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atomicio: provide atomic read and write functions.

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These functions keep trying to read and write until all data has been
transferred, or an error occurrs.  In the case where an end of file
hasn't been reached, but all of the bytes have not been read/written,
try again.  On EINTR, try again.
This commit is contained in:
Nathan Binkert 2008-09-19 09:42:31 -07:00
parent af9c5e05f7
commit ce3d8c2b03
5 changed files with 157 additions and 27 deletions
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1
src/base/SConscript
View file

@ -31,6 +31,7 @@
Import('*')
Source('annotate.cc')
Source('atomicio.cc')
Source('bigint.cc')
Source('circlebuf.cc')
Source('cprintf.cc')

92
src/base/atomicio.cc Normal file
View file

@ -0,0 +1,92 @@
/*
* Copyright (c) 2008 The Hewlett-Packard Development Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Nathan Binkert
*/
#include <cerrno>
#include <cstdio>
#include "base/atomicio.hh"
ssize_t
atomic_read(int fd, void *s, size_t n)
{
char *p = reinterpret_cast<char *>(s);
ssize_t pos = 0;
// Keep reading until we've gotten all of the data.
while (n > pos) {
ssize_t result = read(fd, p + pos, n - pos);
// We didn't get any more data, so we should probably punt,
// otherwise we'd just keep spinning
if (result == 0)
break;
// If there was an error, try again on EINTR/EAGAIN, pass the
// error up otherwise.
if (result == -1) {
if (errno == EINTR || errno == EAGAIN)
continue;
return result;
}
pos += result;
}
return pos;
}
ssize_t
atomic_write(int fd, const void *s, size_t n)
{
const char *p = reinterpret_cast<const char *>(s);
ssize_t pos = 0;
// Keep writing until we've written all of the data
while (n > pos) {
ssize_t result = write(fd, p + pos, n - pos);
// We didn't manage to write anything this time, so we should
// probably punt, otherwise we'd just keep spinning
if (result == 0)
break;
// If there was an error, try again on EINTR/EAGAIN, pass the
// error up otherwise.
if (result == -1) {
if (errno == EINTR || errno == EAGAIN)
continue;
return result;
}
pos += result;
}
return pos;
}

44
src/base/atomicio.hh Normal file
View file

@ -0,0 +1,44 @@
/*
* Copyright (c) 2008 The Hewlett-Packard Development Company
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Nathan Binkert
*/
#ifndef __BASE_ATOMICIO_HH__
#define __BASE_ATOMICIO_HH__
#include <unistd.h>
// These functions keep reading/writing, if possible, until all data
// has been transferred. Basically, try again when there's no error,
// but there is data left also retry on EINTR.
// This function blocks until it is done.
ssize_t atomic_read(int fd, void *s, size_t n);
ssize_t atomic_write(int fd, const void *s, size_t n);
#endif // __BASE_ATOMICIO_HH__

29
src/base/circlebuf.cc
View file

@ -29,12 +29,11 @@
*/
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <string>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "base/atomicio.hh"
#include "base/circlebuf.hh"
#include "base/cprintf.hh"
#include "base/intmath.hh"
@ -59,8 +58,8 @@ CircleBuf::dump()
cprintf("start = %10d, stop = %10d, buflen = %10d\n",
_start, _stop, _buflen);
fflush(stdout);
::write(STDOUT_FILENO, _buf, _buflen);
::write(STDOUT_FILENO, "<\n", 2);
atomic_write(STDOUT_FILENO, _buf, _buflen);
atomic_write(STDOUT_FILENO, "<\n", 2);
}
void
@ -106,19 +105,19 @@ CircleBuf::read(int fd, int len)
if (_stop > _start) {
len = min(len, _stop - _start);
::write(fd, _buf + _start, len);
atomic_write(fd, _buf + _start, len);
_start += len;
}
else {
int endlen = _buflen - _start;
if (endlen > len) {
::write(fd, _buf + _start, len);
atomic_write(fd, _buf + _start, len);
_start += len;
}
else {
::write(fd, _buf + _start, endlen);
atomic_write(fd, _buf + _start, endlen);
_start = min(len - endlen, _stop);
::write(fd, _buf, _start);
atomic_write(fd, _buf, _start);
}
}
}
@ -129,11 +128,11 @@ CircleBuf::read(int fd)
_size = 0;
if (_stop > _start) {
::write(fd, _buf + _start, _stop - _start);
atomic_write(fd, _buf + _start, _stop - _start);
}
else {
::write(fd, _buf + _start, _buflen - _start);
::write(fd, _buf, _stop);
atomic_write(fd, _buf + _start, _buflen - _start);
atomic_write(fd, _buf, _stop);
}
_start = _stop;
@ -159,9 +158,9 @@ void
CircleBuf::readall(int fd)
{
if (_rollover)
::write(fd, _buf + _stop, _buflen - _stop);
atomic_write(fd, _buf + _stop, _buflen - _stop);
::write(fd, _buf, _stop);
atomic_write(fd, _buf, _stop);
_start = _stop;
}

18
src/dev/terminal.cc
View file

@ -35,16 +35,17 @@
#include <sys/ioctl.h>
#include <sys/termios.h>
#include <sys/types.h>
#include <errno.h>
#include <poll.h>
#include <unistd.h>
#include <cctype>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include "base/atomicio.hh"
#include "base/misc.hh"
#include "base/output.hh"
#include "base/socket.hh"
@ -156,7 +157,7 @@ Terminal::accept()
int fd = listener.accept(true);
if (data_fd != -1) {
char message[] = "terminal already attached!\n";
::write(fd, message, sizeof(message));
atomic_write(fd, message, sizeof(message));
::close(fd);
return;
}
@ -238,16 +239,9 @@ Terminal::write(const uint8_t *buf, size_t len)
if (data_fd < 0)
panic("Terminal not properly attached.\n");
size_t ret;
for (;;) {
ret = ::write(data_fd, buf, len);
if (ret >= 0)
break;
if (errno != EINTR)
detach();
}
ssize_t ret = atomic_write(data_fd, buf, len);
if (ret < len)
detach();
return ret;
}