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//===-- sanitizer_persistent_allocator.h ------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// 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(®ion_pos, memory_order_acquire);
uptr end = atomic_load(®ion_end, memory_order_acquire);
if (cmp == 0 || cmp + size > end) return nullptr;
if (atomic_compare_exchange_weak(®ion_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(®ion_pos, 0, memory_order_relaxed);
uptr allocsz = 64 * 1024;
if (allocsz < size) allocsz = size;
uptr mem = (uptr)MmapOrDie(allocsz, "stack depot");
atomic_store(®ion_end, mem + allocsz, memory_order_release);
atomic_store(®ion_pos, mem, memory_order_release);
}
}
extern PersistentAllocator thePersistentAllocator;
inline void *PersistentAlloc(uptr sz) {
return thePersistentAllocator.alloc(sz);
}
} // namespace __sanitizer
#endif // SANITIZER_PERSISTENT_ALLOCATOR_H
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