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/*
* Worldvisions Weaver Software:
* Copyright (C) 1997-2002 Net Integration Technologies, Inc.
*
* Some handy functions to create/remove /var/lock lockfiles.
*/
#include "wvlockdev.h"
#include "wvfile.h"
#include "strutils.h"
#include <signal.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
WvLockDev::WvLockDev(WvString _devicename)
: devicename(_devicename)
{
const char *p = strrchr(devicename, '/');
if (p)
p++;
else
p = devicename;
lock_count = 0;
filename = WvString("/var/lock/LCK..%s", p);
}
WvLockDev::~WvLockDev()
{
if (lock_count)
{
lock_count = 1;
unlock();
}
}
#if USE_LOCKDEV /* use the liblockdev.a locking routines */
#include <lockdev.h>
bool WvLockDev::lock()
{
if (lock_count)
{
lock_count++;
return true;
}
if (dev_lock(devicename))
return false;
lock_count++;
return true;
}
void WvLockDev::unlock()
{
if (!lock_count) return;
if (!--lock_count)
dev_unlock(devicename, getpid());
}
#else /* !USE_LOCKDEV -- implement our own locking routines */
// note: this function uses the O_EXCL flag to open(), and thus assumes
// that /var/lock is not an NFS-mounted drive (according to the open() man
// page, you need to follow a special procedure to ensure successful NFS
// locking)
//
// Actually there may be other race conditions that we should look into.
bool WvLockDev::lock()
{
pid_t pid;
if (lock_count)
{
lock_count++;
return true;
}
WvFile fd(filename, O_RDWR | O_EXCL | O_CREAT, 0644);
if (fd.isok())
{
// We made a lock file...
fd.print("%10s\n", getpid());
}
else if (fd.geterr() == EEXIST)
{
char *inbuf;
// Lock file is already there! Check for staleness...
sleep(1); // preventing race condition...
fd.open(filename, O_RDONLY);
//fprintf(stderr, "ok: %d\n", fd.isok());
inbuf = trim_string(fd.getline(-1));
//fprintf(stderr, "getline: '%s'\n", inbuf);
if (inbuf)
pid = atoi(inbuf);
else
pid = 0;
//fprintf(stderr, "pid: '%d'\n", pid);
if (pid && pid != -1 && kill(pid, 0) == -1 && errno == ESRCH)
{
// we can create a lockfile now
fd.close();
if (unlink(filename))
return false; // cannot remove lockfile
fd.open(filename, O_RDWR | O_EXCL | O_CREAT, 0644);
fd.print("%10s\n", getpid());
}
else
return false; // device already locked
}
else // some other unexpected error
return false;
lock_count++;
return true;
}
void WvLockDev::unlock()
{
if (!lock_count) return;
if (!--lock_count)
unlink(filename);
}
#endif /* !USE_LOCKDEV */
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