RFR(xs): 6344935: Clarify Object.wait javadoc with respect to spurious wakeups

[Martin Buchholz]

Thanks for working on Object.wait.  Doc writing is never easy, especially
in Object.java.

In the original proposed patch, the word "also" ends up weird, because
spurious wakeup *was* in the list above; we need to do something about that.

On Fri, Aug 11, 2017 at 11:25 AM, Stuart Marks <stuart.marks at oracle.com>
wrote:

> This is an old spec bug. The Object.wait spec lists several different
> reasons a thread could be awakened, but it omits spurious wakeup -- even
> though spurious wakeup is described later on. The fix is simply to add
> spurious wakeup to the list.
>
> There is some discussion in the original bug report:
>
>     https://bugs.openjdk.java.net/browse/JDK-6344935
>
> Patch appended below.
>
> Thanks,
>
> s'marks
>
>
>
> # HG changeset patch
> # User smarks
> # Date 1502475871 25200
> #      Fri Aug 11 11:24:31 2017 -0700
> # Node ID ebd66cd27b298d5bbbdfd348164505ef1195f90e
> # Parent  27b08ab97a607df3a4abff83d8d1a2a1882e5bf1
> 6344935: Clarify Object.wait javadoc with respect to spurious wakeups
> Reviewed-by: XXX
>
> diff -r 27b08ab97a60 -r ebd66cd27b29 src/java.base/share/classes/ja
> va/lang/Object.java
> --- a/src/java.base/share/classes/java/lang/Object.java Thu Aug 03
> 09:04:47 2017 -0700
> +++ b/src/java.base/share/classes/java/lang/Object.java Fri Aug 11
> 11:24:31 2017 -0700
> @@ -318,7 +318,7 @@
>       * place itself in the wait set for this object and then to relinquish
>       * any and all synchronization claims on this object. Thread
> <var>T</var>
>       * becomes disabled for thread scheduling purposes and lies dormant
> -     * until one of four things happens:
> +     * until one of five things happens:
>       * <ul>
>       * <li>Some other thread invokes the {@code notify} method for this
>       * object and thread <var>T</var> happens to be arbitrarily chosen as
> @@ -330,7 +330,9 @@
>       * <li>The specified amount of real time has elapsed, more or less.
> If
>       * {@code timeout} is zero, however, then real time is not taken into
>       * consideration and the thread simply waits until notified.
> +     * <li>Thread <var>T</var> is awakened spuriously. (See below.)
>       * </ul>
> +     * <p>
>       * The thread <var>T</var> is then removed from the wait set for this
>       * object and re-enabled for thread scheduling. It then competes in
> the
>       * usual manner with other threads for the right to synchronize on the
>
>