Clangformat and Concurrency Safety.

Author: mjp41

src/backend/backend.h

@@ -303,8 +303,8 @@ namespace snmalloc
       return {p, meta};
     }
 
-    static void dealloc_chunk(
-      LocalState& local_state, MetaCommon& meta_common, size_t size)
+    static void
+    dealloc_chunk(LocalState& local_state, MetaCommon& meta_common, size_t size)
     {
       auto chunk = meta_common.chunk;
 

src/backend/commitrange.h

@@ -25,6 +25,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = ParentRange::Aligned;
 
+    static constexpr bool ConcurrencySafe = ParentRange::ConcurrencySafe;
+
     constexpr CommitRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/decayrange.h

@@ -50,7 +50,7 @@ namespace snmalloc
       {
         auto next = get_next();
 
-        f (curr.get_capability());
+        f(curr.get_capability());
 
         curr = next;
       }
@@ -120,6 +120,12 @@ namespace snmalloc
     }
   };
 
+  /**
+   * This range slowly filters back memory to the parent range.
+   * It locally caches memory and after it hasn't been used for some time
+   * it goes back to its parent range.
+   */
+
   template<typename ParentRange, typename PAL, typename Pagemap>
   class DecayRange
   {
@@ -173,16 +179,21 @@ namespace snmalloc
 
     static void handle_decay_tick()
     {
-      auto new_epoch = (epoch + 1) % NUM_EPOCHS;
+      static_assert(
+        ParentRange::ConcurrencySafe,
+        "Parent must be concurrency safe, as dealloc_range is called here on "
+        "potentially another thread's state.");
+      auto new_epoch =
+        (epoch + 1) % NUM_EPOCHS;
       // Flush old index for all threads.
       auto curr = all_local.load(std::memory_order_acquire);
       while (curr != nullptr)
       {
         for (size_t sc = 0; sc < NUM_SLAB_SIZES; sc++)
         {
           auto old_stack = curr->chunk_stack[sc][new_epoch].pop_all();
-          
-          old_stack.forall([curr, sc](auto cap){
+
+          old_stack.forall([curr, sc](auto cap) {
             curr->parent->dealloc_range(cap, MIN_CHUNK_SIZE << sc);
           });
         }
@@ -228,6 +239,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = ParentRange::Aligned;
 
+    static constexpr bool ConcurrencySafe = false;
+
     constexpr DecayRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/empty_range.h

@@ -19,6 +19,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = true;
 
+    static constexpr bool ConcurrencySafe = true;
+
     constexpr EmptyRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t)

src/backend/globalrange.h

@@ -37,6 +37,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = ParentRange::Aligned;
 
+    static constexpr bool ConcurrencySafe = true;
+
     constexpr GlobalRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/largebuddyrange.h

@@ -271,6 +271,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = true;
 
+    static constexpr bool ConcurrencySafe = false;
+
     constexpr LargeBuddyRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/pagemapregisterrange.h

@@ -30,6 +30,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = ParentRange::Aligned;
 
+    static constexpr bool ConcurrencySafe = ParentRange::ConcurrencySafe;
+
     capptr::Chunk<void> alloc_range(size_t size)
     {
       auto base = state->alloc_range(size);

src/backend/palrange.h

@@ -24,6 +24,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = pal_supports<AlignedAllocation, PAL>;
 
+    static constexpr bool ConcurrencySafe = true;
+
     constexpr PalRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/smallbuddyrange.h

@@ -175,6 +175,8 @@ namespace snmalloc
     static constexpr bool Aligned = true;
     static_assert(ParentRange::Aligned, "ParentRange must be aligned");
 
+    static constexpr bool ConcurrencySafe = false;
+
     constexpr SmallBuddyRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)

src/backend/statsrange.h

@@ -31,6 +31,8 @@ namespace snmalloc
 
     static constexpr bool Aligned = ParentRange::Aligned;
 
+    static constexpr bool ConcurrencySafe = ParentRange::ConcurrencySafe;
+
     constexpr StatsRange() = default;
 
     capptr::Chunk<void> alloc_range(size_t size)