Programming

Hello
Is there a way to get the no. of threads spawned by a program in C?
There is no function in pthread.h that does this.

Hi,
This is totally OS dependent. In think WIndows allow 1024 threads.

Do you want to know how many threads a process is allowed to create?
If that's the case then on AIX sysconf(_SC_THREAD_THREADS_MAX) will tell you the max number of threads allowed within a process.

I think the OP wants to now how many threads an application has created, not the maximiun possible.

It is generally possible to determine the number of threads from within a C program. However, how it is done is very OS-specific. If you tell us your platform and OS version, somebody here on this forum should be able to help you.

Thats not what I am looking for. I have written a C program that spawns posix threads using pthread_create. I want to programmatically get the no. of threads spawned by the program at some instance of time in the program. There is no function in pthread.h that does this. So I was wondering if there is a way to do it.


I am running my program on a Linux box that runs OpenSUSE 11.

In that case it only depends on how you go about creating threads within your C program especially if threads create other threads using nested function calls.

If you call pthread_create in a master thread or main program it is easy. This sit eh total numbers of threads created, not currently active threads

Code:

int thread_count=0;
...................
if(pthread_create(.....) == 0) thread_count++;

If "everybody" creates a thread, then you need to create a static mutex then a static integer variable in shared memory, initialize it to zero. Everybody calling pthread_create does this:

Code:

wait on mutex
get mutex & add one to the global counter;
release the mutex

pthreads have these basic calls (plus a lot of others)

Code:

create & destroy a mutex
      pthread_mutex_init(),
      pthread_mutex_destroy()
      PTHREAD_MUTEX_INITIALIZER is a macro to create a static mutex - probably what you want.

Lock/unlock a mutex.      

      pthread_mutex_lock(),
      pthread_mutex_trylock(),
      pthread_mutex_unlock()

that lets you play with mutexes. You will have to pass the mutex address to all of your threads or they cannot use it.