1 files changed, 37 insertions, 67 deletions

diff --git a/src/common/memarea.c b/src/common/memarea.c
index bcaea0949e..7d16b702e3 100644
--- a/src/common/memarea.c
+++ b/src/common/memarea.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2008-2013, The Tor Project, Inc. */
+/* Copyright (c) 2008-2016, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
 /** \file memarea.c
@@ -21,16 +21,19 @@
  * value. */
 #define MEMAREA_ALIGN SIZEOF_VOID_P
 
+/** A value which, when masked out of a pointer, produces a maximally aligned
+ * pointer. */
 #if MEMAREA_ALIGN == 4
-#define MEMAREA_ALIGN_MASK 3lu
+#define MEMAREA_ALIGN_MASK ((uintptr_t)3)
 #elif MEMAREA_ALIGN == 8
-#define MEMAREA_ALIGN_MASK 7lu
+#define MEMAREA_ALIGN_MASK ((uintptr_t)7)
 #else
 #error "void* is neither 4 nor 8 bytes long. I don't know how to align stuff."
 #endif
 
 #if defined(__GNUC__) && defined(FLEXIBLE_ARRAY_MEMBER)
 #define USE_ALIGNED_ATTRIBUTE
+/** Name for the 'memory' member of a memory chunk. */
 #define U_MEM mem
 #else
 #define U_MEM u.mem
@@ -61,7 +64,7 @@
 #endif
 
 /** Increment <b>ptr</b> until it is aligned to MEMAREA_ALIGN. */
-static INLINE void *
+static inline void *
 realign_pointer(void *ptr)
 {
   uintptr_t x = (uintptr_t)ptr;
@@ -80,15 +83,16 @@ typedef struct memarea_chunk_t {
   struct memarea_chunk_t *next_chunk;
   size_t mem_size; /**< How much RAM is available in mem, total? */
   char *next_mem; /**< Next position in mem to allocate data at.  If it's
-                   * greater than or equal to mem+mem_size, this chunk is
-                   * full. */
+                   * equal to mem+mem_size, this chunk is full. */
 #ifdef USE_ALIGNED_ATTRIBUTE
+  /** Actual content of the memory chunk. */
   char mem[FLEXIBLE_ARRAY_MEMBER] __attribute__((aligned(MEMAREA_ALIGN)));
 #else
   union {
     char mem[1]; /**< Memory space in this chunk.  */
     void *void_for_alignment_; /**< Dummy; used to make sure mem is aligned. */
-  } u;
+  } u; /**< Union used to enforce alignment when we don't have support for
+        * doing it right. */
 #endif
 } memarea_chunk_t;
 
@@ -105,56 +109,32 @@ struct memarea_t {
   memarea_chunk_t *first; /**< Top of the chunk stack: never NULL. */
 };
 
-/** How many chunks will we put into the freelist before freeing them? */
-#define MAX_FREELIST_LEN 4
-/** The number of memarea chunks currently in our freelist. */
-static int freelist_len=0;
-/** A linked list of unused memory area chunks.  Used to prevent us from
- * spinning in malloc/free loops. */
-static memarea_chunk_t *freelist = NULL;
-
 /** Helper: allocate a new memarea chunk of around <b>chunk_size</b> bytes. */
 static memarea_chunk_t *
-alloc_chunk(size_t sz, int freelist_ok)
+alloc_chunk(size_t sz)
 {
   tor_assert(sz < SIZE_T_CEILING);
-  if (freelist && freelist_ok) {
-    memarea_chunk_t *res = freelist;
-    freelist = res->next_chunk;
-    res->next_chunk = NULL;
-    --freelist_len;
-    CHECK_SENTINEL(res);
-    return res;
-  } else {
-    size_t chunk_size = freelist_ok ? CHUNK_SIZE : sz;
-    memarea_chunk_t *res;
-    chunk_size += SENTINEL_LEN;
-    res = tor_malloc(chunk_size);
-    res->next_chunk = NULL;
-    res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
-    res->next_mem = res->U_MEM;
-    tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
-               ((char*)res)+chunk_size);
-    tor_assert(realign_pointer(res->next_mem) == res->next_mem);
-    SET_SENTINEL(res);
-    return res;
-  }
+
+  size_t chunk_size = sz < CHUNK_SIZE ? CHUNK_SIZE : sz;
+  memarea_chunk_t *res;
+  chunk_size += SENTINEL_LEN;
+  res = tor_malloc(chunk_size);
+  res->next_chunk = NULL;
+  res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
+  res->next_mem = res->U_MEM;
+  tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
+             ((char*)res)+chunk_size);
+  tor_assert(realign_pointer(res->next_mem) == res->next_mem);
+  SET_SENTINEL(res);
+  return res;
 }
 
-/** Release <b>chunk</b> from a memarea, either by adding it to the freelist
- * or by freeing it if the freelist is already too big. */
+/** Release <b>chunk</b> from a memarea. */
 static void
-chunk_free_unchecked(memarea_chunk_t *chunk)
+memarea_chunk_free_unchecked(memarea_chunk_t *chunk)
 {
   CHECK_SENTINEL(chunk);
-  if (freelist_len < MAX_FREELIST_LEN) {
-    ++freelist_len;
-    chunk->next_chunk = freelist;
-    freelist = chunk;
-    chunk->next_mem = chunk->U_MEM;
-  } else {
-    tor_free(chunk);
-  }
+  tor_free(chunk);
 }
 
 /** Allocate and return new memarea. */
@@ -162,7 +142,7 @@ memarea_t *
 memarea_new(void)
 {
   memarea_t *head = tor_malloc(sizeof(memarea_t));
-  head->first = alloc_chunk(CHUNK_SIZE, 1);
+  head->first = alloc_chunk(CHUNK_SIZE);
   return head;
 }
 
@@ -174,7 +154,7 @@ memarea_drop_all(memarea_t *area)
   memarea_chunk_t *chunk, *next;
   for (chunk = area->first; chunk; chunk = next) {
     next = chunk->next_chunk;
-    chunk_free_unchecked(chunk);
+    memarea_chunk_free_unchecked(chunk);
   }
   area->first = NULL; /*fail fast on */
   tor_free(area);
@@ -190,26 +170,13 @@ memarea_clear(memarea_t *area)
   if (area->first->next_chunk) {
     for (chunk = area->first->next_chunk; chunk; chunk = next) {
       next = chunk->next_chunk;
-      chunk_free_unchecked(chunk);
+      memarea_chunk_free_unchecked(chunk);
     }
     area->first->next_chunk = NULL;
   }
   area->first->next_mem = area->first->U_MEM;
 }
 
-/** Remove all unused memarea chunks from the internal freelist. */
-void
-memarea_clear_freelist(void)
-{
-  memarea_chunk_t *chunk, *next;
-  freelist_len = 0;
-  for (chunk = freelist; chunk; chunk = next) {
-    next = chunk->next_chunk;
-    tor_free(chunk);
-  }
-  freelist = NULL;
-}
-
 /** Return true iff <b>p</b> is in a range that has been returned by an
  * allocation from <b>area</b>. */
 int
@@ -237,16 +204,19 @@ memarea_alloc(memarea_t *area, size_t sz)
   tor_assert(sz < SIZE_T_CEILING);
   if (sz == 0)
     sz = 1;
-  if (chunk->next_mem+sz > chunk->U_MEM+chunk->mem_size) {
+  tor_assert(chunk->next_mem <= chunk->U_MEM + chunk->mem_size);
+  const size_t space_remaining =
+    (chunk->U_MEM + chunk->mem_size) - chunk->next_mem;
+  if (sz > space_remaining) {
     if (sz+CHUNK_HEADER_SIZE >= CHUNK_SIZE) {
       /* This allocation is too big.  Stick it in a special chunk, and put
        * that chunk second in the list. */
-      memarea_chunk_t *new_chunk = alloc_chunk(sz+CHUNK_HEADER_SIZE, 0);
+      memarea_chunk_t *new_chunk = alloc_chunk(sz+CHUNK_HEADER_SIZE);
       new_chunk->next_chunk = chunk->next_chunk;
       chunk->next_chunk = new_chunk;
       chunk = new_chunk;
     } else {
-      memarea_chunk_t *new_chunk = alloc_chunk(CHUNK_SIZE, 1);
+      memarea_chunk_t *new_chunk = alloc_chunk(CHUNK_SIZE);
       new_chunk->next_chunk = chunk;
       area->first = chunk = new_chunk;
     }