有关Linux进程与线程数目计算的问题

问题的提出：

Linux,一个进程有n个线程，每个线程又使用fork（）创建了一个进程？

请问：总共有多少线程和进程？



问题的解答：




Alexander Amelkin • According to POSIX, after a fork() only the calling thread is to be cloned and all thread-related entities are not guaranteed to work (and in fact will NOT work). POSIX has a list of functions that are safe
to use after fork() and most of the thread-related functions aren't on that list. Actually, there is a good explanation given in the Rationale section of the fork() description in POSIX1. In a few words, it says that fork() in a threaded application is only
truly safe to use when it is almost immediately followed by exec().

Now, to answer your question. There will be your process with n threads plus n processes with 1 thread each. That totals n+1 processes and 2*n threads.



Yuri Perepechkin •http://pubs.opengroup.org/onlinepubs/009695399/functions/fork.html

fork - create a new process

A process shall be created with a single thread.

the new process shall contain a replica of the calling thread

Process/Threads:

* --fork-> 1/1

...

* --fork-> n-1/1

* --fork-> n/1

Total

processes: 1+n

threads: n+(n*1)=2n

Assumed each process must have one thread at least (main thread)

Start thread and process numeration from 1.

Daya Shanker Prasad •Thank you all,
for your answer. For a long time I used to think about it but couldn't pay time on this. Finally I experimented this and got:

Thread: 2n + 1

Process: n + 1

main() was running as separate thread which was forking n threads.