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import os
import time
from ZeekControl import config
lockCount = 0
# Return: 0 if no lock, >0 for PID of lock, or -1 on error
def _break_lock(cmdout):
from ZeekControl import execute
try:
# Check whether lock is stale.
with open(config.Config.lockfile, "r") as f:
pid = f.readline().strip()
except (OSError, IOError) as err:
cmdout.error("failed to read lock file: %s" % err)
return -1
success, output = execute.run_localcmd("%s %s" % (os.path.join(config.Config.helperdir, "check-pid"), pid))
if success and output.strip() == "running":
# Process still exists.
try:
return int(pid)
except ValueError:
return -1
cmdout.info("removing stale lock")
try:
# Break lock.
os.unlink(config.Config.lockfile)
except (OSError, IOError) as err:
cmdout.error("failed to remove lock file: %s" % err)
return -1
return 0
# Return: 0 if lock is acquired, or if failed to acquire lock return >0 for
# PID of lock, or -1 on error
def _acquire_lock(cmdout):
lockpid = -1
pid = str(os.getpid())
tmpfile = config.Config.lockfile + "." + pid
lockdir = os.path.dirname(config.Config.lockfile)
if not os.path.exists(lockdir):
cmdout.info("creating directory for lock file: %s" % lockdir)
os.makedirs(lockdir)
try:
try:
# This should be NFS-safe.
with open(tmpfile, "w") as f:
f.write("%s\n" % pid)
n = os.stat(tmpfile)[3]
os.link(tmpfile, config.Config.lockfile)
m = os.stat(tmpfile)[3]
if n == m-1:
return 0
# File is locked.
lockpid = _break_lock(cmdout)
if lockpid == 0:
return _acquire_lock(cmdout)
except OSError:
# File is already locked.
lockpid = _break_lock(cmdout)
if lockpid == 0:
return _acquire_lock(cmdout)
except IOError as e:
cmdout.error("cannot acquire lock: %s" % e)
return lockpid
finally:
try:
os.unlink(tmpfile)
except (OSError, IOError):
pass
return lockpid
def _release_lock(cmdout):
try:
os.unlink(config.Config.lockfile)
except OSError as e:
cmdout.error("cannot remove lock file: %s" % e)
def lock(cmdout, showwait=True):
global lockCount
if lockCount > 0:
# Already locked.
lockCount += 1
return True
lockpid = _acquire_lock(cmdout)
if lockpid < 0:
return False
if lockpid:
if showwait:
cmdout.info("waiting for lock (owned by PID %d) ..." % lockpid)
count = 0
while _acquire_lock(cmdout) != 0:
time.sleep(1)
count += 1
if count > 30:
return False
lockCount = 1
return True
def unlock(cmdout):
global lockCount
if lockCount == 0:
cmdout.error("mismatched lock/unlock")
return
if lockCount > 1:
# Still locked.
lockCount -= 1
return
_release_lock(cmdout)
lockCount = 0
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