Change suspend order in GC

The GC currently does this:

 1. acquire heapLock
 2. suspend all threads
 3. acquire heapWorkerLock

When the HeapWorker thread is suspended in #2, it might be holding
the lock we want in step #3, leading to VM deadlock.  This change
reverses the order of #2 and #3, which should allow the HeapWorker
thread to progress to a point where it releases the lock before
the GC requests the suspension.

If futexes are being unfair, the GC might have to wait a bit
longer while the HeapWorker does stuff (it might unlock, do work,
and re-lock without the scheduler giving time to the GC thread;
with the old scheme the HeapWorker would see the pending thread
suspension immediately and stop).  A better fix is planned.

Bug 3340837

Change-Id: Ib9b37c130903a2800f8f28ae61540a428dbfc5be

0 files changed, 0 insertions, 0 deletions