--- a/js/src/jsgc.cpp	2012-12-15 17:19:27.919779697 +0100
+++ b/js/src/jsgc.cpp	2012-12-15 17:22:09.267787141 +0100
@@ -92,16 +92,18 @@
 #include "vm/Debugger.h"
 #include "vm/String.h"
 
 #include "jsobjinlines.h"
 
 #include "vm/CallObject-inl.h"
 #include "vm/String-inl.h"
 
+#include "yarr/PageBlock.h" /* for pageSize() */
+
 #ifdef MOZ_VALGRIND
 # define JS_VALGRIND
 #endif
 #ifdef JS_VALGRIND
 # include <valgrind/memcheck.h>
 #endif
 
 using namespace mozilla;
@@ -2380,16 +2382,23 @@ ReleaseObservedTypes(JSContext *cx)
     }
 
     return releaseTypes;
 }
 
 static void
 DecommitFreePages(JSContext *cx)
 {
+    /*
+     * If the ArenaSize is smaller than a memory page, we don't attempt to
+     * decommit anything because DecommitMemory() would always fail.
+     */
+    if (ArenaSize < pageSize())
+        return;
+
     JSRuntime *rt = cx->runtime;
 
     for (GCChunkSet::Range r(rt->gcChunkSet.all()); !r.empty(); r.popFront()) {
         Chunk *chunk = r.front();
         while (chunk) {
             ArenaHeader *aheader = static_cast<ArenaHeader*>(chunk->info.freeArenasHead);
 
             /*
@@ -2402,24 +2411,23 @@ DecommitFreePages(JSContext *cx)
             while (aheader) {
                 /* Store aside everything we will need after decommit. */
                 ArenaHeader *next = aheader->next;
 
                 bool success = DecommitMemory(aheader, ArenaSize);
                 if (!success) {
                     aheader->next = chunk->info.freeArenasHead;
                     chunk->info.freeArenasHead = aheader;
-                    continue;
+                } else {
+                    size_t arenaOffset = Chunk::arenaIndex(reinterpret_cast<uintptr_t>(aheader));
+                    chunk->decommittedArenas.set(arenaOffset);
+                    --chunk->info.numArenasFreeCommitted;
+                    --rt->gcNumFreeArenas;
                 }
 
-                size_t arenaOffset = Chunk::arenaIndex(reinterpret_cast<uintptr_t>(aheader));
-                chunk->decommittedArenas.set(arenaOffset);
-                --chunk->info.numArenasFreeCommitted;
-                --rt->gcNumFreeArenas;
-
                 aheader = next;
             }
 
             chunk = chunk->info.next;
         }
     }
 }
 

Signed-off-by: Stephan Schreiber <info@fs-driver.org>