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Mon, 1 Sep 2025 10:27:48 +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 baiDOiR1tWjcAQAAD6G6ig (envelope-from ); Mon, 01 Sep 2025 10:27:48 +0000 Date: Mon, 1 Sep 2025 11:27:47 +0100 From: Pedro Falcato To: Brendan Jackman Cc: "Liam R. Howlett" , Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/4] tools/include: Implement a couple of atomic_t ops Message-ID: References: <20250828-b4-vma-no-atomic-h-v2-0-02d146a58ed2@google.com> <20250828-b4-vma-no-atomic-h-v2-1-02d146a58ed2@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250828-b4-vma-no-atomic-h-v2-1-02d146a58ed2@google.com> X-Rspamd-Action: no action X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 3230D40003 X-Stat-Signature: wnxrpf6h9f6a8donuo78ce8pq513669f X-HE-Tag: 1756722470-169193 X-HE-Meta: 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 PmX/v+1e o+gDeuUysEAvioBeTI+gL44fjLf+auLOW3JQoTwq3/G+5KLfls8IFG5kia+qHlGLAG+8AMV10lomZT94aYPcGj90i1F+yUAs+5SvfMy8w2CSXx9IYeSoATiZ02v5Rvo/HoDaC7vHjeCbgcEmNHrZaDViPE9AboeI1Zgf8Dp6f+3CjM/g7jLub/nWfwcUBv8Hj5aiH5cZmknnUmAOTtlG6JagV5UbjGk+jA5j419NrIKVXNacdyrr6aRBq8FNy/b8VUVpHeB3gxMzrg+/ohxD4AGX9Gnc0bbApwpMT4UplaJtoCeW74SdTx9n7jf/D70hzQkE4nYNhZ9qm8Orvo0pQObSu7QNtejC5HTTwwLuRBkT+Watri/AsnudpKw== 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 Thu, Aug 28, 2025 at 12:27:58PM +0000, Brendan Jackman wrote: > The VMA tests need an operation equivalent to > atomic_inc_unless_negative() to implement a fake mapping_map_writable(). > Adding it will enable them to switch to the shared atomic headers and > simplify that fake implementation. > > In order to add that, also add atomic_try_cmpxchg() which can be used to > implement it. This is copied from Documentation/atomic_t.txt. Then, > implement atomic_inc_unless_negative() itself based on the > raw_atomic_dec_unless_positive() in > include/linux/atomic/atomic-arch-fallback.h. > > There's no present need for a highly-optimised version of this (nor any > reason to think this implementation is sub-optimal on x86) so just > implement this with generic C, no x86-specifics. > > Signed-off-by: Brendan Jackman Reviewed-by: Pedro Falcato LGTM, thanks! -- Pedro