From: "David Hildenbrand (Arm)" <david@kernel•org>
To: Tejun Heo <tj@kernel•org>, David Vernet <void@manifault•com>,
Andrea Righi <arighi@nvidia•com>,
Changwoo Min <changwoo@igalia•com>,
Alexei Starovoitov <ast@kernel•org>,
Andrii Nakryiko <andrii@kernel•org>,
Daniel Borkmann <daniel@iogearbox•net>,
Martin KaFai Lau <martin.lau@linux•dev>,
Kumar Kartikeya Dwivedi <memxor@gmail•com>
Cc: Peter Zijlstra <peterz@infradead•org>,
Catalin Marinas <catalin.marinas@arm•com>,
Will Deacon <will@kernel•org>, Thomas Gleixner <tglx@kernel•org>,
Ingo Molnar <mingo@redhat•com>, Borislav Petkov <bp@alien8•de>,
Dave Hansen <dave.hansen@linux•intel.com>,
Andrew Morton <akpm@linux-foundation•org>,
Mike Rapoport <rppt@kernel•org>,
Emil Tsalapatis <emil@etsalapatis•com>,
sched-ext@lists•linux.dev, bpf@vger•kernel.org, x86@kernel•org,
linux-arm-kernel@lists•infradead.org, linux-mm@kvack•org,
linux-kernel@vger•kernel.org
Subject: Re: [PATCH 1/8] mm: Add ptep_try_set() for lockless empty-slot installs
Date: Sat, 23 May 2026 00:07:04 +0200 [thread overview]
Message-ID: <6ca116f4-b9e2-4ad3-a232-bc441f88bc82@kernel.org> (raw)
In-Reply-To: <20260522172219.1423324-2-tj@kernel.org>
>
> +#ifndef ptep_try_set
> +/**
> + * ptep_try_set - atomically set an empty kernel PTE
> + * @ptep: page table entry
> + * @new_pte: value to install
> + *
> + * Atomically set *@ptep to @new_pte iff *@ptep is pte_none(). Return true on
> + * success, false if the slot was already populated or the arch has no
> + * implementation.
> + *
> + * For special kernel page tables only - never user page tables. The caller must
> + * prevent concurrent teardown of @ptep and must accept that other writers may
> + * race. Concurrent clearers must use ptep_get_and_clear() so racing accesses
> + * agree on the outcome.
> + *
> + * Architectures opt in by providing a cmpxchg-based override and defining
> + * ptep_try_set as an identity macro. The generic stub returns false, which is
> + * correct for callers that fall through to oops on failure.
> + */
> +static inline bool ptep_try_set(pte_t *ptep, pte_t new_pte)
There are only a handful of valid use cases for this (and the "fall through to
oops on failure") makes this very clear.
So I'm fine with this, assuming there won't really be a lot of other users
besides ebpf.
Acked-by: David Hildenbrand (arm) <david@kernel•org>
--
Cheers,
David
next prev parent reply other threads:[~2026-05-22 22:07 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-22 17:22 [PATCHSET v4 sched_ext/for-7.2] bpf/arena: Direct kernel-side access Tejun Heo
2026-05-22 17:22 ` [PATCH 1/8] mm: Add ptep_try_set() for lockless empty-slot installs Tejun Heo
2026-05-22 22:07 ` David Hildenbrand (Arm) [this message]
2026-05-25 15:50 ` patchwork-bot+netdevbpf
2026-05-22 17:22 ` [PATCH 2/8] bpf: Recover arena kernel faults with scratch page Tejun Heo
2026-05-26 12:45 ` David Hildenbrand (Arm)
2026-05-28 21:30 ` Alexei Starovoitov
2026-05-29 18:12 ` Tejun Heo
2026-05-29 18:38 ` Alexei Starovoitov
2026-05-29 18:44 ` Tejun Heo
2026-05-31 17:47 ` Tejun Heo
2026-05-31 18:58 ` David Hildenbrand (Arm)
2026-06-01 0:16 ` Alexei Starovoitov
2026-05-22 17:22 ` [PATCH 3/8] bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers Tejun Heo
2026-05-22 17:22 ` [PATCH 4/8] bpf: Add bpf_struct_ops_for_each_prog() Tejun Heo
2026-05-22 17:22 ` [PATCH 5/8] bpf/arena: Add bpf_arena_map_kern_vm_start() and bpf_prog_arena() Tejun Heo
2026-05-22 17:22 ` [PATCH 6/8] sched_ext: Require an arena for cid-form schedulers Tejun Heo
2026-05-22 17:22 ` [PATCH 7/8] sched_ext: Sub-allocator over kernel-claimed BPF arena pages Tejun Heo
2026-05-22 17:22 ` [PATCH 8/8] sched_ext: Convert ops.set_cmask() to arena-resident cmask Tejun Heo
2026-05-25 15:45 ` [PATCHSET v4 sched_ext/for-7.2] bpf/arena: Direct kernel-side access Alexei Starovoitov
2026-05-25 19:54 ` Tejun Heo
-- strict thread matches above, loose matches on Subject: below --
2026-05-20 23:50 [PATCHSET v3 " Tejun Heo
2026-05-20 23:50 ` [PATCH 1/8] mm: Add ptep_try_set() for lockless empty-slot installs Tejun Heo
2026-05-21 7:00 ` Andrea Righi
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