On Thu, Jun 19, 2014 at 07:39:42AM +0000, Tony Lu wrote:
> Hi
>
> I got the below output that shows perf can not resolve symbols for
> forked threads. I did a system-wide collection from all CPUs after the
> application hello run.
There's no fork() in... :-)
> #include <pthread.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #define NUM_THREADS 5
>
> void foo(void)
> {
> long i = 1000000000;
> while (i--) {
> ;
> }
> }
>
> void *PrintHello(void *threadid)
> {
> long tid;
> tid = (long)threadid;
> printf("Hello World! It's me, thread #%ld!\n", tid);
> foo();
> pthread_exit(NULL);
> }
>
> int main(int argc, char *argv[])
> {
> pthread_t threads[NUM_THREADS];
> int rc;
> long t;
> for(t=0;t<NUM_THREADS;t++){
> printf("In main: creating thread %ld\n", t);
> rc = pthread_create(&threads[t], NULL, PrintHello, (void *)t);
> if (rc){
> printf("ERROR; return code from pthread_create() is %d\n", rc);
> exit(-1);
> }
> }
>
> /* Last thing that main() should do */
> pthread_exit(NULL);
> }
That pthread_exit() is the problem; this results in:
29456 pts/23 Zl 0:00 | \_ [hello] <defunct>
You want to wait for the threads to complete using pthread_join().
I suspect the defunct state hides the process.
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