org.apache.tomcat.jni
Class Lock

java.lang.Object
  org.apache.tomcat.jni.Lock

public class Lock
extends java.lang.Object

Lock

Author:

Mladen Turk

APR_LOCK_FCNTL

public static final int APR_LOCK_FCNTL

Enumerated potential types for APR process locking methods
Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.

See Also:

Constant Field Values

APR_LOCK_FLOCK

public static final int APR_LOCK_FLOCK

fcntl()

See Also:

Constant Field Values

APR_LOCK_SYSVSEM

public static final int APR_LOCK_SYSVSEM

flock()

See Also:

Constant Field Values

APR_LOCK_PROC_PTHREAD

public static final int APR_LOCK_PROC_PTHREAD

System V Semaphores

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Constant Field Values

APR_LOCK_POSIXSEM

public static final int APR_LOCK_POSIXSEM

POSIX pthread process-based locking

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Constant Field Values

APR_LOCK_DEFAULT

public static final int APR_LOCK_DEFAULT

POSIX semaphore process-based locking

See Also:

Constant Field Values

Lock

public Lock()

create

public static long create(java.lang.String fname,
                          int mech,
                          long pool)
                   throws Error

Create and initialize a mutex that can be used to synchronize processes.
Warning : Check APR_HAS_foo_SERIALIZE defines to see if the platform supports APR_LOCK_foo. Only APR_LOCK_DEFAULT is portable.

Parameters:

fname - A file name to use if the lock mechanism requires one. This argument should always be provided. The lock code itself will determine if it should be used.

mech - The mechanism to use for the interprocess lock, if any; one of

            APR_LOCK_FCNTL
            APR_LOCK_FLOCK
            APR_LOCK_SYSVSEM
            APR_LOCK_POSIXSEM
            APR_LOCK_PROC_PTHREAD
            APR_LOCK_DEFAULT     pick the default mechanism for the platform
 

pool - the pool from which to allocate the mutex.

Returns:

Newly created mutex.

Throws:

Error

childInit

public static long childInit(java.lang.String fname,
                             long pool)
                      throws Error

Re-open a mutex in a child process. This function must be called to maintain portability, even if the underlying lock mechanism does not require it.

Parameters:

fname - A file name to use if the mutex mechanism requires one. This argument should always be provided. The mutex code itself will determine if it should be used. This filename should be the same one that was passed to apr_proc_mutex_create().

pool - The pool to operate on.

Returns:

Newly opened mutex.

Throws:

Error

lock

public static int lock(long mutex)

Acquire the lock for the given mutex. If the mutex is already locked, the current thread will be put to sleep until the lock becomes available.

Parameters:

mutex - the mutex on which to acquire the lock.

trylock

public static int trylock(long mutex)

Attempt to acquire the lock for the given mutex. If the mutex has already been acquired, the call returns immediately with APR_EBUSY. Note: it is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine if the return value was APR_EBUSY, for portability reasons.

Parameters:

mutex - the mutex on which to attempt the lock acquiring.

unlock

public static int unlock(long mutex)

Release the lock for the given mutex.

Parameters:

mutex - the mutex from which to release the lock.

destroy

public static int destroy(long mutex)

Destroy the mutex and free the memory associated with the lock.

Parameters:

mutex - the mutex to destroy.

lockfile

public static java.lang.String lockfile(long mutex)

Return the name of the lockfile for the mutex, or NULL if the mutex doesn't use a lock file

name

public static java.lang.String name(long mutex)

Display the name of the mutex, as it relates to the actual method used. This matches the valid options for Apache's AcceptMutex directive

Parameters:

mutex - the name of the mutex

defname

public static java.lang.String defname()

Display the name of the default mutex: APR_LOCK_DEFAULT