tree 7863a25ade9b08ed78fd4e76aacded61d427b971
parent b93e8e7aa7f03c32cddfd718807c825beac13107
author Andrey Loskutov <loskutov@gmx.de> 1626425071 +0200
committer Andrey Loskutov <loskutov@gmx.de> 1626559445 -0400

Bug 574897 - Switch JobManager to nanoTime() and monotonic time

Usage of System.currentTimeMillis() in Jobs framework is problematic,
because System.currentTimeMillis() API depends on external time sources
and may go backwards and forwards at any time, contrary to our "human"
understanding of the "monotonic" time that can never go back. However,
code responsible for scheduling and joining on jobs depends on time
values delivered by that API and I assume may be confused if time goes
backwards.

Since Java 5, System.nanoTime() was added to allow better precision and
less system dependent time measurements. While still not strictly
monotonic, it is  less problematic as System.currentTimeMillis(),
because it is not depending on system time changes that could be made by
user or by synchronization of local time with NTP server.

This change switches JobManager and related code to use
System.nanoTime() and introduces JobManager.now() as a source for
monotonic non-negative time values independent on local time and
consistent between multiple threads.

Change-Id: I6e90b4c962318705062148c1929838885404ad26
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.runtime/+/183139
Tested-by: Platform Bot <platform-bot@eclipse.org>