How does the CONFIG_PREEMPT_RT patch work?
The RT-Preempt patch converts Linux into a fully preemptible kernel. The magic is done with: • Making in-kernel locking-primitives (using spinlocks) preemptible though reimplementation with rtmutexes. • Critical sections protected by i.e. spinlock_t and rwlock_t are now preemptible. The creation of non-preemptible sections (in kernel) is still possible with raw_spinlock_t (same APIs like spinlock_t). • Implementing priority inheritance for in-kernel spinlocks and semaphores. For more information on priority inversion and priority inheritance please consult Introduction to Priority Inversion. • Converting interrupt handlers into preemptible kernel threads: The RT-Preempt patch treats soft interrupt handlers in kernel thread context, which is represented by a task_struct like a common user space process. However it is also possible to register an IRQ in kernel context. • Converting the old Linux timer API into separate infrastructures for high resolution kernel timers plus one for timeou
