Is Pthread library actually a user thread solution?

Question

The title might not be clear enough because I don\'t know how to define my questions actually.

I understand Pthread is a thread library meeting POSIX standard (about

Answer 1

I find previous answers not as satisfying or clear as I would have liked so here goes:

When you call

pthread_create(...)

you always create a new user-level thread. And assuming that there is OS, there is always one or more kernel thread...but let's dive deeper:

According to "Operating system concepts" 10th edition,the actual classification we should be looking at (when it comes to thread libraries) is how the user level threads are mapped onto kernel threads (and that's what the question really meant).

The models are one to one (each user-level thread within a single process is mapped to a different kernel thread),many to one (the thread library is "user level" so all of the different threads within a single process are mapped to a single kernel thread,and the threads data structures, context switch etc are dealt with at user level and not by the OS [meaning that if a thread blocks on some I/O call, the entire process might potentially block]), and many to many (something in between,obviously the number of user-level threads is greater or equal to the number of kernel threads it is being mapped onto).

Now,pthreads is a specification and not an implementation, and the implementation does depend on the OS to which it is written. It could be any one of those models (notice that "many to many" is very flexible).

So,as an example,on Linux and Windows (the most popular OSs for years now,where the model is "one to one") the implementation is "one to one".