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Sat, 6 May 2023 13:35:28 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.9.0-alpha0-386-g2404815117-fm-20230425.001-g24048151 Mime-Version: 1.0 Message-Id: <315e7ec2-169c-4c4b-93df-485380bc0852@app.fastmail.com> In-Reply-To: <20230505133426.d70a6599d9a729496b68a70c@linux-foundation.org> References: <20230503013608.2431726-1-nphamcs@gmail.com> <20230503013608.2431726-3-nphamcs@gmail.com> <20230505133426.d70a6599d9a729496b68a70c@linux-foundation.org> Date: Sat, 06 May 2023 19:35:05 +0200 From: "Arnd Bergmann" To: "Andrew Morton" , "Geert Uytterhoeven" Cc: "Nhat Pham" , "Johannes Weiner" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bfoster@redhat.com, "Matthew Wilcox" , linux-api@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v13 2/3] cachestat: implement cachestat syscall Content-Type: text/plain X-Rspamd-Queue-Id: D4DE31C0004 X-Stat-Signature: ykcnq96sbjfogi79xphfcgx4omado6j1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1683394531-182369 X-HE-Meta: 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 mmco3CZd ZMTr/Ypro1b6QZWP/s8Rf/PWDsW5RvOEsAmy/nLeIKJ80Qm2hS9f+6ocQADjMoCBxi+Ns/w5PquZd/RFRT2lr+vjoLY8BaM1WEctfQ7NqfByeULsA3nDV6ioTurImt4+6y/TjF5dZ6mkv2tf4b3KR44jDFnnAaE+n7eK73CsLpyA8ebqGFr8jzS18Zg== 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: On Fri, May 5, 2023, at 22:34, Andrew Morton wrote: > On Thu, 4 May 2023 19:26:11 +0200 Geert Uytterhoeven > wrote: > >> > arch/x86/entry/syscalls/syscall_32.tbl | 1 + >> > arch/x86/entry/syscalls/syscall_64.tbl | 1 + >> >> This should be wired up on each and every architecture. >> Currently we're getting >> >> :1567:2: warning: #warning syscall cachestat not implemented [-Wcpp] >> >> in linux-next for all the missing architectures. > > Is that wise? We risk adding a syscall to an architecture without the > arch maintainers and testers even knowing about it. > > The compile-time nag is there to inform the arch maintainers that a new > syscall is available and that they should wire it up, run the selftest > and then ship the code if they're happy with the result. The usual approach is for the author of a new syscall to include a patch with all the architecture specific changes and Cc the architecture maintainers for that. Note that half the architectures get the entry from include/uapi/asm-generic/unistd.h, so adding it there does not necessarily trigger adding each maintainer from scripts/get_maintainer.pl. The only real risk in adding a new syscall is passing __u64 register arguments that behave differently across architectures, or using pointers to data structures that require a compat handler on some architectures. I watch out for those as they get sent to me or the linux-arch list, and this one is fine. Arnd