[SOLVED] Multithreaded app using pth does not work

smeezekitty · 03-04-2010, 03:40 PM

I threw this togher based on the examples but the thread does not seem to run:

Code:

#include <stdio.h>
#include <pth.h>
static void *thread(void *arg){
 while(TRUE){
  printf("Thread\n");
 }
}
int main(){
 signal(SIGPIPE, SIG_IGN);
 long tick = 0;
 pth_attr_t attr;
 if(pth_init() == FALSE){printf("CANNOT INIT PTH");}
 attr = pth_attr_new();
 pth_attr_set(attr, PTH_ATTR_NAME, "thread");
 pth_attr_set(attr, PTH_ATTR_STACK_SIZE, 4096);
 pth_attr_set(attr, PTH_ATTR_JOINABLE, FALSE);
 if(pth_spawn(attr, thread, NULL) == NULL){printf("ERROR!");}
 while(tick < 65536){
  tick++;
  //fprintf(stderr, "Main\n");
 }
return 0;
}

It basically runs for ~750 ms and then terminates without a trace.

nadroj · 03-04-2010, 05:54 PM

First, I've never used or heard of this library until now. A quick search brings up

Quote:

Originally Posted by http://www.gnu.org/software/pth/pth-manual.html

In non-preemptive scheduling, once a thread received control from the scheduler it keeps it until either a blocking situation occurs (again a function call which would block and instead switches back to the scheduler) or the thread explicitly yields control back to the scheduler in a cooperative way.

When you create a thread using this library, that new thread doesn't have the chance to execute until one of the above mentioned events occur. In your program you create the thread but never let it execute. When you want it to execute, you can use "pth_yield", passing the "pth_t" returned by "pth_spawn" to let it execute.

Of course if you do this, then the program won't end due to the new thread being in an infinite loop. So you'll need to use signals or perform some blocking operation to let have the other thread ("main") continue. Also, you've declared "thread" to return "void*" but you don't return anything.

David1357 · 03-04-2010, 06:01 PM

Quote:

Originally Posted by smeezekitty

It basically runs for ~750 ms and then terminates without a trace.

Code:

    while(tick < 65536) {
        tick++;
        // Put a call to sleep here
        sleep(1);
    }

Put a call to sleep in the location shown above.

smeezekitty · 03-04-2010, 06:08 PM

Ok now its working, i put this line in both the main and threaded loop.

Code:

pth_nap(pth_time(0, 500));