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/* Copyright © 2005-2013 Roger Leigh <rleigh@debian.org>
*
* schroot is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* schroot 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see
* <http://www.gnu.org/licenses/>.
*
*********************************************************************/
#include <config.h>
#include <sbuild/lock.h>
#include <sbuild/log.h>
#include <sbuild/feature.h>
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <unistd.h>
#include <boost/format.hpp>
using boost::format;
namespace sbuild
{
template<>
error<lock::error_code>::map_type
error<lock::error_code>::error_strings =
{
{lock::TIMEOUT_HANDLER, N_("Failed to set timeout handler")},
{lock::TIMEOUT_SET, N_("Failed to set timeout")},
{lock::TIMEOUT_CANCEL, N_("Failed to cancel timeout")},
{lock::LOCK, N_("Failed to lock file")},
{lock::UNLOCK, N_("Failed to unlock file")},
// TRANSLATORS: %4% = time in seconds
{lock::LOCK_TIMEOUT, N_("Failed to lock file (timed out after %4% seconds)")},
// TRANSLATORS: %4% = time in seconds
{lock::UNLOCK_TIMEOUT, N_("Failed to unlock file (timed out after %4% seconds)")},
{lock::DEVICE_LOCK, N_("Failed to lock device")},
// TRANSLATORS: %4% = time in seconds
// TRANSLATORS: %5% = integer process ID
{lock::DEVICE_LOCK_TIMEOUT, N_("Failed to lock device (timed out after %4% seconds; lock held by PID %5%)")},
{lock::DEVICE_TEST, N_("Failed to test device lock")},
{lock::DEVICE_UNLOCK, N_("Failed to unlock device")},
// TRANSLATORS: %4% = time in seconds
// TRANSLATORS: %5% = integer process ID
{lock::DEVICE_UNLOCK_TIMEOUT, N_("Failed to unlock device (timed out after %4% seconds; lock held by PID %5%)")}
};
namespace
{
/**
* Handle the SIGALRM signal. This exists so that system calls get
* interrupted.
*
* @param ignore the signal number.
*/
void
alarm_handler (int ignore)
{
}
}
lock::lock ():
saved_signals()
{
}
lock::~lock ()
{
}
void
lock::set_alarm ()
{
struct sigaction new_sa;
sigemptyset(&new_sa.sa_mask);
new_sa.sa_flags = 0;
new_sa.sa_handler = alarm_handler;
if (sigaction(SIGALRM, &new_sa, &this->saved_signals) != 0)
throw error(TIMEOUT_HANDLER, strerror(errno));
}
void
lock::clear_alarm ()
{
/* Restore original handler */
sigaction (SIGALRM, &this->saved_signals, 0);
}
void
lock::set_timer(const struct itimerval& timer)
{
set_alarm();
if (setitimer(ITIMER_REAL, &timer, 0) == -1)
{
clear_alarm();
throw error(TIMEOUT_SET, strerror(errno));
}
}
void
lock::unset_timer ()
{
struct itimerval disable_timer;
disable_timer.it_interval.tv_sec = disable_timer.it_interval.tv_usec = 0;
disable_timer.it_value.tv_sec = disable_timer.it_value.tv_usec = 0;
if (setitimer(ITIMER_REAL, &disable_timer, 0) == -1)
{
clear_alarm();
throw error(TIMEOUT_CANCEL, strerror(errno));
}
clear_alarm();
}
file_lock::file_lock (int fd):
lock(),
fd(fd),
locked(false)
{
}
file_lock::~file_lock ()
{
// Release a lock if held. Note that the code is duplicated from
// set_lock because we don't want to throw an exception in a
// destructor under any circumstances. Any error is logged.
if (locked)
{
struct flock read_lock;
read_lock.l_type = LOCK_NONE;
read_lock.l_whence = SEEK_SET;
read_lock.l_start = 0;
read_lock.l_len = 0; // Lock entire file
read_lock.l_pid = 0;
if (fcntl(this->fd, F_SETLK, &read_lock) == -1)
log_exception_warning(error(UNLOCK, strerror(errno)));
}
}
void
file_lock::set_lock (lock::type lock_type,
unsigned int timeout)
{
try
{
struct itimerval timeout_timer;
timeout_timer.it_interval.tv_sec = timeout_timer.it_interval.tv_usec = 0;
timeout_timer.it_value.tv_sec = timeout;
timeout_timer.it_value.tv_usec = 0;
set_timer(timeout_timer);
/* Now the signal handler and itimer are set, the function can't
return without stopping the timer and restoring the signal
handler to its original state. */
/* Wait on lock until interrupted by a signal if a timeout was set,
otherwise return immediately. */
struct flock read_lock;
read_lock.l_type = lock_type;
read_lock.l_whence = SEEK_SET;
read_lock.l_start = 0;
read_lock.l_len = 0; // Lock entire file
read_lock.l_pid = 0;
if (fcntl(this->fd,
(timeout != 0) ? F_SETLKW : F_SETLK,
&read_lock) == -1)
{
if (errno == EINTR)
throw error((lock_type == LOCK_SHARED ||
lock_type == LOCK_EXCLUSIVE)
? LOCK_TIMEOUT : UNLOCK_TIMEOUT,
timeout);
else
throw error((lock_type == LOCK_SHARED ||
lock_type == LOCK_EXCLUSIVE) ? LOCK : UNLOCK,
strerror(errno));
}
if (lock_type == LOCK_SHARED || lock_type == LOCK_EXCLUSIVE)
this->locked = true;
else
this->locked = false;
unset_timer();
}
catch (const error& e)
{
unset_timer();
throw;
}
}
void
file_lock::unset_lock ()
{
set_lock(LOCK_NONE, 0);
}
}
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