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#
# Copyright 2018 Ettus Research, a National Instruments Company
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
"""
systemd watchdog control module
"""
import os
import time
import threading
from systemd import daemon
MPM_WATCHDOG_DEFAULT_TIMEOUT = 30
# How often per watchdog interval we send a ping
MPM_WATCHDOG_TIMEOUT_FRAC = 3.0
def has_watchdog():
"""Check if the system has a watchdog checking on us.
We do this by checking on a set value for WATCHDOG_USEC.
"""
return bool(os.environ.get('WATCHDOG_USEC', False))
def transfer_control(pid):
"""
Transfer control of watchdog notifications to new PID.
"""
daemon.notify("MAINPID={:d}".format(int(pid)))
def _watchdog_task(shared_state, log):
"""
Continuously ping the watchdog to tell him that we're still alive.
This will keep running until the parent thread dies, or
shared_state.system_ready gets set to False by someone.
"""
watchdog_timeout = \
float(os.environ.get(
'WATCHDOG_USEC',
MPM_WATCHDOG_DEFAULT_TIMEOUT
)) / 1e6
watchdog_interval = watchdog_timeout / MPM_WATCHDOG_TIMEOUT_FRAC
daemon.notify("READY=1")
log.debug("Watchdog primed, going into watchdog loop (Interval: %s s)",
watchdog_interval)
while shared_state.system_ready.value:
# Sleep first, then ping, that avoids the case where transfer_control()
# is not yet complete before we call this for the first time, which
# would lead in error messages popping up in the systemd journal.
time.sleep(watchdog_interval)
log.trace("Pinging watchdog....")
daemon.notify("WATCHDOG=1")
log.error("Terminating watchdog thread!")
return
def spawn_watchdog_task(shared_state, log):
"""Spawn and return watchdog thread.
Creates a daemonic thread, because we don't want the watchdog task to
outlive the main thread.
"""
task = threading.Thread(
target=_watchdog_task,
args=[shared_state, log],
name="MPMWatchdogTask",
daemon=True,
)
task.start()
return task
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