From 161986fc56bc951eb193c4c669b3e7b5c2a317ae Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 4 Jul 2013 09:41:30 -0600
Subject: [PATCH] fix GC bug

GC during allocation of a pair, weak box, ephemeron, or
weak array went wrong if the GC-notification callback
allocated any of those kinds of things.

(Bug found by running tests in GC-stress mode.)
(cherry picked from commit 49fbca5b1830bc4bddb8522d7647518227a32dd0)
---
 src/racket/gc2/newgc.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/racket/gc2/newgc.c b/src/racket/gc2/newgc.c
index d48d9649a6..6f12a37ff6 100644
--- a/src/racket/gc2/newgc.c
+++ b/src/racket/gc2/newgc.c
@@ -4788,10 +4788,25 @@ static void garbage_collect(NewGC *gc, int force_full, int switching_master, Log
 #ifdef MZ_USE_PLACES
     is_master = (gc == MASTERGC);
 #endif
+    gc->dumping_avoid_collection++;
+
+    /* Inform might allocate, which might need park: */
+    gc->park_save[0] = gc->park[0];
+    gc->park_save[1] = gc->park[1];
+    gc->park[0] = NULL;
+    gc->park[1] = NULL;
+
     gc->GC_collect_inform_callback(is_master, gc->gc_full, 
                                    old_mem_use + old_gen0, gc->memory_in_use, 
                                    old_mem_allocated, mmu_memory_allocated(gc->mmu),
                                    gc->child_gc_total);
+
+    gc->park[0] = gc->park_save[0];
+    gc->park[1] = gc->park_save[1];
+    gc->park_save[0] = NULL;
+    gc->park_save[1] = NULL;
+
+    --gc->dumping_avoid_collection;
   }
 #ifdef MZ_USE_PLACES
   if (lmi) {