diff --git a/src/mzscheme/include/schthread.h b/src/mzscheme/include/schthread.h
index 4ee4665c40..0e3c9763da 100644
--- a/src/mzscheme/include/schthread.h
+++ b/src/mzscheme/include/schthread.h
@@ -258,6 +258,7 @@ typedef struct Thread_Local_Variables {
   long scheme_code_page_total_;
   int locale_on_;
   const mzchar *current_locale_name_;
+  int gensym_counter_;
 /*KPLAKE1*/
 } Thread_Local_Variables;
 
@@ -501,6 +502,7 @@ XFORM_GC_VARIABLE_STACK_THROUGH_THREAD_LOCAL;
 #define scheme_code_page_total XOA (scheme_get_thread_local_variables()->scheme_code_page_total_)
 #define locale_on XOA (scheme_get_thread_local_variables()->locale_on_)
 #define current_locale_name XOA (scheme_get_thread_local_variables()->current_locale_name_)
+#define gensym_counter XOA (scheme_get_thread_local_variables()->gensym_counter_)
 /*KPLAKE2*/
 
 /* **************************************** */
diff --git a/src/mzscheme/src/env.c b/src/mzscheme/src/env.c
index 990fa77885..1f3bdced94 100644
--- a/src/mzscheme/src/env.c
+++ b/src/mzscheme/src/env.c
@@ -354,6 +354,7 @@ Scheme_Env *scheme_engine_instance_init() {
 #ifndef DONT_USE_FOREIGN
   scheme_init_foreign_globals();
 #endif
+  scheme_init_salloc();
 #ifdef MZ_USE_JIT
   scheme_init_jit();
 #endif
diff --git a/src/mzscheme/src/error.c b/src/mzscheme/src/error.c
index 7e3aa33d05..108f285679 100644
--- a/src/mzscheme/src/error.c
+++ b/src/mzscheme/src/error.c
@@ -771,14 +771,18 @@ static long get_print_width(void)
 
 static char *init_buf(long *len, long *_size)
 {
-  long size, print_width;
+  unsigned long local_max_symbol_length;
+  long print_width;
+  long size;
+  
+  local_max_symbol_length = scheme_get_max_symbol_length();
+  print_width             = get_print_width();
 
-  print_width = get_print_width();
+  size = (3 * local_max_symbol_length + 500 + 2 * print_width);
 
+  /* out parameters */
   if (len)
     *len = print_width;
-
-  size = (3 * scheme_max_found_symbol_name + 500 + 2 * print_width);
   if (_size)
     *_size = size;
 
diff --git a/src/mzscheme/src/mzrt.h b/src/mzscheme/src/mzrt.h
index 87d16da239..a18ab2d349 100644
--- a/src/mzscheme/src/mzrt.h
+++ b/src/mzscheme/src/mzrt.h
@@ -110,6 +110,87 @@ void pt_mbox_recv(pt_mbox *mbox, int *type, void **payload, pt_mbox **origin);
 void pt_mbox_send_recv(pt_mbox *mbox, int type, void *payload, pt_mbox *origin, int *return_type, void **return_payload);
 void pt_mbox_destroy(pt_mbox *mbox);
 
+static inline int mzrt_cas(volatile size_t *addr, size_t old, size_t new_val) {
+#if defined(__GNUC__) && !defined(__INTEL_COMPILER)
+# if defined(__i386__)
+  char result;
+  __asm__ __volatile__("lock; cmpxchgl %3, %0; setz %1"
+      : "=m"(*addr), "=q"(result)
+      : "m"(*addr), "r" (new_val), "a"(old) 
+      : "memory");
+  return (int) result;
+# elif defined(__x86_64__)
+  char result;
+  __asm__ __volatile__("lock; cmpxchgq %3, %0; setz %1"
+      : "=m"(*addr), "=q"(result)
+      : "m"(*addr), "r" (new_val), "a"(old) 
+      : "memory");
+  return (int) result;
+# elif defined(__powerpc__) || defined(__ppc__) || defined(__PPC__) \
+     || defined(__powerpc64__) || defined(__ppc64__)
+
+#  if defined(__powerpc64__) || defined(__ppc64__) || defined(__64BIT__)
+/* FIXME: Completely untested.  */
+  AO_t oldval;
+  int result = 0;
+
+  __asm__ __volatile__(
+               "1:ldarx %0,0,%2\n"   /* load and reserve              */
+               "cmpd %0, %4\n"      /* if load is not equal to  */
+               "bne 2f\n"            /*   old, fail     */
+               "stdcx. %3,0,%2\n"    /* else store conditional         */
+               "bne- 1b\n"           /* retry if lost reservation      */
+         "li %1,1\n"       /* result = 1;     */
+               "2:\n"
+              : "=&r"(oldval), "=&r"(result)
+              : "r"(addr), "r"(new_val), "r"(old), "1"(result)
+              : "memory", "cc");
+
+  return result;
+#  else
+  AO_t oldval;
+  int result = 0;
+
+  __asm__ __volatile__(
+               "1:lwarx %0,0,%2\n"   /* load and reserve              */
+               "cmpw %0, %4\n"      /* if load is not equal to  */
+               "bne 2f\n"            /*   old, fail     */
+               "stwcx. %3,0,%2\n"    /* else store conditional         */
+               "bne- 1b\n"           /* retry if lost reservation      */
+         "li %1,1\n"       /* result = 1;     */
+               "2:\n"
+              : "=&r"(oldval), "=&r"(result)
+              : "r"(addr), "r"(new_val), "r"(old), "1"(result)
+              : "memory", "cc");
+
+  return result;
+#  endif
+# else
+# error mzrt_cas not defined on this platform
+# endif
+#elif defined(_MSC_VER)
+# if defined(_AMD64_)
+  return _InterlockedCompareExchange64((LONGLONG volatile *)addr, (LONGLONG)new_val, (LONGLONG)old) == (LONGLONG)old
+# elif _M_IX86 >= 400
+  return _InterlockedCompareExchange((LONG volatile *)addr, (LONG)new_val, (LONG)old) == (LONG)old;
+# endif
+#else
+# error mzrt_cas not defined on this platform
+#endif
+}
+
+static inline void mzrt_ensure_max_cas(unsigned long *atomic_val, unsigned long len) {
+  int set = 0;
+  while(!set) {
+    unsigned long old_val = *atomic_val;
+    if (len > old_val) {
+      set = !mzrt_cas(atomic_val, old_val, len);
+    }
+    else {
+      set = 1;
+    }
+  }
+}
 #endif
 
 #endif
diff --git a/src/mzscheme/src/port.c b/src/mzscheme/src/port.c
index 7ec441323d..17395f6f29 100644
--- a/src/mzscheme/src/port.c
+++ b/src/mzscheme/src/port.c
@@ -310,7 +310,7 @@ HOOK_SHARED_OK Scheme_Object *(*scheme_make_stdin)(void) = NULL;
 HOOK_SHARED_OK Scheme_Object *(*scheme_make_stdout)(void) = NULL;
 HOOK_SHARED_OK Scheme_Object *(*scheme_make_stderr)(void) = NULL;
 
-MZ_DLLSPEC int scheme_binary_mode_stdio;
+SHARED_OK MZ_DLLSPEC int scheme_binary_mode_stdio = 0;
 void scheme_set_binary_mode_stdio(int v) { scheme_binary_mode_stdio =  v; }
 
 THREAD_LOCAL_DECL(static int special_is_ok);
diff --git a/src/mzscheme/src/print.c b/src/mzscheme/src/print.c
index b21bb59cd0..2579f998e2 100644
--- a/src/mzscheme/src/print.c
+++ b/src/mzscheme/src/print.c
@@ -47,7 +47,7 @@ THREAD_LOCAL_DECL(static Scheme_Hash_Table *cache_ht);
 /* read-only globals */
 SHARED_OK static char compacts[_CPT_COUNT_];
 SHARED_OK static Scheme_Hash_Table *global_constants_ht;
-static Scheme_Object *quote_link_symbol = NULL;
+SHARED_OK static Scheme_Object *quote_link_symbol = NULL;
 
 /* Flag for debugging compiled code in printed form: */
 #define NO_COMPACT 0
diff --git a/src/mzscheme/src/salloc.c b/src/mzscheme/src/salloc.c
index 70ed8050fd..12c8247c73 100644
--- a/src/mzscheme/src/salloc.c
+++ b/src/mzscheme/src/salloc.c
@@ -89,6 +89,25 @@ SHARED_OK static int use_registered_statics;
 extern MZ_DLLIMPORT void GC_init();
 #endif
 
+struct free_list_entry {
+  long size; /* size of elements in this bucket */
+  void *elems; /* doubly linked list for free blocks */
+  int count; /* number of items in `elems' */
+};
+
+SHARED_OK static struct free_list_entry *free_list;
+SHARED_OK static int free_list_bucket_count;
+#ifdef MZ_USE_PLACES
+SHARED_OK static mzrt_mutex *free_list_mutex;
+#endif
+
+
+void scheme_init_salloc() {
+#ifdef MZ_USE_PLACES
+  mzrt_mutex_create(&free_list_mutex);
+#endif
+}
+
 void scheme_set_stack_base(void *base, int no_auto_statics)
 {
 #ifdef MZ_PRECISE_GC
@@ -739,15 +758,6 @@ static int fd, fd_created;
 #if defined(MZ_JIT_USE_MPROTECT) || defined(MZ_JIT_USE_WINDOWS_VIRTUAL_ALLOC)
 
 
-FIXME_LATER struct free_list_entry {
-  long size; /* size of elements in this bucket */
-  void *elems; /* doubly linked list for free blocks */
-  int count; /* number of items in `elems' */
-};
-
-static struct free_list_entry *free_list;
-static int free_list_bucket_count;
-
 static long get_page_size()
 {
 # ifdef PAGESIZE
@@ -865,9 +875,14 @@ static long free_list_find_bucket(long size)
 void *scheme_malloc_code(long size)
 {
 #if defined(MZ_JIT_USE_MPROTECT) || defined(MZ_JIT_USE_WINDOWS_VIRTUAL_ALLOC)
+
   long size2, bucket, sz, page_size;
   void *p, *pg, *prev;
 
+# ifdef MZ_USE_PLACES
+  mzrt_mutex_lock(free_list_mutex);
+# endif
+
   if (size < CODE_HEADER_SIZE) {
     /* ensure CODE_HEADER_SIZE alignment 
        and room for free-list pointers */
@@ -891,44 +906,49 @@ void *scheme_malloc_code(long size)
     *(long *)pg = sz;
     LOG_CODE_MALLOC(1, printf("allocated large %p (%ld) [now %ld]\n", 
                               pg, size + CODE_HEADER_SIZE, scheme_code_page_total));
-    return ((char *)pg) + CODE_HEADER_SIZE;
+    p = ((char *)pg) + CODE_HEADER_SIZE;
   }
+  else {
+    bucket = free_list_find_bucket(size);
+    size2 = free_list[bucket].size;
 
-  bucket = free_list_find_bucket(size);
-  size2 = free_list[bucket].size;
-
-  if (!free_list[bucket].elems) {
-    /* add a new page's worth of items to the free list */
-    int i, count = 0;
-    pg = malloc_page(page_size);
-    scheme_code_page_total += page_size;
-    LOG_CODE_MALLOC(2, printf("new page for %ld / %ld at %p [now %ld]\n", 
-                              size2, bucket, pg, scheme_code_page_total));
-    sz = page_size - size2;
-    for (i = CODE_HEADER_SIZE; i <= sz; i += size2) {
-      p = ((char *)pg) + i;
-      prev = free_list[bucket].elems;
-      ((void **)p)[0] = prev;
-      ((void **)p)[1] = NULL;
-      if (prev)
-        ((void **)prev)[1] = p;
-      free_list[bucket].elems = p;
-      count++;
+    if (!free_list[bucket].elems) {
+      /* add a new page's worth of items to the free list */
+      int i, count = 0;
+      pg = malloc_page(page_size);
+      scheme_code_page_total += page_size;
+      LOG_CODE_MALLOC(2, printf("new page for %ld / %ld at %p [now %ld]\n", 
+            size2, bucket, pg, scheme_code_page_total));
+      sz = page_size - size2;
+      for (i = CODE_HEADER_SIZE; i <= sz; i += size2) {
+        p = ((char *)pg) + i;
+        prev = free_list[bucket].elems;
+        ((void **)p)[0] = prev;
+        ((void **)p)[1] = NULL;
+        if (prev)
+          ((void **)prev)[1] = p;
+        free_list[bucket].elems = p;
+        count++;
+      }
+      ((long *)pg)[0] = bucket; /* first long of page indicates bucket */
+      ((long *)pg)[1] = 0; /* second long indicates number of allocated on page */
+      free_list[bucket].count = count;
     }
-    ((long *)pg)[0] = bucket; /* first long of page indicates bucket */
-    ((long *)pg)[1] = 0; /* second long indicates number of allocated on page */
-    free_list[bucket].count = count;
+
+    p = free_list[bucket].elems;
+    prev = ((void **)p)[0];
+    free_list[bucket].elems = prev;
+    --free_list[bucket].count;
+    if (prev)
+      ((void **)prev)[1] = NULL;
+    ((long *)CODE_PAGE_OF(p))[1] += 1;
+
+    LOG_CODE_MALLOC(0, printf("allocated %ld (->%ld / %ld)\n", size, size2, bucket));
   }
 
-  p = free_list[bucket].elems;
-  prev = ((void **)p)[0];
-  free_list[bucket].elems = prev;
-  --free_list[bucket].count;
-  if (prev)
-    ((void **)prev)[1] = NULL;
-  ((long *)CODE_PAGE_OF(p))[1] += 1;
-  
-  LOG_CODE_MALLOC(0, printf("allocated %ld (->%ld / %ld)\n", size, size2, bucket));
+# ifdef MZ_USE_PLACES
+  mzrt_mutex_unlock(free_list_mutex);
+# endif
 
   return p;
 #else
@@ -943,6 +963,10 @@ void scheme_free_code(void *p)
   int per_page, n;
   void *prev;
 
+# ifdef MZ_USE_PLACES
+  mzrt_mutex_lock(free_list_mutex);
+# endif
+
   page_size = get_page_size();
 
   size = *(long *)CODE_PAGE_OF(p);
@@ -1015,6 +1039,10 @@ void scheme_free_code(void *p)
                               CODE_PAGE_OF(p), scheme_code_page_total));
     free_page(CODE_PAGE_OF(p), page_size);
   }
+# ifdef MZ_USE_PLACES
+  mzrt_mutex_unlock(free_list_mutex);
+# endif
+
 #else
   free(p);
 #endif
diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index c8ce7e868c..4f875eddf8 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -233,6 +233,7 @@ void scheme_init_dynamic_extension(Scheme_Env *env);
 #ifndef NO_REGEXP_UTILS
 extern void scheme_regexp_initialize(Scheme_Env *env);
 #endif
+void scheme_init_salloc(void);
 #ifdef MZ_USE_JIT
 void scheme_init_jit(void);
 #endif
@@ -2965,7 +2966,7 @@ void scheme_non_fixnum_result(const char *name, Scheme_Object *o);
 
 void scheme_raise_out_of_memory(const char *where, const char *msg, ...);
 
-extern unsigned long scheme_max_found_symbol_name;
+unsigned long scheme_get_max_symbol_length();
 
 char *scheme_make_arity_expect_string(Scheme_Object *proc,
 				      int argc, Scheme_Object **argv,
diff --git a/src/mzscheme/src/sstoinc.ss b/src/mzscheme/src/sstoinc.ss
index 627de6a98e..15dacd12a3 100644
--- a/src/mzscheme/src/sstoinc.ss
+++ b/src/mzscheme/src/sstoinc.ss
@@ -14,7 +14,7 @@
 	    [p (open-output-bytes)])
 	(write c p)
 	(let ([s (get-output-bytes p)])
-	  (printf "  {~n    static MZCOMPILED_STRING_FAR unsigned char expr[] = {")
+	  (printf "  {~n    SHARED_OK static MZCOMPILED_STRING_FAR unsigned char expr[] = {")
 	  (let loop ([chars (bytes->list s)][pos 0])
 	    (unless (null? chars)
 	      (let ([char (car chars)])
diff --git a/src/mzscheme/src/symbol.c b/src/mzscheme/src/symbol.c
index 15873003d5..53e725bdff 100644
--- a/src/mzscheme/src/symbol.c
+++ b/src/mzscheme/src/symbol.c
@@ -60,11 +60,11 @@ SHARED_OK mzrt_rwlock *symbol_table_lock;
 # define mzrt_rwlock_unlock(l) /* empty */
 #endif
 
-unsigned long scheme_max_found_symbol_name;
+SHARED_OK static unsigned long scheme_max_symbol_length;
 
 /* globals */
 SHARED_OK int scheme_case_sensitive = 1;
-static int gensym_counter; /*FIXME need atomic increment*/
+THREAD_LOCAL_DECL(static int gensym_counter);
 
 void scheme_set_case_sensitive(int v) { scheme_case_sensitive =  v; }
 
@@ -333,6 +333,12 @@ scheme_init_symbol (Scheme_Env *env)
   GLOBAL_IMMED_PRIM("gensym",                     gensym,                           0, 1, env);
 }
 
+unsigned long scheme_get_max_symbol_length() {
+  /* x86, x86_64, and powerpc support aligned_atomic_loads_and_stores */
+  return scheme_max_symbol_length;
+}
+
+
 static Scheme_Object *
 make_a_symbol(const char *name, unsigned int len, int kind)
 {
@@ -346,9 +352,13 @@ make_a_symbol(const char *name, unsigned int len, int kind)
   memcpy(sym->s, name, len);
   sym->s[len] = 0;
 
-  if (len > scheme_max_found_symbol_name) {
-    scheme_max_found_symbol_name = len;
+#ifdef MZ_USE_PLACES
+  mzrt_ensure_max_cas(&scheme_max_symbol_length, len);
+#else
+  if ( len > scheme_max_symbol_length ) {
+    scheme_max_symbol_length = len;
   }
+#endif
 
   return (Scheme_Object *) sym;
 }