[libsanitizer merge from upstream r218156]

From-SVN: r215527

1 files changed, 69 insertions, 0 deletions

diff --git a/libsanitizer/sanitizer_common/sanitizer_persistent_allocator.h b/libsanitizer/sanitizer_common/sanitizer_persistent_allocator.h
new file mode 100644
index 00000000000..e29b7bd57aa
--- /dev/null
+++ b/libsanitizer/sanitizer_common/sanitizer_persistent_allocator.h
@@ -0,0 +1,69 @@
+//===-- sanitizer_persistent_allocator.h ------------------------*- C++ -*-===//
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A fast memory allocator that does not support free() nor realloc().
+// All allocations are forever.
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_PERSISTENT_ALLOCATOR_H
+#define SANITIZER_PERSISTENT_ALLOCATOR_H
+
+#include "sanitizer_internal_defs.h"
+#include "sanitizer_mutex.h"
+#include "sanitizer_atomic.h"
+#include "sanitizer_common.h"
+
+namespace __sanitizer {
+
+class PersistentAllocator {
+ public:
+  void *alloc(uptr size);
+
+ private:
+  void *tryAlloc(uptr size);
+  StaticSpinMutex mtx;  // Protects alloc of new blocks for region allocator.
+  atomic_uintptr_t region_pos;  // Region allocator for Node's.
+  atomic_uintptr_t region_end;
+};
+
+inline void *PersistentAllocator::tryAlloc(uptr size) {
+  // Optimisic lock-free allocation, essentially try to bump the region ptr.
+  for (;;) {
+    uptr cmp = atomic_load(&region_pos, memory_order_acquire);
+    uptr end = atomic_load(&region_end, memory_order_acquire);
+    if (cmp == 0 || cmp + size > end) return 0;
+    if (atomic_compare_exchange_weak(&region_pos, &cmp, cmp + size,
+                                     memory_order_acquire))
+      return (void *)cmp;
+  }
+}
+
+inline void *PersistentAllocator::alloc(uptr size) {
+  // First, try to allocate optimisitically.
+  void *s = tryAlloc(size);
+  if (s) return s;
+  // If failed, lock, retry and alloc new superblock.
+  SpinMutexLock l(&mtx);
+  for (;;) {
+    s = tryAlloc(size);
+    if (s) return s;
+    atomic_store(&region_pos, 0, memory_order_relaxed);
+    uptr allocsz = 64 * 1024;
+    if (allocsz < size) allocsz = size;
+    uptr mem = (uptr)MmapOrDie(allocsz, "stack depot");
+    atomic_store(&region_end, mem + allocsz, memory_order_release);
+    atomic_store(&region_pos, mem, memory_order_release);
+  }
+}
+
+extern PersistentAllocator thePersistentAllocator;
+inline void *PersistentAlloc(uptr sz) {
+  return thePersistentAllocator.alloc(sz);
+}
+
+} // namespace __sanitizer
+
+#endif  // SANITIZER_PERSISTENT_ALLOCATOR_H