From e28951a8d5019524b0babf8ef8ba8b184bd0773a Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Mon, 4 Jan 2016 22:54:23 -0500
Subject: [PATCH] Move the mutation table into thread data.

---
 gc.c                      |  4 ++++
 include/cyclone/runtime.h |  4 ----
 include/cyclone/types.h   |  6 +++++-
 runtime.c                 | 27 +++++++++++++++------------
 4 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/gc.c b/gc.c
index 480dacc7..cf5acd65 100644
--- a/gc.c
+++ b/gc.c
@@ -1199,6 +1199,7 @@ void gc_thread_data_init(gc_thread_data *thd, int mut_num, char *stack_base, lon
   thd->stack_traces = calloc(MAX_STACK_TRACES, sizeof(char *));
   thd->stack_trace_idx = 0;
   thd->stack_prev_frame = NULL;
+  thd->mutations = NULL;
 //  thd->thread = NULL;
   thd->thread_state = CYC_THREAD_STATE_NEW;
   //thd->mutator_num = mut_num;
@@ -1234,6 +1235,9 @@ void gc_thread_data_free(gc_thread_data *thd)
     if (thd->moveBuf) free(thd->moveBuf);
     if (thd->mark_buffer) free(thd->mark_buffer);
     if (thd->stack_traces) free(thd->stack_traces);
+    if (thd->mutations) {
+      clear_mutations(thd);
+    }
     free(thd);
   }
 }
diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 4f35bcd7..4d0dbf69 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -211,10 +211,6 @@ object find_or_add_symbol(const char *name);
 extern list global_table;
 void add_global(object *glo);
 
-void add_mutation(object var, object value);
-void clear_mutations();
-extern list mutation_table;
-
 void dispatch(void *data, int argc, function_type func, object clo, object cont, object args);
 void dispatch_va(void *data, int argc, function_type_va func, object clo, object cont, object args);
 void do_dispatch(void *data, int argc, function_type func, object clo, object *buffer);
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 40b9721c..8c482ebe 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -66,7 +66,8 @@ struct gc_thread_data_t {
   // Data needed to initiate stack-based minor GC
   char *stack_start;
   char *stack_limit;
-//TODO: store stack traces per thread
+  // Minor GC write barrier
+  void *mutations;
   // List of objects moved to heap during minor GC
   void **moveBuf;
   int moveBufLen;
@@ -452,4 +453,7 @@ void gc_mutator_thread_runnable(gc_thread_data *thd, object result);
 gc_heap *gc_get_heap();
 int gc_minor(void *data, object low_limit, object high_limit, closure cont, object *args, int num_args);
 
+void add_mutation(void *data, object var, object value);
+void clear_mutations(void *data);
+
 #endif /* CYCLONE_TYPES_H */
diff --git a/runtime.c b/runtime.c
index f14301cf..266de942 100644
--- a/runtime.c
+++ b/runtime.c
@@ -312,30 +312,33 @@ void debug_dump_globals()
 
 /* END Global table */
 
-/* Mutation table
+/* Mutation table functions
  *
  * Keep track of mutations (EG: set-car!) so that new
  * values are transported to the heap during GC.
+ * Note these functions and underlying data structure are only used by
+ * the calling thread, so locking is not required.
  */
-list mutation_table = nil;
 
-void add_mutation(object var, object value){
+void add_mutation(void *data, object var, object value){
+  gc_thread_data *thd = (gc_thread_data *)data;
   if (is_object_type(value)) {
-    mutation_table = mcons(var, mutation_table);
+    thd->mutations = mcons(var, thd->mutations);
   }
 }
 
 /* TODO: consider a more efficient implementation, such as reusing old nodes
          instead of reclaiming them each time
  */
-void clear_mutations() {
-  list l = mutation_table, next;
+void clear_mutations(void *data) {
+  gc_thread_data *thd = (gc_thread_data *)data;
+  list l = thd->mutations, next;
   while (!nullp(l)) {
     next = cdr(l);
     free(l);
     l = next;
   }
-  mutation_table = nil;
+  thd->mutations = nil;
 }
 /* END mutation table */
 
@@ -897,7 +900,7 @@ object Cyc_set_car(void *data, object l, object val) {
     if (Cyc_is_cons(l) == boolean_f) Cyc_invalid_type_error(data, cons_tag, l);
     gc_mut_update((gc_thread_data *)data, car(l), val);
     car(l) = val;
-    add_mutation(l, val);
+    add_mutation(data, l, val);
     return l;
 }
 
@@ -905,7 +908,7 @@ object Cyc_set_cdr(void *data, object l, object val) {
     if (Cyc_is_cons(l) == boolean_f) Cyc_invalid_type_error(data, cons_tag, l);
     gc_mut_update((gc_thread_data *)data, cdr(l), val);
     cdr(l) = val;
-    add_mutation(l, val);
+    add_mutation(data, l, val);
     return l;
 }
 
@@ -926,7 +929,7 @@ object Cyc_vector_set(void *data, object v, object k, object obj) {
   ((vector)v)->elts[idx] = obj;
   // TODO: probably could be more efficient here and also pass
   //       index, so only that one entry needs GC.
-  add_mutation(v, obj);
+  add_mutation(data, v, obj);
   return v;
 }
 
@@ -2366,7 +2369,7 @@ int gc_minor(void *data, object low_limit, object high_limit, closure cont, obje
   // Transport mutations
   {
     list l;
-    for (l = mutation_table; !nullp(l); l = cdr(l)) {
+    for (l = ((gc_thread_data *)data)->mutations; !nullp(l); l = cdr(l)) {
       object o = car(l);
       if (type_of(o) == cons_tag) {
           gc_move2heap(car(o));
@@ -2385,7 +2388,7 @@ int gc_minor(void *data, object low_limit, object high_limit, closure cont, obje
       }
     }
   }
-  clear_mutations(); // Reset for next time
+  clear_mutations(data); // Reset for next time
 
   // Transport globals
   gc_move2heap(Cyc_global_variables); // Internal global used by the runtime