Summary: Make sure that two marking cycles do not overlap, i.e., a new one can only start after the concurrent marking thread finishes all its work. In the fix I piggy-back a couple of minor extra fixes: some general code reformatting for consistency (only around the code I modified), the removal of a field (G1CollectorPolicy::_should_initiate_conc_mark) which doesn't seem to be used at all (it's only set but never read), as well as moving the "is GC locker active" test earlier into the G1 pause / Full GC and using a more appropriate method for it.
Reviewed-by: johnc, jmasa, jcoomes, ysr

Summary: Calling the methods region_stack_push() and region_stack_pop() concurrent is not MT-safe. The assumption is that we will only call region_stack_push() during a GC pause and region_stack_pop() during marking. Unfortunately, we also call region_stack_push() during marking which seems to be introducing subtle marking failures. This change introduces lock-based methods for pushing / popping to be called during marking.
Reviewed-by: iveresov, johnc

Summary: Newly-created threads always had the active field of their SATB queue initialized to false, even if they were created during marking. As a result, updates from threads created during a marking cycle were never enqueued and never processed. The fix includes remaining a method from active() to is_active() for readability and naming consistency.
Reviewed-by: ysr, johnc

Summary: If CM task was aborted while scanning the last object of the specified region and the size of that object is equal to bitmap's granularity then the next offset would be equal or over the region limit which is exactly what the assertion states.
Reviewed-by: ysr, tonyp, jmasa

Summary: Rename marking stack sizing flags to be common between G1 and CMS
Reviewed-by: ysr, tonyp

Summary: Rename G1 parameters to make them more consistent.
Reviewed-by: jmasa, johnc

Summary: Reworked the concurrent refinement: threads activation, feedback-based threshold adjustment, other miscellaneous fixes.
Reviewed-by: apetrusenko, tonyp

Reviewed-by: tonyp, ysr

Summary: change more guarantees in concurrent marking into asserts.
Reviewed-by: apetrusenko, iveresov

Summary: Remove incorrect guarantee.
Reviewed-by: apetrusenko, iveresov

Summary: When G1 is enabled, thread dumps are inconsistent as the info for some of the G1 threads is not formatted properly.
Reviewed-by: ysr, johnc

Summary: Revamp the reachable object dump debugging facility.
Reviewed-by: jmasa, apetrusenko

Summary: Make a special root-list for those few nmethods which might contain non-perm oops.
Reviewed-by: twisti, kvn, never, jmasa, ysr

Reviewed-by: jcoomes, tonyp

Summary: Removing the concurrent overhead tracker from G1, along with the GC overhead reporter and the G1AccountConcurrentOverhead (both of which rely on the the concurrent overhead tracker).
Reviewed-by: iveresov, johnc

Summary: Update copyright for files that have been modified in 2009, up to 07/09
Reviewed-by: tbell, ohair

Summary: Modifications to G1 so as to allow the use of compressed oops.
Reviewed-by: apetrusenko, coleenp, jmasa, kvn, never, phh, tonyp

Summary: Missed updating two variable names when improving the code for 6850869.
Reviewed-by: iveresov, jmasa, ysr

Summary: RSet scrubbing incorrectly deletes RSet entries that point to regions tagged as "continues humongous" due to a race when RSet scrubbing iterates over regions in parallel.
Reviewed-by: apetrusenko, iveresov

Summary: extend G1 marking verification to use either the "prev" or "next" marking information, as appropriate.
Reviewed-by: johnc, ysr

Summary: Change G1 flag names to be more consistent and disable some in 'product' mode.
Reviewed-by: tonyp, iveresov

Summary: We should mark the regions that continue humongous regions as live if the first region is live.
Reviewed-by: tonyp

Summary: Allow Hotspot builds with latest Windows SDK 6.1 on 64bit Windows 2003
Reviewed-by: ohair, tbell, jcoomes

Summary: A few small fixes to remove some inconsistencies in the concurrent mark-related verbose GC output.
Reviewed-by: jmasa

Summary: Update copyright for files that have been modified starting July 2008 to Dec 2008
Reviewed-by: katleman, ohair, tbell

Summary: Renamed Reference{Policy,Pocessor} methods from snap{,_policy}() to setup{,_policy}()
Reviewed-by: apetrusenko

Summary: For current soft-ref clearing policies, we can decide at marking time if a soft-reference will definitely not be cleared, postponing the decision of whether it will definitely be cleared to the final reference processing phase. This can be especially beneficial in the case of concurrent collectors where the marking is usually concurrent but reference processing is usually not.
Reviewed-by: jmasa

Summary: Under certain circumstances, two cleanup threads can claim and process the same region.
Reviewed-by: apetrusenko, ysr

6710665: G1: guarantee(_cm->out_of_regions() && _cm->region_stack_empty() && _task_queue->size() == 0, ...)
Summary: Remove the incorrect assumptions from guarantee()s.
Reviewed-by: ysr, tonyp

Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr