arch_get_unmapped_area(struct file *filp, unsigned long addr,
		unsigned long len, unsigned long pgoff, unsigned long flags)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma, *prev;
	struct vm_unmapped_area_info info;
	const unsigned long mmap_end = arch_get_mmap_end(addr);

	if (len > mmap_end - mmap_min_addr)
		return -ENOMEM;

	if (flags & MAP_FIXED)
		return addr;

	if (addr) {
		addr = PAGE_ALIGN(addr);
		vma = find_vma_prev(mm, addr, &prev);
		if (mmap_end - len >= addr && addr >= mmap_min_addr &&
		    (!vma || addr + len <= vm_start_gap(vma)) &&
		    (!prev || addr >= vm_end_gap(prev)))
			return addr;
	}

	info.flags = 0;
	info.length = len;
	info.low_limit = mm->mmap_base;
	info.high_limit = mmap_end;
	info.align_mask = 0;
	return vm_unmapped_area(&info);
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.