c485cdb024
The locking can fail in a couple of ways:
- A concurrent fread from an unbuffered or line-buffered file flushes
the output of other line-buffered files, and if _fwalk locks every
file, then the fread blocks until other file reads have completed.
- __sfp can initialize a file lock while _fwalk is locking/unlocking it.
For now, revert to the behavior Bionic had in previous releases. This
commit reverts the file locking parts of commit
468efc80da.
Bug: http://b/131251441
Bug: http://b/130189834
Test: bionic unit tests
Change-Id: I9e20b9cd8ccd14e7962f7308e174f08af72b56c6
124 lines
3.6 KiB
C
124 lines
3.6 KiB
C
/* $OpenBSD: refill.c,v 1.11 2009/11/09 00:18:27 kurt Exp $ */
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/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "local.h"
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static int
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lflush(FILE *fp)
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{
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if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
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return (__sflush_locked(fp)); /* ignored... */
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return (0);
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}
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/*
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* Refill a stdio buffer.
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* Return EOF on eof or error, 0 otherwise.
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*/
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int
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__srefill(FILE *fp)
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{
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fp->_r = 0; /* largely a convenience for callers */
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#if !defined(__BIONIC__)
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/* SysV does not make this test; take it out for compatibility */
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if (fp->_flags & __SEOF)
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return (EOF);
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#endif
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/* if not already reading, have to be reading and writing */
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if ((fp->_flags & __SRD) == 0) {
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if ((fp->_flags & __SRW) == 0) {
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errno = EBADF;
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fp->_flags |= __SERR;
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return (EOF);
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}
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/* switch to reading */
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if (fp->_flags & __SWR) {
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if (__sflush(fp))
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return (EOF);
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fp->_flags &= ~__SWR;
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fp->_w = 0;
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fp->_lbfsize = 0;
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}
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fp->_flags |= __SRD;
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} else {
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/*
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* We were reading. If there is an ungetc buffer,
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* we must have been reading from that. Drop it,
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* restoring the previous buffer (if any). If there
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* is anything in that buffer, return.
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*/
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if (HASUB(fp)) {
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FREEUB(fp);
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if ((fp->_r = fp->_ur) != 0) {
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fp->_p = fp->_up;
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return (0);
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}
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}
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}
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if (fp->_bf._base == NULL)
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__smakebuf(fp);
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/*
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* Before reading from a line buffered or unbuffered file,
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* flush all line buffered output files, per the ANSI C
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* standard.
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*/
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if (fp->_flags & (__SLBF|__SNBF)) {
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/* Ignore this file in _fwalk to avoid potential deadlock. */
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fp->_flags |= __SIGN;
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(void) _fwalk(lflush);
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fp->_flags &= ~__SIGN;
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/* Now flush this file without locking it. */
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if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
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__sflush(fp);
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}
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fp->_p = fp->_bf._base;
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fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
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if (fp->_r <= 0) {
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if (fp->_r == 0)
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fp->_flags |= __SEOF;
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else {
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fp->_r = 0;
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fp->_flags |= __SERR;
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}
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return (EOF);
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}
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return (0);
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}
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