Jeff,
On 1/06/2012 10:19 AM, Jeff Hain wrote:
Hi.
185 public boolean waitFor(long timeout, TimeUnit unit)
186 throws InterruptedException {
187 long now = System.nanoTime();
188
189 long end = now +
190 (timeout<= 0 ? 0 : TimeUnit.NANOSECONDS.convert(timeout, unit));
191
192 if (end<= 0) // overflow
193 end = Long.MAX_VALUE;
194
195 long rem = end - now;
196 do {
197 try {
198 exitValue();
199 return true;
200 } catch(IllegalThreadStateException ex) {
201 if(rem> 0)
202 Thread.sleep(
203 Math.min(TimeUnit.NANOSECONDS.toMillis(rem) + 1,
100));
204 }
205 rem = end - System.nanoTime();
206 } while(rem> 0);
207 return false;
208 }
If System.nanoTime() is close to wrapping, this code would consider overflow
even for a not-so-large timeout,
If System.nanoTime is close to wrapping then we have all sorts of
problems to worry about. But you are right. The way to handle this with
no overflow issues is to track the elapsed time (System.nanoTime() -
start) which will always give a positive result when less than 2^63
nanoseconds elapse. That then gets subtracted from the requested timeout
to give the rem value.
and the wait could stop earlier than expected.
(Also "now" should rather be called "startTime" or so (since at some point it's
no longer current time).)
One could do as in ScheduledThreadPoolExecutor, and use an offset on
System.nanoTime().
Aside: I don't see that in latest version of STPE.
Cheers,
David
-----
Or, just remove lines 192-194 : it's not really a problem if "end" wraps, since
it should unwrap
when doing "end - System.nanoTime()" (supposing we don't spend centuries in the
method).
Or, only work with delta (also supposing we don't wait for centuries), never
explicitly considering
an "end" value, like this:
public boolean waitFor(long timeout, TimeUnit unit)
throws InterruptedException {
final long startNS = System.nanoTime();
final long timeoutNS = (timeout<= 0 ? 0 : unit.toNanos(timeout));
long remNS = timeoutNS;
do {
try {
exitValue();
return true;
} catch(IllegalThreadStateException ex) {
if(remNS> 0)
Thread.sleep(
Math.min(TimeUnit.NANOSECONDS.toMillis(remNS) + 1, 100));
}
remNS = timeoutNS - (System.nanoTime() - startNS);
} while(remNS> 0);
return false;
}
-Jeff
