From patchwork Fri Apr 16 09:24:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 43016 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 1616E396E84E; Fri, 16 Apr 2021 09:23:54 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1616E396E84E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1618565034; bh=5lWMeGxdVa7MME0Q+vt1vnbDYRXk8TdCP2Vv2B+JtF4=; h=To:Subject:In-Reply-To:References:Date:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=aMLZGaZM8zfvOIsvo3K1s5xF/kZdyNpAFyTfi7lh923xqJoU/y38A2wRQlbx0HwvM a3yTe1WZR5p1qiHuhx2vyy0tGtC8RF8AC59hXKJ8X0JckaPzhIhyulaau4UxitTN3P lYdJPK5umbXam1R3UfguJZs5DwfV3A/rSELCMObM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id E28C13968C18 for ; Fri, 16 Apr 2021 09:23:50 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org E28C13968C18 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-78-9llqai9EOVSqtQCpppay0Q-1; Fri, 16 Apr 2021 05:23:48 -0400 X-MC-Unique: 9llqai9EOVSqtQCpppay0Q-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E74C7107ACC7 for ; Fri, 16 Apr 2021 09:23:47 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-113-139.ams2.redhat.com [10.36.113.139]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 19F79100E113 for ; Fri, 16 Apr 2021 09:23:46 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH v4 33/37] x86: Remove low-level lock optimization In-Reply-To: References: Message-Id: <24b83fba24f43c3a200addb13b6e6c6aa2f28ff3.1618564630.git.fweimer@redhat.com> Date: Fri, 16 Apr 2021 11:24:04 +0200 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP 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: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" The current approach is to do this optimizations at a higher level, in generic code, so that single-threaded cases can be specifically targeted. Furthermore, using IS_IN (libc) as a compile-time indicator that all locks are private is no longer correct once process-shared lock implementations are moved into libc. The generic is not compatible with assembler code (obviously), so it's necessary to remove two long-unused #includes. Reviewed-by: Adhemerval Zanella --- sysdeps/i386/nptl/pthread_spin_lock.S | 1 - sysdeps/unix/sysv/linux/x86/lowlevellock.h | 87 ---------------------- sysdeps/x86_64/nptl/pthread_spin_lock.S | 1 - 3 files changed, 89 deletions(-) delete mode 100644 sysdeps/unix/sysv/linux/x86/lowlevellock.h diff --git a/sysdeps/i386/nptl/pthread_spin_lock.S b/sysdeps/i386/nptl/pthread_spin_lock.S index eec157fde7..985b236aae 100644 --- a/sysdeps/i386/nptl/pthread_spin_lock.S +++ b/sysdeps/i386/nptl/pthread_spin_lock.S @@ -16,7 +16,6 @@ . */ #include -#include ENTRY (pthread_spin_lock) mov 4(%esp), %eax diff --git a/sysdeps/unix/sysv/linux/x86/lowlevellock.h b/sysdeps/unix/sysv/linux/x86/lowlevellock.h deleted file mode 100644 index 7205bcadfd..0000000000 --- a/sysdeps/unix/sysv/linux/x86/lowlevellock.h +++ /dev/null @@ -1,87 +0,0 @@ -/* Low-level lock implementation, x86 version. - Copyright (C) 2019-2021 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - . */ - -#ifndef _X86_64_LOWLEVELLOCK_H -#define _X86_64_LOWLEVELLOCK_H 1 - -#ifndef __ASSEMBLER__ -#include -#include - -/* The lll_trylock, lll_lock, and lll_unlock implements a single-thread - optimization using the cmpxchgl instruction. It checks if the process - is single thread and avoid a more expensive atomic instruction. */ - -/* The single-thread optimization only works for libc itself, we need - atomicity for libpthread in case of shared futexes. */ -#if !IS_IN(libc) -# define is_single_thread 0 -#else -# define is_single_thread SINGLE_THREAD_P -#endif - -/* In the __lllc_as we simply return the value in %eax after the cmpxchg - instruction. In case the operation succeeded this value is zero. In case - the operation failed, the cmpxchg instruction has loaded the current value - of the memory work which is guaranteed to be nonzero. */ -static inline int -__attribute__ ((always_inline)) -__lll_cas_lock (int *futex) -{ - int ret; - asm volatile ("cmpxchgl %2, %1" - : "=a" (ret), "=m" (*futex) - : "r" (1), "m" (*futex), "0" (0) - : "memory"); - return ret; -} - -#undef lll_trylock -#define lll_trylock(lock) \ - ({ \ - int __ret; \ - if (is_single_thread) \ - __ret = __lll_cas_lock (&(lock)); \ - else \ - __ret = __lll_trylock (&(lock)); \ - __ret; \ - }) - -#undef lll_lock -#define lll_lock(lock, private) \ - ((void) \ - ({ \ - if (is_single_thread) \ - __lll_cas_lock (&(lock)); \ - else \ - __lll_lock (&(lock), private); \ - })) - -#undef lll_unlock -#define lll_unlock(lock, private) \ - ((void) \ - ({ \ - if (is_single_thread) \ - (lock)--; \ - else \ - __lll_unlock (&(lock), private); \ - })) - -#endif /* !__ASSEMBLER__ */ - -#endif /* lowlevellock.h */ diff --git a/sysdeps/x86_64/nptl/pthread_spin_lock.S b/sysdeps/x86_64/nptl/pthread_spin_lock.S index 66cbbc5252..ff5e7525ca 100644 --- a/sysdeps/x86_64/nptl/pthread_spin_lock.S +++ b/sysdeps/x86_64/nptl/pthread_spin_lock.S @@ -15,7 +15,6 @@ License along with the GNU C Library; if not, see . */ -#include #include ENTRY(pthread_spin_lock)