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Fri, 22 Sep 2023 06:56:30 -0700 (PDT) Received: from [192.168.1.94] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id l13-20020a02cd8d000000b0042b05586c52sm1028681jap.25.2023.09.22.06.56.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Sep 2023 06:56:29 -0700 (PDT) Message-ID: Date: Fri, 22 Sep 2023 07:56:28 -0600 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 10/15] futex: Add sys_futex_requeue() Content-Language: en-US To: Peter Zijlstra , Ingo Molnar Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@redhat.com, dvhart@infradead.org, dave@stgolabs.net, andrealmeid@igalia.com, Andrew Morton , urezki@gmail.com, hch@infradead.org, lstoakes@gmail.com, Arnd Bergmann , linux-api@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, malteskarupke@web.de, Geert Uytterhoeven References: <20230921104505.717750284@noisy.programming.kicks-ass.net> <20230921105248.511860556@noisy.programming.kicks-ass.net> <20230922110335.GC7080@noisy.programming.kicks-ass.net> From: Jens Axboe In-Reply-To: <20230922110335.GC7080@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D178814001B X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: a575zjw74a7ua6om88b8s6pg5pgn1mpy X-HE-Tag: 1695390991-338756 X-HE-Meta: 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 tW4jRKWS 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 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 9/22/23 5:03 AM, Peter Zijlstra wrote: > On Fri, Sep 22, 2023 at 11:35:03AM +0200, Ingo Molnar wrote: >> >> * peterz@infradead.org wrote: >> >>> --- linux-2.6.orig/kernel/futex/syscalls.c >>> +++ linux-2.6/kernel/futex/syscalls.c >>> @@ -396,6 +396,44 @@ SYSCALL_DEFINE6(futex_wait, >>> return ret; >>> } >>> >>> +/* >>> + * sys_futex_requeue - Requeue a waiter from one futex to another >>> + * @waiters: array describing the source and destination futex >>> + * @flags: unused >>> + * @nr_wake: number of futexes to wake >>> + * @nr_requeue: number of futexes to requeue >>> + * >>> + * Identical to the traditional FUTEX_CMP_REQUEUE op, except it is part of the >>> + * futex2 family of calls. >>> + */ >>> + >>> +SYSCALL_DEFINE4(futex_requeue, >>> + struct futex_waitv __user *, waiters, >>> + unsigned int, flags, >>> + int, nr_wake, >>> + int, nr_requeue) >>> +{ >>> + struct futex_vector futexes[2]; >>> + u32 cmpval; >>> + int ret; >>> + >>> + if (flags) >>> + return -EINVAL; >> >> Small detail, but isn't -ENOSYS the canonical error code for functionality >> not yet implemented - which the unused 'flags' ABI is arguably? >> >> -EINVAL is for recognized but incorrect parameters, such as: > > IIUC 'unknown flag' falls into the -EINVAL return category. Here we > happen to have no known flags, but that should not matter. Yep, -ENOSYS is for not having the syscall at all, -EINVAL for unknown flags set. -- Jens Axboe