Seventh chapter

POSIX Threads

Thread is light weight process.

Has the same address as the main thread (the thread that has created it).
Do not have to assign any stack. It will be allocated automatically.
Main thread can either wait or can create threads that will be wait by the OS. The OS will directly perform the cleanup
Thread immediately starts executing after it has been created. The execution depends on the scheduler. The thread will exit as soon as the main thread exits.
Threads can be created and stopped at run time.
Creation might involve some overhead. So the threads can be created at the initial stage, and can be woken up in-between or when needed. These are also called worker threads.
The mutex, conditional variable are some of the synchronisation functions to avoid corruption and parallel access to the same address space.
Standard GNU library provides POSIX thread implementation library. In linux there is no big difference between threads and processes as the overhead at creation and maintenance is mostly the same.
The threads will not appear in the ps command output. but ps -eLf would give all threads and processes running in the system.