From patchwork Fri Jun 25 08:10:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kurt Kanzenbach X-Patchwork-Id: 44011 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 459DF385AC22 for ; Fri, 25 Jun 2021 08:11:50 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 459DF385AC22 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1624608710; bh=KgO3ZkGQGjp275Naj0EK/ncAuq/lwiaM+tO6iPj5igo=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=DF5QUZFgYkUuem/xlrQVjbICM/1m9nntG0mAqTGzLQKo+5z/OTJoyVt4GZvzdVtMj 34U8U+eYJY6awf9cFzoaqDygrijFPSaYe2UHZKCxFMoHkYtYSaEvAYDhJX59xxChR4 MMlBrIiHDOHJ0n5EqtB92nP3SDThBA0iDZLMAjJA= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by sourceware.org (Postfix) with ESMTPS id 5AA643858001 for ; Fri, 25 Jun 2021 08:11:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 5AA643858001 To: libc-alpha@sourceware.org Subject: [PATCH v1 0/6] nptl: Introduce and use FUTEX_LOCK_PI2 Date: Fri, 25 Jun 2021 10:10:58 +0200 Message-Id: <20210625081104.1134598-1-kurt@linutronix.de> MIME-Version: 1.0 X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_NUMSUBJECT, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no 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: Kurt Kanzenbach via Libc-alpha From: Kurt Kanzenbach Reply-To: Kurt Kanzenbach Cc: Florian Weimer , Sebastian Andrzej Siewior , Kurt Kanzenbach , Peter Zijlstra , Thomas Gleixner , Joseph Myers Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" Linux real time applications often make use of mutexes with priority inheritance enabled due to problems such as unbounded priority inversion. In addition, some applications make use of timeouts e.g., by utilizing pthread_mutex_clocklock(). However, the combination of priority inheritance enabled mutexes with timeouts based on CLOCK_MONOTONIC doesn't work. That is because the underlying Linux kernel futex interface didn't support it, yet. Using CLOCK_REALTIME is possible, but it is subject to adjustments (NTP, PTP, ...). Therefore, Thomas proposed and introduced a new futex operation called FUTEX_LOCK_PI2 with support for selectable clocks [1]. Here is a proof of concept patch set adding FUTEX_LOCK_PI2 in order to support pthread_mutex_clocklock(MONOTONIC)/PI. The idea is to use futex_lock_pi2() by default, and fallback to futex_lock_pi() in case the kernel is too old. There's also a bugreport for glibc with a test case: https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Changes since RFC: * FUTEX_LOCK_PI2 merged in upstream Linux kernel (Thomas Gleixner, Peter Zijlstra) * Make of __ASSUME_FUTEX_LOCK_PI2 in the implementation (Adhemerval Zanella) * Get rid of probing for FUTEX_LOCK_PI2 in timedlock (Adhemerval Zanella) * Adjust the test cases (Adhemerval Zanella) * Use correct Linux kernel version (Joseph Myers) Previous versions: * https://sourceware.org/pipermail/libc-alpha/2021-June/127798.html Thanks, Kurt [1] - https://lkml.kernel.org/lkml/20210422194417.866740847@linutronix.de/ Kurt Kanzenbach (6): Linux: Add FUTEX_LOCK_PI2 nptl: Introduce futex_lock_pi2() nptl: Use futex_lock_pi2() nptl: Remove mutex test 10 nptl: mutex-test5: Include CLOCK_MONOTONIC for PI nptl: mutex-test9: Include CLOCK_MONOTONIC for PI nptl/Makefile | 2 +- nptl/pthread_mutex_timedlock.c | 10 +- nptl/tst-mutexpi10.c | 68 ----------- sysdeps/nptl/futex-internal.h | 131 ++++++++++++++++++++++ sysdeps/nptl/lowlevellock-futex.h | 1 + sysdeps/pthread/tst-mutex5.c | 20 +++- sysdeps/pthread/tst-mutex9.c | 9 +- sysdeps/unix/sysv/linux/kernel-features.h | 8 ++ 8 files changed, 163 insertions(+), 86 deletions(-) delete mode 100644 nptl/tst-mutexpi10.c