From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8830 invoked by alias); 28 Apr 2014 14:50:34 -0000 Mailing-List: contact libc-ports-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: libc-ports-owner@sourceware.org Received: (qmail 8816 invoked by uid 89); 28 Apr 2014 14:50:33 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.1 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-qg0-f52.google.com Received: from mail-qg0-f52.google.com (HELO mail-qg0-f52.google.com) (209.85.192.52) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-SHA encrypted) ESMTPS; Mon, 28 Apr 2014 14:50:31 +0000 Received: by mail-qg0-f52.google.com with SMTP id j5so6979312qga.39 for ; Mon, 28 Apr 2014 07:50:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:date:message-id:subject:from:to :content-type; bh=INXZrcPvap3952+VQ8pV0vDLw+hkN2niL/ypuD64Em4=; b=HLZZPT8VVx9ZH5VbG4hs8KUkj7F5fUt0iUGT6ilKqCpTpcUtLX4LqDklqEOUiyeIYc eLhpJrxKiayKSGiTp2Q7vvYtTUV0SSxfILMo0ZRCC1qjCiibGhqx4uKkG0RjWxxd+sNx LWk7wq4DKmoIw7ZTaSbS1MtttrDl1zQEryrm6QTSV1kBIYd22ZHzRXWmrax0+lRufoT5 VO9JqrcPh8jRWVDD0DXX60Ac0C19bhSlyoy57Ez0v+QnWKUea1azX83luNz1nb7abfYk P/bKzoNGTh+dgysX1znbsPz3akhuWYeE5YoSc0Ckc5vQuu6NxfTkMezfCsLhhOoUxAQn xcWg== X-Gm-Message-State: ALoCoQk6QwSk5nvzjULmlZ66tckxACDlbpmY4xlIClHopqPtEVtwzyCTJAmHGad2gP9KfXKBBHwf MIME-Version: 1.0 X-Received: by 10.140.43.70 with SMTP id d64mr32406752qga.11.1398696629445; Mon, 28 Apr 2014 07:50:29 -0700 (PDT) Received: by 10.96.152.200 with HTTP; Mon, 28 Apr 2014 07:50:29 -0700 (PDT) Date: Mon, 28 Apr 2014 14:50:00 -0000 Message-ID: Subject: [PATCH] Remove arm lowlevellock.c From: Bernie Ogden To: libc-ports@sourceware.org Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2014-04/txt/msg00002.txt.bz2 lowlevellock.c for arm differs from the generic lowlevellock.c only in insignificant ways, so can be removed. Happily, this fixes BZ 15119 (unnecessary busy loop in __lll_timedlock_wait on arm). The notable differences between the arm and generic implementations are: 1) arm __lll_timedlock_wait has a fast path out if futex has been set to 0 between since the function was called. This seems unlikely to happen very often, so it seems at worst harmless to lose this fast path. 2) Some function in arm's lowlevellock.c set futex to 2 if it was 1. The generic version always sets the futex to 2. As futex can only be 0, 1 or 2 on entry into these functions, the behaviour is equivalent. (If the futex manages to be 0 on entry then we've just lost another unlikely fast path out.) There are no test suite regressions. Note that hppa and sparc also have their own lowlevellock.c. I believe hppa can also be removed, so I'll send a separate patch for that shortly. sparc's seems to be genuinely needed as it uses a different locking structure. Also note that the analysis at https://sourceware.org/ml/libc-ports/2013-02/msg00021.html indicates a further locking performance bug to fix - I've got a partial patch for that which I can submit once I've finished testing. 2014-04-24 Bernard Ogden [BZ #15119] * sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.c: Remove file. diff --git a/sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.c b/sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.c deleted file mode 100644 index 9603d7b..0000000 --- a/sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.c +++ /dev/null @@ -1,132 +0,0 @@ -/* low level locking for pthread library. Generic futex-using version. - Copyright (C) 2003-2014 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 -#include -#include - -void -__lll_lock_wait_private (int *futex) -{ - do - { - int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1); - if (oldval != 0) - lll_futex_wait (futex, 2, LLL_PRIVATE); - } - while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0); -} - - -/* These functions don't get included in libc.so */ -#ifdef IS_IN_libpthread -void -__lll_lock_wait (int *futex, int private) -{ - do - { - int oldval = atomic_compare_and_exchange_val_acq (futex, 2, 1); - if (oldval != 0) - lll_futex_wait (futex, 2, private); - } - while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0); -} - - -int -__lll_timedlock_wait (int *futex, const struct timespec *abstime, int private) -{ - struct timespec rt; - - /* Reject invalid timeouts. */ - if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) - return EINVAL; - - /* Upgrade the lock. */ - if (atomic_exchange_acq (futex, 2) == 0) - return 0; - - do - { - struct timeval tv; - - /* Get the current time. */ - (void) __gettimeofday (&tv, NULL); - - /* Compute relative timeout. */ - rt.tv_sec = abstime->tv_sec - tv.tv_sec; - rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000; - if (rt.tv_nsec < 0) - { - rt.tv_nsec += 1000000000; - --rt.tv_sec; - } - - /* Already timed out? */ - if (rt.tv_sec < 0) - return ETIMEDOUT; - - // XYZ: Lost the lock to check whether it was private. - lll_futex_timed_wait (futex, 2, &rt, private); - } - while (atomic_compare_and_exchange_bool_acq (futex, 2, 0) != 0); - - return 0; -} - - -int -__lll_timedwait_tid (int *tidp, const struct timespec *abstime) -{ - int tid; - - if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) - return EINVAL; - - /* Repeat until thread terminated. */ - while ((tid = *tidp) != 0) - { - struct timeval tv; - struct timespec rt; - - /* Get the current time. */ - (void) __gettimeofday (&tv, NULL); - - /* Compute relative timeout. */ - rt.tv_sec = abstime->tv_sec - tv.tv_sec; - rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000; - if (rt.tv_nsec < 0) - { - rt.tv_nsec += 1000000000; - --rt.tv_sec; - } - - /* Already timed out? */ - if (rt.tv_sec < 0) - return ETIMEDOUT; - - /* Wait until thread terminates. */ - // XYZ: Lost the lock to check whether it was private. - if (lll_futex_timed_wait (tidp, tid, &rt, LLL_SHARED) == -ETIMEDOUT) - return ETIMEDOUT; - } - - return 0; -} -#endif