As you cannot tolerate allocation failure and this is pretty much
permanent allocation (AFAIU) why don't you use a static allocation?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2025-12-18 9:30 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-12 16:18 [PATCH 0/2] introduce pagetable_alloc_nolock() Yeoreum Yun
2025-12-12 16:18 ` [PATCH 1/2] mm: " Yeoreum Yun
2025-12-12 16:18 ` [PATCH 2/2] arm64: mmu: use pagetable_alloc_nolock() while stop_machine() Yeoreum Yun
2025-12-13 7:05 ` Brendan Jackman
2025-12-14 9:13 ` Yeoreum Yun
2025-12-15 9:22 ` Brendan Jackman
2025-12-15 9:34 ` Yeoreum Yun
2025-12-15 9:55 ` Brendan Jackman
2025-12-15 10:06 ` Yeoreum Yun
2025-12-16 10:10 ` Brendan Jackman
2025-12-16 11:03 ` Yeoreum Yun
2025-12-16 11:26 ` Brendan Jackman
2025-12-16 12:01 ` Yeoreum Yun
2025-12-16 12:39 ` Brendan Jackman
2025-12-16 13:25 ` Yeoreum Yun
2025-12-18 9:30 ` Michal Hocko [this message]
2025-12-18 9:36 ` Yeoreum Yun
2025-12-18 12:02 ` Ryan Roberts
2025-12-18 12:17 ` Michal Hocko
2025-12-18 12:24 ` Yeoreum Yun
2025-12-16 15:11 ` [PATCH 0/2] introduce pagetable_alloc_nolock() Ryan Roberts
2025-12-16 16:52 ` Yeoreum Yun
2025-12-17 9:34 ` Ryan Roberts
2025-12-17 10:48 ` Yeoreum Yun
2025-12-17 12:04 ` Ryan Roberts
2025-12-17 12:52 ` Yeoreum Yun
2025-12-17 13:15 ` Vlastimil Babka
2025-12-17 13:35 ` Brendan Jackman
2025-12-17 13:56 ` Yeoreum Yun
2025-12-17 15:10 ` Vlastimil Babka
2025-12-17 17:19 ` Brendan Jackman
2025-12-18 7:47 ` Vlastimil Babka
2025-12-18 7:52 ` David Hildenbrand (Red Hat)
2025-12-23 22:59 ` Yang Shi
2025-12-24 7:00 ` Yeoreum Yun
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