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lib/Acme/Parataxis/Sync/Mutex.pod  view on Meta::CPAN

Returns the number of fibers currently parked waiting to acquire the lock. Note that when C<unlock()> is called,
ownership is transferred and the waiter is dequeued immediately, so C<waiters> decrements before the waking fiber
actually resumes execution.

=head1 Recipes

=head2 Scoped critical sections

Always prefer guards over manual C<lock()>/C<unlock()> pairs to ensure releases occur even during exceptions:

    sub update_shared_state ($mutex, $data) {
        my $guard = $mutex->guard;
        validate($data);    # if this dies, $guard->DESTROY safely unlocks!
        apply($data);
    }

=head2 Non-blocking skip

Use C<try_lock()> to perform work only when no contention exists:

    fiber {

lib/Acme/Parataxis/Sync/RwLock.pod  view on Meta::CPAN

    async {
        my $outer_guard = $rwlock->read_guard;
        my $val1 = fetch_field('name');
        my $val2 = fetch_field('role');
    };

=head2 Deadlock prevention during writes

Because upgrading a read hold to a write hold is forbidden, release read holds before requesting a write lock:

    sub update_record ($id, $new_val) {
        # Check current value under read lock:
        my $needs_update = 0;
        {
            my $guard = $rwlock->read_guard;
            $needs_update = 1 if $data{$id} ne $new_val;
        }

        # Drop read hold before requesting write lock:
        if ($needs_update) {
            my $guard = $rwlock->write_guard;