During August 2025, Zbigniew Kempczynski contributed to the geerlingguy/linux repository by addressing a concurrency issue in the DRM Xe subsystem. He implemented a targeted fix for a race condition in the xe_sync driver, reordering ufence signaling to ensure it is marked as signalled before the memory write occurs. This approach prevented -EBUSY errors during map and unmap operations and enabled safe userspace reuse of ufences without synchronization issues. Working primarily in C, Zbigniew applied his expertise in kernel development and device drivers, demonstrating a deep understanding of low-level debugging and the intricacies of Linux kernel synchronization mechanisms.