Linux is a monolithic kernel. Device drivers and kernel extensions run in kernel space (ring 0 in many CPU architectures), with full access to the hardware, although some exceptions run in user space. The graphics system most people use with Linux doesn't run in the kernel, in contrast to that found in Microsoft Windows.
Kernel mode preemption allows device drivers to be preempted under certain conditions. This feature was added to handle hardware interrupts correctly and improve support for symmetric multiprocessing (SMP). Preemption also improves latency, increasing responsiveness and making Linux more suitable for real-time applications.