org.jikesrvm.scheduler

Class RVMThread.BlockAdapter

java.lang.Object

org.jikesrvm.scheduler.RVMThread.BlockAdapter

Direct Known Subclasses:

RVMThread.GCBlockAdapter, RVMThread.HandshakeBlockAdapter, RVMThread.SuspendBlockAdapter, RVMThread.ThreadStackTraceBlockAdapter

Enclosing class:

RVMThread

public abstract static class RVMThread.BlockAdapter
extends Object

A block adapter specifies the reason for blocking or unblocking a thread. A thread remains blocked so long as any of the block adapters say that it should be blocked. Block adapters are statically allocated, and store their state in instance fields of RVMThread.

Constructor Summary

Constructors

Constructor and Description
BlockAdapter()

Method Summary

Modifier and Type	Method and Description
(package private) abstract void	clearBlockRequest(RVMThread t) Clears any blocking requests for the thread.
(package private) abstract boolean	hasBlockRequest(RVMThread t)
(package private) abstract boolean	hasBlockRequest(RVMThread t, int token)
(package private) abstract boolean	isBlocked(RVMThread t)
(package private) abstract int	requestBlock(RVMThread t) Requests that the thread block, for this block adapter, at its earliest convenience.
(package private) abstract void	setBlocked(RVMThread t, boolean value) Specifies that the thread is either blocked (value == true) or not blocked (value == false) for this block adapter.

Methods inherited from class java.lang.Object

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

Constructor Detail

BlockAdapter

public BlockAdapter()

Method Detail

isBlocked

abstract boolean isBlocked(RVMThread t)

Parameters:

t - a thread

Returns:

whether the given thread should be blocked for this block adapter. If true, the thread is guaranteed to block.

setBlocked

abstract void setBlocked(RVMThread t,
                         boolean value)

Specifies that the thread is either blocked (value == true) or not blocked (value == false) for this block adapter. This call indicates a statement of fact by the thread itself - it's used either to acknowledge a block request (see hasBlockRequest(RVMThread) below) or to respond to a request to unblock.

Parameters:

t - the thread

value - the new value of the status for blocking as described above

requestBlock

abstract int requestBlock(RVMThread t)

Requests that the thread block, for this block adapter, at its earliest convenience.

Called from RVMThread.block() and associated methods. Some block adapters allow for multiple requests to block; in that case this will return a "token" that can be passed to hasBlockRequest() to check, not only whether there is a block request, but whether that block request is still associated with a particular call to requestBlock(). This is used to prevent a suspend() call from stalling due to a concurrent resume() and second suspend(). Note that most block adapers don't care about this scenario, and will just return 0 (or some other meaningless number) here.

Parameters:

t - the thread that needs to block

Returns:

a token as described above

hasBlockRequest

abstract boolean hasBlockRequest(RVMThread t)

Parameters:

t - the thread

Returns:

whether the thread has a request to block for this block adapter

hasBlockRequest

abstract boolean hasBlockRequest(RVMThread t,
                                 int token)

Parameters:

t - the thread to check for block requests

token - a token, see requestBlock(RVMThread)

Returns:

whether the thread has a block request associated with the given requestBlock() call

clearBlockRequest

abstract void clearBlockRequest(RVMThread t)

Clears any blocking requests for the thread.

Parameters:

t - thread whose block requests will be cleared