com.oracle.svm.core.locks

Class VMMutex

java.lang.Object

com.oracle.svm.core.locks.VMMutex

All Implemented Interfaces:

AutoCloseable

public class VMMutex
extends Object
implements AutoCloseable

A mutex that has minimal requirements on Java code. The implementation does not perform memory allocation, exception unwinding, or other complicated operations. This allows it to be used in early startup and shutdown phases of the VM, as well as to coordinate garbage collection. Higher-level code that does not have these restrictions should use regular locks from the JDK instead, i.e., implementations of Lock. It is not possible to allocate new VM mutexes at run time. All VM mutexes must be allocated during image generation. They are initialized during startup of the VM, i.e., every VM mutex consumes resources and contributes to VM startup time. This class is almost an abstract base class for VMMutex. Sub-classes replace instances of VMMutex with platform-specific implementations.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	VMMutex.TestingBackdoor

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	locked For assertions about locking.

Constructor Summary

Constructors

Constructor and Description
VMMutex()

Method Summary

Modifier and Type	Method and Description
void	assertIsLocked(String message)
void	assertIsNotLocked(String message)
void	close() Releases the lock when locking using a try-with-resource statement.
void	guaranteeIsLocked(String message)
VMMutex	lock() Acquires the lock, with thread status transitions, blocking until the lock is available.
VMMutex	lockNoTransition() Like VMMutex.lock(), but without a thread status transitions.
void	unlock() Releases the lock.
void	unlockWithoutChecks() Releases the lock, without checking the result.
void	warnIfNotLocked(String message)

Methods inherited from class java.lang.Object

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

Field Detail

locked

protected boolean locked

For assertions about locking.

Constructor Detail

VMMutex

public VMMutex()

Method Detail

lock

public VMMutex lock()

Acquires the lock, with thread status transitions, blocking until the lock is available. Recursive locking is not allowed. Returns "this" for use in a try-with-resources statement.

lockNoTransition

public VMMutex lockNoTransition()

Like VMMutex.lock(), but without a thread status transitions. E.g., for locking before everything is set up to track transitions.

unlock

public void unlock()

Releases the lock.

unlockWithoutChecks

public void unlockWithoutChecks()

Releases the lock, without checking the result.

close

public final void close()

Releases the lock when locking using a try-with-resource statement.

This is not annotated with Uninterruptible because using try-with-resources implicitly calls Throwable.addSuppressed(Throwable), which I can not annotate.

Specified by:

close in interface AutoCloseable

assertIsLocked

public final void assertIsLocked(String message)

assertIsNotLocked

public final void assertIsNotLocked(String message)

warnIfNotLocked

public final void warnIfNotLocked(String message)

guaranteeIsLocked

public final void guaranteeIsLocked(String message)