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

Example:

semaphore = Thread::Mutex.new

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

b = Thread.new {
  semaphore.synchronize {
    # access shared resource
  }
}
Methods
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Class Public methods

Thread::Mutex.new → mutex

Creates a new Mutex

Source: show 

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

Instance Public methods

mutex.lock → self

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

Source: show 

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

mutex.locked? → true or false

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

Source: show 

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

    return RBOOL(mutex->fiber);
}

mutex.owned? → true or false

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

Source: show 

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);
}

mutex.sleep(timeout = nil) → number or nil

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.

Returns the slept time in seconds if woken up, or nil if timed out.

Source: show 

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);
}

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

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

Source: show 

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);
}

mutex.try_lock → true or false

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

Source: show 

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

    if (mutex->fiber == 0) {
        RUBY_DEBUG_LOG("%p ok", mutex);

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

        mutex_locked(th, self);
        return Qtrue;
    }
    else {
        RUBY_DEBUG_LOG("%p ng", mutex);
        return Qfalse;
    }
}

mutex.unlock → self

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

Source: show 

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;
}