From patchwork Mon Jul 13 17:10:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella Netto X-Patchwork-Id: 40077 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 51179389041E; Mon, 13 Jul 2020 17:10:50 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 51179389041E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1594660250; bh=rwY4/LAvDgUQ4QRd4RvWM020cbtnwvb1urivhs24a7w=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=NSmmRS5EW87AvIeQrXL9grkT8+wI21zh40MvVs6zXfMOH11gIdEpo/NYANkRfvDNh f2aqvfCWAIi2KcI3XYwmkin1MJzNwqFOyNFSaS5aYM5XMM2iShFBPQobeiDohya9LD DUViFFZO9xA2p2Ef5zgk93wxmA01G7psghJqkwqQ= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-qv1-xf41.google.com (mail-qv1-xf41.google.com [IPv6:2607:f8b0:4864:20::f41]) by sourceware.org (Postfix) with ESMTPS id F33FD388E829 for ; Mon, 13 Jul 2020 17:10:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org F33FD388E829 Received: by mail-qv1-xf41.google.com with SMTP id dm12so6104310qvb.9 for ; Mon, 13 Jul 2020 10:10:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=rwY4/LAvDgUQ4QRd4RvWM020cbtnwvb1urivhs24a7w=; b=kkLArYr2AEyIyV8U1NuWebdH/4HaTlYNNxkPt5GN5a4jYIE8Fk7jlqRdtYeqESSLxS 5yJcXWaN8BqiUPm3e2mql/HPh4kVApJJh85uKm7zDJeFgn4Xzcg179xXPBYXS+Hm6M3U DgPrl3RLLmdP0il4Yhw30VsPIBVRuBMGy8ohCMaWGCXLZYiSfhE/mftRoMK9kqcqMQnM Q4fseJXcArE3MVH4J8S6v6LApBHjkYy6sNuumtiD2v2O8+PXASApF58l4zjBbS++AjuO 70iRx0rIVW3JCLN4DK3xEcPtgVtS4v04tfoiotvFVCuKoOiV4WIM4SXxmQu7dBNOf1as C1Bw== X-Gm-Message-State: AOAM5329vQoB2BnPJWkUczeYCV7/meFNoVHpM8HSo+W2rvH/QL2H6C78 MAiv3etX0Da5PJIiIz9B5e1DRonMgD8= X-Google-Smtp-Source: ABdhPJyXir4k7BjM2QeVu37P4LvbeTrBqjE5hQxNkM74BVludOYJ06akwpo0FYEmVMuVPG7BK7p0Iw== X-Received: by 2002:a0c:b520:: with SMTP id d32mr482557qve.6.1594660247220; Mon, 13 Jul 2020 10:10:47 -0700 (PDT) Received: from localhost.localdomain ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id v10sm19767919qtk.14.2020.07.13.10.10.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2020 10:10:46 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH 12/23] linux: Add helper function to optimize 64-bit time_t fallback support Date: Mon, 13 Jul 2020 14:10:14 -0300 Message-Id: <20200713171025.3661832-12-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200713171025.3661832-1-adhemerval.zanella@linaro.org> References: <20200713171025.3661832-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-14.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, 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: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Netto Reply-To: Adhemerval Zanella Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" These helper functions are used to optimize the 64-bit time_t support on configurations that requires support for 32-bit time_t fallback (!__ASSUME_TIME64_SYSCALLS). The idea is once the kernel advertises that it does not have 64-bit time_t support, glibc will stop to try issue the 64-bit time_t syscall altogether. For instance: #ifndef __NR_symbol_time64 # define __NR_symbol_time64 __NR_symbol #endif int r; if (supports_time64 ()) { r = INLINE_SYSCALL_CALL (symbol, ...); if (r == 0 || errno != ENOSYS) return r; mark_time64_unsupported (); } #ifndef __ASSUME_TIME64_SYSCALLS <32-bit fallback syscall> #endif return r; On configuration with default 64-bit time_t these optimization should be optimized away by the compiler resulting in no overhead. --- sysdeps/unix/sysv/linux/Makefile | 3 +- sysdeps/unix/sysv/linux/time64-support.c | 23 ++++++++ sysdeps/unix/sysv/linux/time64-support.h | 70 ++++++++++++++++++++++++ 3 files changed, 95 insertions(+), 1 deletion(-) create mode 100644 sysdeps/unix/sysv/linux/time64-support.c create mode 100644 sysdeps/unix/sysv/linux/time64-support.h diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile index 1932ccf7df..75c60a58f3 100644 --- a/sysdeps/unix/sysv/linux/Makefile +++ b/sysdeps/unix/sysv/linux/Makefile @@ -60,7 +60,8 @@ sysdep_routines += adjtimex clone umount umount2 readahead sysctl \ personality epoll_wait tee vmsplice splice \ open_by_handle_at mlock2 pkey_mprotect pkey_set pkey_get \ timerfd_gettime timerfd_settime prctl \ - process_vm_readv process_vm_writev clock_adjtime + process_vm_readv process_vm_writev clock_adjtime \ + time64-support CFLAGS-gethostid.c = -fexceptions CFLAGS-tee.c = -fexceptions -fasynchronous-unwind-tables diff --git a/sysdeps/unix/sysv/linux/time64-support.c b/sysdeps/unix/sysv/linux/time64-support.c new file mode 100644 index 0000000000..9f03c9adda --- /dev/null +++ b/sysdeps/unix/sysv/linux/time64-support.c @@ -0,0 +1,23 @@ +/* Auxiliary definitions for 64-bit time_t support. + Copyright (C) 2020 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 + . */ + +#include + +#ifndef __ASSUME_TIME64_SYSCALLS +int __time64_support = 1; +#endif diff --git a/sysdeps/unix/sysv/linux/time64-support.h b/sysdeps/unix/sysv/linux/time64-support.h new file mode 100644 index 0000000000..a997042fea --- /dev/null +++ b/sysdeps/unix/sysv/linux/time64-support.h @@ -0,0 +1,70 @@ +/* Auxiliary definitions for 64-bit time_t support. + Copyright (C) 2020 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 + . */ + +#include +#include + +/* These helper functions are used to optimize the 64-bit time_t support on + configurations that requires support for 32-bit time_t fallback + (!__ASSUME_TIME64_SYSCALLS). The idea is once the kernel advertises that + it does not have 64-bit time_t support, glibc will stop to try issue the + 64-bit time_t syscall altogether. + + For instance: + + #ifndef __NR_symbol_time64 + # define __NR_symbol_time64 __NR_symbol + #endif + int r; + if (supports_time64 ()) + { + r = INLINE_SYSCALL_CALL (symbol, ...); + if (r == 0 || errno != ENOSYS) + return r; + + mark_time64_unsupported (); + } + #ifndef __ASSUME_TIME64_SYSCALLS + <32-bit fallback syscall> + #endif + return r; + + On configuration with default 64-bit time_t these optimization should be + optimized away by the compiler resulting in no overhead. */ + +#ifndef __ASSUME_TIME64_SYSCALLS +extern int __time64_support attribute_hidden; +#endif + +static inline bool +supports_time64 (void) +{ +#ifdef __ASSUME_TIME64_SYSCALLS + return true; +#else + return atomic_load_relaxed (&__time64_support) != 0; +#endif +} + +static inline void +mark_time64_unsupported (void) +{ +#ifndef __ASSUME_TIME64_SYSCALLS + atomic_store_relaxed (&__time64_support, 0); +#endif +}