ReadWriteLock

... A lock with shared/exclusive access modes, for the Raku language.

Features

• Does what a basic Lock does, just slower and with more bugs ;)
• Reentrant: the lock can be taken again by a thread that is already holding it It needs to be unlocked the same number of times it was locked before it can be taken by another thread
• Fair in the sense of first-come-first-serve
• Shared access: multiple 'readers' can share the lock, yet access is mutually exclusive between 'readers' and 'writers'
• Lock Upgrade: you can upgrade a shared access mode to an exclusive without unlocking first, if no other thread is interferring. In this case you do not need to unlock twice.

Planned Features

• Read-for-write access mode that guarantees that a lock upgrade can be taken
• Async version that returns threads to the threadpool and returns a promise from lock()

Example Usage

use ReadWriteLock;

my $l = ReadWriteLock.new;

my $thread-a = Thread.start({
    $l.lock-shared();
    for ^5 {
        sleep 1;
        say "thread A doing something under protection of the lock";
    }
    $l.unlock();
});

my $thread-b = Thread.start({
    $l.protect-shared({
        for ^5 {
            sleep 1;
            say "thread B doing something under protection of the lock";
        }
    });
});

my $thread-c = Thread.start({
    $l.protect-exclusive({
        for ^5 {
            sleep 1;
            say "thread C doing something under exclusive protection of the lock";
        }
    });
});

$thread-a.join;
$thread-b.join;
$thread-c.join;

Documentation

Please see the POD in lib/ReadWriteLock.rakumod for more documentation and usage scenarios.

License

ReadWriteLock is licensed under the Artistic License 2.0.

Feedback and Contact

Please let me know what you think: Robert Lemmen robertle@semistable.com