moss.ipc
Class MSemaphore

java.lang.Object
  moss.ipc.MSemaphore

public class MSemaphore
extends java.lang.Object

this class implements a "semaphore". Operations are performed based on changing the semaphore's value arbitrarily, not strictly `wait' (-1) and `signal' (+1). However, wait() and signal() methods are still provided, for bits of the kernel that want to use them like that.

Field Summary

static int	SEMOP_CREATE create a semaphore
static int	SEMOP_REMOVE remove a semaphore
static int	SEMOP_SET set (adjust) a semaphore's value

Constructor Summary

MSemaphore()

Method Summary

static void	finalinit() this is called to perform any final initialisation, in the context of the init-task.
static void	init_semaphore() this initialises the semaphore handling class
static int	semcreate(int key, int value) creates a new semaphore
static int	semremove(int key) removes a semaphore.
static int	semset(MProcess current, int key, int value) changes a semaphore's value

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SEMOP_CREATE

public static final int SEMOP_CREATE

create a semaphore

See Also:

Constant Field Values

SEMOP_SET

public static final int SEMOP_SET

set (adjust) a semaphore's value

See Also:

Constant Field Values

SEMOP_REMOVE

public static final int SEMOP_REMOVE

remove a semaphore

See Also:

Constant Field Values

Constructor Detail

MSemaphore

public MSemaphore()

Method Detail

init_semaphore

public static void init_semaphore()

this initialises the semaphore handling class

finalinit

public static void finalinit()

this is called to perform any final initialisation, in the context of the init-task.

semcreate

public static int semcreate(int key,
                            int value)

creates a new semaphore

Parameters:

key - semaphore key

value - initial value of the semaphore. If < 0, the method blocks.

Returns:

0 on success, or < 0 indicating error (key already exists)

semset

public static int semset(MProcess current,
                         int key,
                         int value)

changes a semaphore's value

Parameters:

key - semaphore key

value - change semaphore value by this (+ve or -ve)

Returns:

0 on success, or < 0 indicating error

semremove

public static int semremove(int key)

removes a semaphore. Blocked processes are woken up -- they return with ENOENT

Parameters:

key - semaphore key

Returns:

0 on success, or < 0 indicating error