|WP1 - RTOS State of the Art Analysis: Deliverable D1.1 - RTOS Analysis|
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Current Linux implementation of POSIX threads (POSIX 1003.1c) is based on the work done by Xavier Leroy, known as LinuxThreads. LinuxThreads is now integrated in the glibc, and distributed as a part of the it. It provides kernel-level threads: threads are created with the clone() system call and all scheduling is done in the kernel. This kind of threading is defined as 1:1, i.e. each thread is mapped to a Linux process.
LinuxThreads implements most of the POSIX API: mutex, condition variables, cancellation, signals, timed calls, etc. The library also provides POSIX semaphores. Mutex do not implement any protocol to prevent priority inversion. Since threads are scheduled by the Linux scheduler, the scheduling policies are the same as in Linux: SCHED_FIFO, SCHED_RR and SCHED_OTHER.