From 0cf27b90080cab66a1a2e0025893bafc601d3ed7 Mon Sep 17 00:00:00 2001
From: Terrence Cole <terrence@mozilla.com>
Date: Mon, 23 Feb 2015 11:15:43 -0800
Subject: [PATCH] Bug 1135141 - Make LAST_DITCH GC more robust; r=jonco

---
 js/src/gc/GCRuntime.h |  2 +-
 js/src/jsgc.cpp       | 11 +++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/js/src/gc/GCRuntime.h b/js/src/gc/GCRuntime.h
index 24ba7507f01..e43ae38805c 100644
--- a/js/src/gc/GCRuntime.h
+++ b/js/src/gc/GCRuntime.h
@@ -921,7 +921,7 @@ class GCRuntime
     void protectRelocatedArenas(ArenaHeader *relocatedList);
     void unprotectRelocatedArenas(ArenaHeader *relocatedList);
 #endif
-    void finishCollection();
+    void finishCollection(JS::gcreason::Reason reason);
 
     void computeNonIncrementalMarkingForValidation();
     void validateIncrementalMarking();
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index baab0d7e3bf..f4faaa2abc1 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -5546,7 +5546,7 @@ GCRuntime::compactPhase(bool lastGC, JS::gcreason::Reason reason)
 }
 
 void
-GCRuntime::finishCollection()
+GCRuntime::finishCollection(JS::gcreason::Reason reason)
 {
     MOZ_ASSERT(marker.isDrained());
     marker.stop();
@@ -5566,6 +5566,13 @@ GCRuntime::finishCollection()
     }
 
     lastGCTime = currentTime;
+
+    // If this is an OOM GC reason, wait on the background sweeping thread
+    // before returning to ensure that we free as much as possible.
+    if (reason == JS::gcreason::LAST_DITCH || reason == JS::gcreason::MEM_PRESSURE) {
+        gcstats::AutoPhase ap(stats, gcstats::PHASE_WAIT_BACKGROUND_THREAD);
+        rt->gc.waitBackgroundSweepOrAllocEnd();
+    }
 }
 
 /* Start a new heap session. */
@@ -5933,7 +5940,7 @@ GCRuntime::incrementalCollectSlice(SliceBudget &budget, JS::gcreason::Reason rea
         if (isCompacting && compactPhase(lastGC, reason) == NotFinished)
             break;
 
-        finishCollection();
+        finishCollection(reason);
 
         incrementalState = NO_INCREMENTAL;
         break;