You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: entry.rs
    path of file: ./repos/phaser/phaser/vendor/tokio/src/time/driver
    
    the code of the file until where you have to start completion: //! Timer state structures.
//!
//! This module contains the heart of the intrusive timer implementation, and as
//! such the structures inside are full of tricky concurrency and unsafe code.
//!
//! 
    
    pub(crate) fn cancel(self: Pin<&mut Self>) {
        // We need to perform an acq/rel fence with the driver thread, and the
        // simplest way to do so is to grab the driver lock.
        //
        // Why is this necessary? We're about to release this timer's memory for
        // some other non-timer use. However, we've been doing a bunch of
        // relaxed (or even non-atomic) writes from the driver thread, and we'll
        // be doing more from _this thread_ (as this memory is interpreted as
        // something else).
        //
        // It is critical to ensure that, from the point of view of the driver,
        // those future non-timer writes happen-after the timer is fully fired,
        // and from the purpose of this thread, the driver's writes all
        // happen-before we drop the timer. This in turn requires us to perform
        // an acquire-release barrier in _both_ directions between the driver
        // and dropping thread.
        //
        // The lock acquisition in clear_entry serves this purpose. All of the
        // driver manipulations happen with the lock held, so we can just take
        // the lock and be sure that this drop happens-after everything the
        // driver did so far and happens-before everything the driver does in
        // the future. While we have the lock held, we also go ahead and
        // deregister the entry if necessary.
        unsafe { self.driver.clear_entry(NonNull::from(self.inner())) };
    }