From 261b7bde28b8c46191a7fb7ad83cec10ccd5135d Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 8 Sep 2015 15:27:46 -0600
Subject: [PATCH] set-phantom-bytes!: fix tracking across generations

---
 racket/src/racket/gc2/gc2.h    |  4 ++--
 racket/src/racket/gc2/newgc.c  | 15 ++++++++++++---
 racket/src/racket/src/thread.c |  4 ++--
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/racket/src/racket/gc2/gc2.h b/racket/src/racket/gc2/gc2.h
index 84e6cfb3a9..307ab2c48c 100644
--- a/racket/src/racket/gc2/gc2.h
+++ b/racket/src/racket/gc2/gc2.h
@@ -277,10 +277,10 @@ GC2_EXTERN int GC_is_on_allocated_page(void *p);
    the GC allocates objects (although p may or may not
    be a valid pointer to the start of an alloctaed object). */
 
-GC2_EXTERN int GC_allocate_phantom_bytes(intptr_t);
+GC2_EXTERN int GC_allocate_phantom_bytes(void *pb, intptr_t);
 /* 
    Returns 0 if allocation should fail due to a memory limit, 
-   1 otherwise. */
+   1 otherwise. The representative `pb` determines who is charged. */
 
 /***************************************************************************/
 /* Memory tracing                                                          */
diff --git a/racket/src/racket/gc2/newgc.c b/racket/src/racket/gc2/newgc.c
index 71965eeeb6..ba710c56c9 100644
--- a/racket/src/racket/gc2/newgc.c
+++ b/racket/src/racket/gc2/newgc.c
@@ -1656,9 +1656,10 @@ uintptr_t add_no_overflow(uintptr_t a, uintptr_t b)
   return c;
 }
 
-int GC_allocate_phantom_bytes(intptr_t request_size_bytes)
+int GC_allocate_phantom_bytes(void *pb, intptr_t request_size_bytes)
 {
   NewGC *gc = GC_get_GC();
+  mpage *page;
 
 #ifdef NEWGC_BTC_ACCOUNT
   if (request_size_bytes > 0) {
@@ -1674,14 +1675,22 @@ int GC_allocate_phantom_bytes(intptr_t request_size_bytes)
     /* overflow */
     return 1;
 
-  gc->gen0_phantom_count += request_size_bytes;
+  page = pagemap_find_page(gc->page_maps, pb);
+
   /* adjust `gc->memory_in_use', but protect against {over,under}flow: */
   if (request_size_bytes < 0) {
     request_size_bytes = -request_size_bytes;
     if (gc->memory_in_use > request_size_bytes)
       gc->memory_in_use -= request_size_bytes;
-  } else
+    if (!page || (page->generation != AGE_GEN_1)) {
+      if (gc->gen0_phantom_count > request_size_bytes)
+        gc->gen0_phantom_count -= request_size_bytes;
+    }
+  } else {
+    if (!page || (page->generation != AGE_GEN_1))
+      gc->gen0_phantom_count = add_no_overflow(gc->gen0_phantom_count, request_size_bytes);
     gc->memory_in_use = add_no_overflow(gc->memory_in_use, request_size_bytes);
+  }
 
   /* If we've allocated enough phantom bytes, then force a GC */
   if (gc->gen0_phantom_count > GEN0_MAX_SIZE)
diff --git a/racket/src/racket/src/thread.c b/racket/src/racket/src/thread.c
index 7f47807b87..7ef4c0db43 100644
--- a/racket/src/racket/src/thread.c
+++ b/racket/src/racket/src/thread.c
@@ -8309,7 +8309,7 @@ static Scheme_Object *make_phantom_bytes(int argc, Scheme_Object *argv[])
   pb->size = SCHEME_INT_VAL(argv[0]);
 
 # ifdef MZ_PRECISE_GC
-  if (!GC_allocate_phantom_bytes(pb->size))
+  if (!GC_allocate_phantom_bytes(pb, pb->size))
     scheme_raise_out_of_memory("make-phantom-bytes", NULL);
 # endif
 
@@ -8330,7 +8330,7 @@ static Scheme_Object *set_phantom_bytes(int argc, Scheme_Object *argv[])
   amt = SCHEME_INT_VAL(argv[1]);
 
 # ifdef MZ_PRECISE_GC
-  if (!GC_allocate_phantom_bytes(amt - pb->size))
+  if (!GC_allocate_phantom_bytes(pb, amt - pb->size))
     scheme_raise_out_of_memory("make-phantom-bytes", NULL);
 # endif