Differences between processes and threads in Linux and *BSD (i.e. OpenBSD)

[e1-531g]

Hello,
I have read blog post about processes and threads. I would like not to post link here, because this is not in English. It basically says that *BSD's processes and threads model at the lower layer are different than in example Linux kernel.
I would like to learn more, but I don't know where to search. I seek for information about differences between these kernels/operating systems, which are practical, pragmatic for somebody who wants to write some userspace programs, which will not be included in base of *BSDs. I would like to use this knowledge in C language.
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Added:
I don't want to mean that I don't actually know conceptual difference between process and thread. I seek differences in these two fields:
1. threads in Linux - threads in *BSDs
2. processes in Linux - processes in *BSDs

[jggimi]

I can speak, sparingly, to threads.

POSIX.1c, Threads Extensions (IEEE Std 1003.1c-1995) defined thread APIs, so if you use pthreads() there should not be a programmatic difference between POSIX-compliant operating systems, with the understanding that the supporting libraries and kernel syscalls may be very different.

But the BSDs do not all use the same technologies. And within a single BSD, the underlying services may change -- OpenBSD replaced its underlying thread technology in 2012. That new RThreads technology had been in development for seven years.

[ocicat]

Originally Posted by e1-531g

I seek for information about differences between these kernels/operating systems, which are practical, pragmatic for somebody who wants to write...

The definitive source is the source code itself.

While Linux has a much larger community where some books have been written (eg. Understanding the Linux Kernel), the closest tome from the BSD perspective is The Design and Implementation of the 4.4BSD Operating System.

Note that both books cited are dated.

The reason books on this subject are dated is because both the writing & the knowledge is tedious. While there is a market for such books, publishers are not excited on books such as this because the potential markets are small.

...& given that the implementations change, books on the subject quickly lose relevancy.

How developers & aspiring developers learn about these subjects in depth is simply to study the source code itself. There really is no shortcut.

[J65nko]

The latest edition of the Marshall Kirk McKusick book is from 2014, has 2 co-authors (George V. Neville-Neil and Robert N.M. Watson) and covers FreeBSD.
This edition is called The Design and Implementation of the FreeBSD Operating System.

I don't have the book, but according to the Amazon "Look inside", chapter IV covers processes and threads.

[ocicat]

Originally Posted by J65nko

The latest edition of the Marshall Kirk McKusick book is from 2014, has 2 co-authors (George V. Neville-Neil and Robert N.M. Watson) and covers FreeBSD.
This edition is called The Design and Implementation of the FreeBSD Operating System.

...& when this subject comes up on (repeatedly) on misc@, mention usually points out that for information on OpenBSD, going to the previous edition on 4.4BSD is more relevant.