Mutex

Class

Mutex implements a simple semaphore that can be used to coordinate access to shared data from multiple concurrent threads.

Example:

semaphore = Mutex.new

a = Thread.new {
  semaphore.synchronize {
    # access shared resource
  }
}

b = Thread.new {
  semaphore.synchronize {
    # access shared resource
  }
}

Class Methods

Mutex.new → mutex

thread_sync.c View on GitHub

          
            static VALUE
mutex_initialize(VALUE self)
{
    return self;
}

Creates a new Mutex

Instance Methods

mutex.lock → self

thread_sync.c View on GitHub

          
            VALUE
rb_mutex_lock(VALUE self)
{
    return do_mutex_lock(self, 1);
}

Attempts to grab the lock and waits if it isn’t available. Raises ThreadError if mutex was locked by the current thread.

mutex.locked? → true or false

thread_sync.c View on GitHub

          
            VALUE
rb_mutex_locked_p(VALUE self)
{
    rb_mutex_t *mutex = mutex_ptr(self);

    return mutex->fiber ? Qtrue : Qfalse;
}

Returns true if this lock is currently held by some thread.

mutex.owned? → true or false

thread_sync.c View on GitHub

          
            VALUE
rb_mutex_owned_p(VALUE self)
{
    rb_fiber_t *fiber = GET_EC()->fiber_ptr;
    rb_mutex_t *mutex = mutex_ptr(self);

    return mutex_owned_p(fiber, mutex);
}

Returns true if this lock is currently held by current thread.

mutex.sleep(timeout = nil) → number

thread_sync.c View on GitHub

          
            static VALUE
mutex_sleep(int argc, VALUE *argv, VALUE self)
{
    VALUE timeout;

    timeout = rb_check_arity(argc, 0, 1) ? argv[0] : Qnil;
    return rb_mutex_sleep(self, timeout);
}

Releases the lock and sleeps timeout seconds if it is given and non-nil or forever. Raises ThreadError if mutex wasn’t locked by the current thread.

When the thread is next woken up, it will attempt to reacquire the lock.

Note that this method can wakeup without explicit Thread#wakeup call. For example, receiving signal and so on.

mutex.synchronize { ... } → result of the block

thread_sync.c View on GitHub

          
            static VALUE
rb_mutex_synchronize_m(VALUE self)
{
    if (!rb_block_given_p()) {
        rb_raise(rb_eThreadError, "must be called with a block");
    }

    return rb_mutex_synchronize(self, rb_yield, Qundef);
}

Obtains a lock, runs the block, and releases the lock when the block completes. See the example under Mutex.

mutex.try_lock → true or false

thread_sync.c View on GitHub

          
            VALUE
rb_mutex_trylock(VALUE self)
{
    rb_mutex_t *mutex = mutex_ptr(self);

    if (mutex->fiber == 0) {
        rb_fiber_t *fiber = GET_EC()->fiber_ptr;
        rb_thread_t *th = GET_THREAD();
        mutex->fiber = fiber;

        mutex_locked(th, self);
        return Qtrue;
    }

    return Qfalse;
}

Attempts to obtain the lock and returns immediately. Returns true if the lock was granted.

mutex.unlock → self

thread_sync.c View on GitHub

          
            VALUE
rb_mutex_unlock(VALUE self)
{
    const char *err;
    rb_mutex_t *mutex = mutex_ptr(self);
    rb_thread_t *th = GET_THREAD();

    err = rb_mutex_unlock_th(mutex, th, GET_EC()->fiber_ptr);
    if (err) rb_raise(rb_eThreadError, "%s", err);

    return self;
}

Releases the lock. Raises ThreadError if mutex wasn’t locked by the current thread.