jdk.dio.watchdog

Interface WindowedWatchdogTimer

All Superinterfaces:

java.lang.AutoCloseable, java.nio.channels.Channel, java.io.Closeable, Device<WatchdogTimer>, WatchdogTimer

public interface WindowedWatchdogTimer
extends WatchdogTimer

The WindowedWatchdogTimer interface provides methods for controlling a watchdog timer that can be used to force the device to reboot (or depending on the platform, the Java Virtual Machine to restart).

The windowed watchdog timer must be refreshed within an open time window. If the watchdog is refreshed too soon - during the closed window - or if it is refreshed too late - after the watchdog timeout has expired - the device will be rebooted (or the JVM restarted).

A WindowedWatchdogTimer instance may represent a virtual windowed watchdog timer. If the device has a single physical windowed watchdog timer, all of the virtual watchdog timers are mapped onto this one physical watchdog timer. It gets set with a refresh window starting when the virtual windowed watchdog with the longest closed window delay is scheduled to end and ending when the virtual windowed watchdog with the earliest timeout is scheduled to expire. The corresponding watchdog timer device is therefore shared and several applications can concurrently acquire the same watchdog timer device.

Since:

1.0

Field Summary

Fields inherited from interface jdk.dio.Device

BIG_ENDIAN, LITTLE_ENDIAN, MIXED_ENDIAN

Method Summary

Methods

Modifier and Type	Method and Description
long	getClosedWindowTimeout() Get the current closed window delay for the watchdog timer.
void	start(long timeout) Starts the watchdog timer with the specified timeout and with a closed window delay set to 0.
void	start(long closedWindowDelay, long timeout) Starts the windowed watchdog timer with the specified closed window delay and timeout.

Methods inherited from interface jdk.dio.watchdog.WatchdogTimer

causedLastReboot, getMaxTimeout, getTimeout, refresh, stop

Methods inherited from interface jdk.dio.Device

close, getByteOrder, getDescriptor, isOpen, tryLock, unlock

Method Detail

getClosedWindowTimeout

long getClosedWindowTimeout()
                            throws java.io.IOException,
                                   ClosedDeviceException

Get the current closed window delay for the watchdog timer. If the timer is disabled 0 is returned. Additionally, the value returned may differ from the previously set value as it may have been adjusted to account for the timer resolution or discrete time interval values supported by the underlying platform or driver.

Returns:

the delay (in milliseconds) until the watchdog timer can be refreshed; or 0 if the timer is disabled.

Throws:

java.io.IOException - if some other I/O error occurs.

ClosedDeviceException - if the device has been closed.

See Also:

start(long, long)

start

void start(long timeout)
           throws java.io.IOException,
                  ClosedDeviceException

Starts the watchdog timer with the specified timeout and with a closed window delay set to 0. If the watchdog timer is not refreshed by a call to refresh prior to the watchdog timing out, the device will be rebooted (or the JVM restarted).

The timeout is expressed in milliseconds; if the underlying platform or driver does not support a millisecond resolution or does not support the requested time interval value then timeout will be rounded up to accommodate the supported timer resolution or respectively aligned to the closest greater supported discrete time interval value. The resulting, actual timeout can be retrieved by a call to getTimeout.

Calling this method twice is equivalent to stopping the timer as per a call to stop and starting it again with the new specified timeout and with a closed window delay set to 0.

Specified by:

start in interface WatchdogTimer

Parameters:

timeout - the time interval (in milliseconds) until watchdog times out.

Throws:

java.io.IOException - if some other I/O error occurs.

java.lang.IllegalArgumentException - if timeout is not greater than 0 or if timeout is greater than the maximum supported timeout as returned buy WatchdogTimer.getMaxTimeout().

ClosedDeviceException - if the device has been closed.

start

void start(long closedWindowDelay,
         long timeout)
           throws java.io.IOException,
                  ClosedDeviceException

Starts the windowed watchdog timer with the specified closed window delay and timeout. If the refresh method is called too soon, that is within the closed window delay, or too late, that is not called prior to the watchdog timing out, the device will be rebooted (or the JVM restarted).

The timeout is expressed in milliseconds; if the underlying platform or driver does not support a millisecond resolution or does not support the requested time interval value then timeout will be rounded up to accommodate the supported timer resolution or respectively aligned to the closest greater supported discrete time interval value. The resulting, actual timeout can be retrieved by a call to getTimeout.
Similarly, the closed window delay is expressed in milliseconds; if the underlying platform or driver does not support a millisecond resolution or does not support the requested time interval value then closedWindowDelay will be rounded down to accommodate the supported timer resolution or respectively aligned to the closest lower supported discrete time interval value. The resulting, actual timeout can be retrieved by a call to getClosedWindowTimeout.

Calling this method twice is equivalent to stopping the timer as per a call to stop and starting it again with the new specified closed window delay and timeout.

Parameters:

closedWindowDelay - the delay (in milliseconds) until the watchdog timer can be refreshed.

timeout - the time interval (in milliseconds) until watchdog times out.

Throws:

java.lang.IllegalArgumentException - if timeout is not greater than 0 or if timeout is greater than the maximum supported timeout as returned by WatchdogTimer.getMaxTimeout(); or if closedWindowDelay is negative or closedWindowDelay is greater than or equal to timeout.

java.io.IOException - if some other I/O error occurs.

ClosedDeviceException - if the device has been closed.