As explained in 'The "Double-Checked Locking is Broken"
Declaration'[*], Java's memory model does not support double-checked
locking:
class LazyReadableChannel {
private ReachableChannel rc = null;
public ReadableChannel get() {
if (rc == null) {
synchronized (this) {
if (rc == null) {
rc = new ReadableChannel();
}
}
}
return rc;
}
}
With JDK 5 and newer, there is a formal memory model that ensures this
works if "rc" is volatile, but it is still not thread-safe without
that.
Fortunately, this ReadableChannelSupplier is never passed between
threads, so it does not need to be thread-safe. Simplify by removing
the synchronization.
[*] https://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
Change-Id: I0698ee6618d734fc129dd4f63fc047c1c17c94a9
Signed-off-by: Jonathan Nieder <jrn@google.com>