diff -r 4ccd6253e3e9 libgo/runtime/go-go.c
--- a/libgo/runtime/go-go.c	Mon Jul 26 04:21:01 2010 -0700
+++ b/libgo/runtime/go-go.c	Mon Jul 26 05:47:38 2010 -0700
@@ -114,6 +114,11 @@
 
   free (list_entry);
   m->list_entry = NULL;
+
+  MCache_ReleaseAll (m->mcache);
+  __builtin_memset (m->mcache, 0, sizeof (struct MCache));
+  FixAlloc_Free (&mheap.cachealloc, m->mcache);
+  m->mcache = NULL;
 }
 
 /* Start the thread.  */
@@ -511,7 +516,7 @@
   struct __go_thread_id *p;
 
   for (p = __go_all_thread_ids; p != NULL; p = p->next)
-    MCache_ReleaseAll(p->m->mcache);
+    MCache_ReleaseAll (p->m->mcache);
 }
 
 /* Start the other threads after garbage collection.  */
diff -r 4ccd6253e3e9 libgo/runtime/malloc.goc
--- a/libgo/runtime/malloc.goc	Mon Jul 26 04:21:01 2010 -0700
+++ b/libgo/runtime/malloc.goc	Mon Jul 26 05:47:38 2010 -0700
@@ -248,6 +248,10 @@
 	MCache *c;
 
 	c = FixAlloc_Alloc(&mheap.cachealloc);
+
+	// Clear the free list used by FixAlloc; assume the rest is zeroed.
+	c->list[0].list = nil;
+
 	mstats.mcache_inuse = mheap.cachealloc.inuse;
 	mstats.mcache_sys = mheap.cachealloc.sys;
 	return c;