From 49ceb4d018f264bd4757df1ab3173d0760850af1 Mon Sep 17 00:00:00 2001
From: daan <daanl@outlook.com>
Date: Sun, 14 Jul 2019 16:48:53 -0700
Subject: [PATCH] refactor delayed_free code

---
 include/mimalloc-internal.h |  2 +-
 src/alloc.c                 | 14 +++++++++++++-
 src/page.c                  | 18 +++++-------------
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index a7f2f66d..3a3f5c4d 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -90,7 +90,7 @@ void*       _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t size) mi_at
 void*       _mi_heap_malloc_zero(mi_heap_t* heap, size_t size, bool zero);
 void*       _mi_heap_realloc_zero(mi_heap_t* heap, void* p, size_t newsize, bool zero);
 mi_block_t* _mi_page_ptr_unalign(const mi_segment_t* segment, const mi_page_t* page, const void* p);
-void        _mi_free_delayed_block(mi_page_t* page, mi_block_t* block);
+bool        _mi_free_delayed_block(mi_block_t* block);
 
 #if MI_DEBUG>1
 bool        _mi_page_is_valid(mi_page_t* page);
diff --git a/src/alloc.c b/src/alloc.c
index 6a5395c7..1c391e64 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -249,8 +249,20 @@ void mi_free(void* p) mi_attr_noexcept
   }
 }
 
-void _mi_free_delayed_block(mi_page_t* page, mi_block_t* block) {
+bool _mi_free_delayed_block(mi_block_t* block) {
+  // get segment and page
+  const mi_segment_t* segment = _mi_ptr_segment(block);
+  mi_assert_internal(_mi_ptr_cookie(segment) == segment->cookie);
+  mi_assert_internal(_mi_thread_id() == segment->thread_id);
+  mi_page_t* page = _mi_segment_page_of(segment, block);
+  if (mi_tf_delayed(page->thread_free) == MI_DELAYED_FREEING) {
+    // we might already start delayed freeing while another thread has not yet 
+    // reset the delayed_freeing flag; in that case don't free it quite yet if 
+    // this is the last block remaining.
+    if (page->used - page->thread_freed == 1) return false;
+  }
   _mi_free_block(page,true,block);
+  return true;
 }
 
 // Bytes available in a block
diff --git a/src/page.c b/src/page.c
index 9bc1ab87..fc7c4f01 100644
--- a/src/page.c
+++ b/src/page.c
@@ -139,8 +139,8 @@ void _mi_page_use_delayed_free(mi_page_t* page, mi_delayed_t delay  ) {
 static void mi_page_thread_free_collect(mi_page_t* page)
 {
   mi_block_t* head;
-  mi_thread_free_t tfree = 0;
-  mi_thread_free_t tfreex = 0;
+  mi_thread_free_t tfree;
+  mi_thread_free_t tfreex;
   do {
     tfreex = tfree = page->thread_free;
     head = mi_tf_block(tfree);
@@ -258,18 +258,10 @@ void _mi_heap_delayed_free(mi_heap_t* heap) {
   // and free them all
   while(block != NULL) {
     mi_block_t* next = mi_block_nextx(heap->cookie,block);
-    // get segment and page
-    const mi_segment_t* segment = _mi_ptr_segment(block);
-    mi_assert_internal(_mi_ptr_cookie(segment) == segment->cookie);
-    mi_assert_internal(_mi_thread_id() == segment->thread_id);
-    mi_page_t* page = _mi_segment_page_of(segment, block);
-    if (mi_tf_delayed(page->thread_free) != MI_DELAYED_FREEING) {
-      // use internal free instead of regular one to keep stats etc correct
-      _mi_free_delayed_block(page,block);
-    }
-    else {
+    // use internal free instead of regular one to keep stats etc correct
+    if (!_mi_free_delayed_block(block)) {
       // we might already start delayed freeing while another thread has not yet 
-      // reset the flag; in that case delay it further :-(
+      // reset the delayed_freeing flag; in that case delay it further by reinserting.
       mi_block_t* dfree;
       do {
         dfree = (mi_block_t*)heap->thread_delayed_free;