System.nanoTime() can be negative --------------------------------- Key: JGRP-1877 URL: https://issues.jboss.org/browse/JGRP-1877 Project: JGroups Issue Type: Bug Reporter: Bela Ban Assignee: Bela Ban Priority: Critical Fix For: 3.5.1, 3.6 According to the javadoc, {{System.nanoTime()}} should only be used to measure _elapsed time_, but not compute a _target time in the future_, as {{nanoTime()}} might return a a time in the future. Code like the one below might fail: {code:title=Responses.waitFor()|borderStyle=solid} public boolean waitFor(long timeout) { long wait_time; final long target_time=System.nanoTime() + TimeUnit.NANOSECONDS.convert(timeout, TimeUnit.MILLISECONDS); // ns lock.lock(); try { while(!done && (wait_time=target_time - System.nanoTime()) > 0) { try { cond.await(wait_time,TimeUnit.NANOSECONDS); } catch(InterruptedException e) { } } return done; } finally { lock.unlock(); } } {code} When computing {{target_time}}, {{System.nanoTime()}} could return a negative value (numeric overflow) or a value in the future. In the first case, {{target_time}} could be negative, so the method would not block at all. In the latter case, {{target_time}} could be huge, so the method would block for a long time. Investigate all occurrences where we use {{nanoTime()}} to compute a time in the future, and see what impact a future value value could have. Possibly replace with {{System.currentTimeMillis()}} or the _time service_.