Reduce the amount of locking in the kernel's memory region

The only thing here that really needs locking on malloc and free is
access to the allocation list, which is only used for TRACK_ALLOCATIONS.

Improves bench/task-perf-vector-party by 70%.

Author: brson

src/rt/memory_region.cpp

@@ -37,15 +37,13 @@ void memory_region::dec_alloc() {
 void memory_region::free(void *mem) {
     // printf("free: ptr 0x%" PRIxPTR" region=%p\n", (uintptr_t) mem, this);
     if (!mem) { return; }
-    if (_synchronized) { _lock.lock(); }
     alloc_header *alloc = get_header(mem);
     assert(alloc->magic == MAGIC);
     if (_live_allocations < 1) {
         _srv->fatal("live_allocs < 1", __FILE__, __LINE__, "");
     }
     release_alloc(mem);
     _srv->free(alloc);
-    if (_synchronized) { _lock.unlock(); }
 }
 
 void *
@@ -78,7 +76,6 @@ memory_region::realloc(void *mem, size_t size) {
 
 void *
 memory_region::malloc(size_t size, const char *tag, bool zero) {
-    if (_synchronized) { _lock.lock(); }
     size_t old_size = size;
     size += sizeof(alloc_header);
     alloc_header *mem = (alloc_header *)_srv->malloc(size);
@@ -91,7 +88,6 @@ memory_region::malloc(size_t size, const char *tag, bool zero) {
         memset(mem->data, 0, old_size);
     }
 
-    if (_synchronized) { _lock.unlock(); }
     return mem->data;
 }
 
@@ -145,6 +141,7 @@ memory_region::release_alloc(void *mem) {
     assert(alloc->magic == MAGIC);
 
 #ifdef TRACK_ALLOCATIONS
+    if (_synchronized) { _lock.lock(); }
     if (_allocation_list[alloc->index] != alloc) {
         printf("free: ptr 0x%" PRIxPTR " (%s) is not in allocation_list\n",
                (uintptr_t) &alloc->data, alloc->tag);
@@ -155,6 +152,7 @@ memory_region::release_alloc(void *mem) {
         _allocation_list[alloc->index] = NULL;
         alloc->index = -1;
     }
+    if (_synchronized) { _lock.unlock(); }
 #endif
     dec_alloc();
 }
@@ -164,7 +162,9 @@ memory_region::claim_alloc(void *mem) {
     alloc_header *alloc = get_header(mem);
     assert(alloc->magic == MAGIC);
 #ifdef TRACK_ALLOCATIONS
+    if (_synchronized) { _lock.lock(); }
     alloc->index = _allocation_list.append(alloc);
+    if (_synchronized) { _lock.unlock(); }
 #endif
     add_alloc();
 }