From patchwork Fri Jun 12 18:51:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Andr=C3=A9_Almeida?= X-Patchwork-Id: 39586 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 1BD59395B435; Fri, 12 Jun 2020 18:51:26 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1BD59395B435 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1591987886; bh=FeeEG+nZmQdyGHkMDJj0v/CLc/IPMaPh/lSElOWzBV0=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=j1ROkhalv4PdDrMEHyJzTboW+gSBOg/uJZPiRRxm8IG++3QSAAOfSP84Uf0B0sTzi ViDyDusCreuV7I3h+/TOTozWGk29Wwd88tyNDPHuqTyv9MyHBiuISOG4vNa67rnz1T RiGMxVXqRXQl8qsqdrqYQh/K6xYXUlFCNM8Qargs= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [46.235.227.227]) by sourceware.org (Postfix) with ESMTPS id C375E3851C36 for ; Fri, 12 Jun 2020 18:51:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org C375E3851C36 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: tonyk) with ESMTPSA id 52F862A5160 To: linux-kernel@vger.kernel.org, tglx@linutronix.de, peterz@infradead.org Subject: [RFC 0/4] futex2: Add new futex interface Date: Fri, 12 Jun 2020 15:51:18 -0300 Message-Id: <20200612185122.327860-1-andrealmeid@collabora.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Spam-Status: No, score=-3.3 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, RCVD_IN_DNSWL_NONE, SPF_HELO_PASS, SPF_PASS, TXREP, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: =?utf-8?q?Andr=C3=A9_Almeida_via_Libc-alpha?= From: =?utf-8?q?Andr=C3=A9_Almeida?= Reply-To: =?utf-8?q?Andr=C3=A9_Almeida?= Cc: fweimer@redhat.com, malteskarupke@web.de, libc-alpha@sourceware.org, linux-api@vger.kernel.org, mingo@redhat.com, andrealmeid@collabora.com, dvhart@infradead.org, kernel@collabora.com, krisman@collabora.com, pgriffais@valvesoftware.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Hello, This RFC is a followup to the previous discussion initiated from my last patch "futex: Implement mechanism to wait on any of several futexes"[1]. As stated in the thread, the correct approach to move forward with the wait multiple operation would be to create a new syscall that would have all new cool features. The first patch adds the new interface and just translate the call for the old interface, without implementing new features. The goal here is to establish the interface and to check if everyone is happy with this API. The rest of patches are selftests to show the interface in action. I have the following questions: - Has anyone stared worked on a implementation of this interface? If yes, it would be nice to share the progress so we don't have duplicated work. - What suggestions do you have to implement this? Start from scratch or reuse the most code possible? - The interface seems correct and implements the requirements asked by you? - The proposed interface uses ktime_t type for absolute timeout, and I assumed that it should use values in a nsec resolution. If this is true, we have some problems with i386 ABI, please check out the COMPAT_32BIT_TIME implementation in patch 1 for more details. I haven't added a time64 implementation yet, until this is clarified. - Is expected to have a x32 ABI implementation as well? In the case of wait and wake, we could use the same as x86_64 ABI. However, for the waitv (aka wait on multiple futexes) we would need a proper x32 entry since we are dealing with 32bit pointers. Those are the cool new features that this syscall should address some day: - Operate with variable bit size futexes, not restricted to 32: 8, 16 and 64 - Wait on multiple futexes, using the following semantics: struct futex_wait { void *uaddr; unsigned long val; unsigned long flags; }; sys_futex_waitv(struct futex_wait *waiters, unsigned int nr_waiters, unsigned long flags, ktime_t *timo); - Have NUMA optimizations: if FUTEX_NUMA_FLAG is present, the `void *uaddr` argument won't be a u{8, 16, 32, 64} value anymore, but a struct containing a NUMA node hint: struct futex32_numa { u32 value __attribute__ ((aligned (8))); u32 hint; }; struct futex64_numa { u64 value __attribute__ ((aligned (16))); u64 hint; }; Thanks, André André Almeida (4): futex2: Add new futex interface selftests: futex: Add futex2 wake/wait test selftests: futex: Add futex2 timeout test selftests: futex: Add futex2 wouldblock test MAINTAINERS | 2 +- arch/x86/entry/syscalls/syscall_32.tbl | 2 + arch/x86/entry/syscalls/syscall_64.tbl | 2 + include/linux/syscalls.h | 9 ++ include/uapi/asm-generic/unistd.h | 7 +- include/uapi/linux/futex.h | 10 ++ init/Kconfig | 7 ++ kernel/Makefile | 1 + kernel/futex2.c | 97 ++++++++++++++++ kernel/sys_ni.c | 5 + tools/include/uapi/asm-generic/unistd.h | 7 +- .../selftests/futex/functional/.gitignore | 1 + .../selftests/futex/functional/Makefile | 4 +- .../selftests/futex/functional/futex2_wait.c | 106 ++++++++++++++++++ .../futex/functional/futex_wait_timeout.c | 27 ++++- .../futex/functional/futex_wait_wouldblock.c | 34 +++++- .../testing/selftests/futex/functional/run.sh | 3 + .../selftests/futex/include/futex2test.h | 50 +++++++++ 18 files changed, 361 insertions(+), 13 deletions(-) create mode 100644 kernel/futex2.c create mode 100644 tools/testing/selftests/futex/functional/futex2_wait.c create mode 100644 tools/testing/selftests/futex/include/futex2test.h