This example shows how our trace application runs and the results we will obtain.

    Consider this program, it uses NPTL functions we want to trace:
example.c

pthread_barrier_t bar;

pthread_t  th;

void function()
{ 
    printf("second thread before the barrier \n");

    pthread_barrier_wait(&bar);
   
    printf("second thread after the barrier \n");
}

int main()
{
    printf("main thread is beginning \n");

    pthread_barrier_init(&bar, NULL, 2);

    pthread_create(&th, NULL, fonction, NULL);

    pthread_barrier_wait(&bar);

    printf("main thread has finished \n");

    pthread_join(&th,NULL);

    pthread_barrier_destroy(&bar);
    return 0;
}




    In this program we use four Nptl functions:   pthread_barrier_init, pthread_create,  pthread_barrier_wait,  pthread_barrier_destroy.

It returns: "main thread is beginning"
                "second thread before the barrier"
                "second thread after the barrier"
                "main thread has finished"









The trace function will return us a text file like this:



1."Thread  0x40015360 initializes barrier 0x42130a14, lock= 0, left = 2 "     /*EVT_BARRIER_INIT*/


2."Thread  0x40015360 creates thread 0x51103287"          /*EVT_THREAD_INIT*/


3."Barrier 0x42130a14 is required by thread  0x40015360, lock = 0 " // EVT_BARRIER_LOCK_REQUIRE
 

4."Barrier 0x42130a14 is taken by thread  0x40015360, lock=1"  // EVT_BARRIER_LOCK_TAKEN


5."Thread  0x40015360  enters the barrier 0x42130a14, left =1 "     /*EVT_BARRIER_LEFT_DEC  */


6."Barrier 0x42130a14 is required by thread 0x51103287, lock = 1"     /* EVT_BARRIER_LOCK_REQUIRE*/


7."Thread: 0x51103287  is blocked"                                 /*EVT_THREAD_STATE_WAIT*/


7."Barrier 0x42130a14 is freed by thread 0x40015360 ,lock= 0"                         /* EVT_BARRIER_LOCK_FREE*/


8."Thread 0x51103287 is resumed"                                   /* EVT_THREAD_STATE_WAKE */


8."Barrier 0x42130a14 is taken by thread 0x51103287, lock= 0"     /* EVT_BARRIER_LOCK_TAKEN*/

 
9."Thread 0x40015360 is blocked"                         /*EVT_THREAD_STATE_WAIT*/


9."Thread 0x51103287 enters the barrier 0x42130a14, left = 0"     /*EVT_BARRIER_LEFT_DEC  */


10."Thread 0x51103287 leaves the barrier 0x42130a14, left = 1"   /* EVT_BARRIER_LEFT_INC*/


10."Thread 0x40015360 is resumed"                       /* EVT_THREAD_STATE_WAKE */


11."Thread  0x40015360 leaves the barrier 0x42130a14, left = 2"   /* EVT_BARRIER_LEFT_INC*/


11."Barrier 0x42130a14 is freed by thread 0x40015360  ,lock= 0"                  /* EVT_BARRIER_LOCK_FREE*/

12."Thread 0x40015360 is blocked"            /*EVT_THREAD_STATE_WAIT*/


13. " Thread 0x40015360 is resumed"            /* EVT_THREAD_STATE_WAKE */


14."Barrier0x42130a14 is required by thread  0x40015360, lock =0" // EVT_BARRIER_LOCK_REQUIRE
 

14."Thread 0x40015360 is blocked"                                 /*EVT_THREAD_STATE_WAIT*/


14."Thread 0x40015360 is waiting for thread 0x51103287"     /*EVT_THREAD_JOIN*/


15."Thread 0x40015360 is resumed"                       /* EVT_THREAD_STATE_WAKE */


16."Barrier 0x42130a14 is destroyed by thread 0x40015360, lock =1"  /* EVT_BARRIER_DESTROY*/



    Numbers at the beginning of each description represent the time, which is given by the computer clock.

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