HELP: Threads: strange behaiviour (???)

[Kamen Penev]

Perhaps his clock is not working.

Alex,  does the ticker sample work? If not, your clock support is broken 
and the executive will not timeslice.

Kamen

Joel Sherrill <joel at OARcorp.com> wrote:

> Alex wrote:
>
>> Hi,
>> I have a rtems program that launchs 2 extra threads. Each thread 
>> shares the same execution function.
>> Each thread, main included, uses the SCHED_RR with poriority 1.
>> The objective is to run the threads at the same time as possible 
>> sharing the time slice. In other words, I want to execute each thread 
>> in each quantum, so I choosed the SCHED_RR.
>>
>> What I get is the first extra thread running till the end and then 
>> the second extra thread begins execution.
>> Why both extra threads didn't start execution "at the same time?"
>>
>> The output I get is:
>>
>> ...
>> WAITING FOR SECONDARY THREADS
>>
>> secondary thread: beginning
>>
>> "some moments after..."
>>
>> secondary thread: finishing
>>
>> secondary thread: beginning
>>
>> "some moments after..."
>>
>> secondary thread: finishing
>> ...
>>
>>
>>
>> The output I expected was:
>>
>> ...
>> secondary thread: beginning
>> secondary thread: beginning
>>
>> "some moments after..."
>>
>> secondary thread: finishing
>> secondary thread: finishing
>> ...
>>
>> Do you agree with me?
>
>
> Maybe yes, maybe now. :)
>
> I think your secondary thread could be running to completion in less 
> than a timeslice.  Some things to try:
>
>   + Why status += in Task_1?
>   + Change the for in Task_1 to something that actually ensures it is
>     hanging around for at least 1 or 2 clock ticks.  Watch "current"
>     until it changes more than a timeslice.
>
> --joel
>
>> This is source code:
>>
>> #define CONFIGURE_INIT
>> #include <rtems.h>
>> #include <signal.h>
>> #include <rtems/posix/timer.h>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <errno.h>
>> #include <rtems/error.h>
>> #include <bsp.h>
>> #include <pthread.h>
>> #ifndef _POSIX_THREADS
>>     #error "rtems is supposed to have pthreads"
>> #endif
>>
>> #include <assert.h>
>> #include <string.h>
>> #include <time.h>
>> #include <unistd.h>
>> #include <time.h>
>> #include <sched.h>
>>
>>
>> void *Task_1(void *argument)
>> {
>>   int i=0;
>>   int status;
>>   struct timespec current;
>>
>>   puts("\nSecondary Thread: beginning" );
>>   for (i=0;i<100000000;i++)
>>   {
>>     status += clock_gettime( CLOCK_REALTIME, &current );
>>   }
>>
>>   puts("\nSecondary Thread: finishing" );
>>   pthread_exit( NULL );
>>   return NULL;
>> }
>>
>>
>> #define CONFIGURE_INIT_TASK_ENTRY_POINT   POSIX_Init
>> void POSIX_Init(void* args)
>> {
>>   const int MAX_THREADS     =10;
>>   const int n_number_of_counts     =10;  
>>   int             i=0;
>>   pthread_t            Task_ids[MAX_THREADS];
>>   pthread_t            Init_id;
>>   int                  status;
>>   pthread_attr_t       attr1;
>>   pthread_attr_t       attr2;
>>   struct sched_param      param;
>>  
>>   puts("\n\nSTARTING THE MAIN PROGRAM");
>>   Init_id = pthread_self();
>>   param.sched_priority = 1;
>>   status = pthread_setschedparam(Init_id, SCHED_RR, &param);
>>
>>   puts("\nCREATING THE SECONDARY THREADS");
>>     status = pthread_attr_init(&attr1);   if(status!=0)
>>   {
>>     puts("\n Error in pthread_attr_init1()");
>>     exit(1);
>>   }
>>   attr1.schedpolicy = SCHED_RR;
>>   attr1.schedparam.sched_priority = 1;
>>
>>   status = pthread_attr_init(&attr2);   if(status!=0)
>>   {
>>     puts("\n Error in pthread_attr_init1()");
>>     exit(1);
>>   }
>>   attr2.schedpolicy = SCHED_RR;
>>   attr2.schedparam.sched_priority = 1;
>>
>>
>>   status = pthread_create(&(Task_ids[0]),&attr1,Task_1,NULL);
>>   if(status!=0)
>>   {
>>     puts("\n Error in pthread_create1()");
>>     exit(1);
>>   }
>>
>>   status = pthread_create(&(Task_ids[1]),&attr2,Task_1,NULL);
>>   if(status!=0)
>>   {
>>     puts("\n Error in pthread_create2()");
>>     exit(1);
>>   }
>>
>>   puts("\nAFTER THREADS CREATION...\n");     puts( "\nWAITING FOR 
>> SECONDARY THREADS..." );
>>   status = pthread_join( Task_ids[0], NULL );
>>   if(status!=0)
>>   {
>>     puts("\n Error in pthread_join0()");
>>     exit(1);
>>   }
>>
>>   status = pthread_join( Task_ids[1], NULL );
>>   if(status!=0)
>>   {
>>     puts("\n Error in pthread_join1()");
>>     exit(1);
>>   }
>>
>>   puts("\nEND OF PROGRAM ***");
>>   exit(1);
>> }
>>
>>
>> #define CONFIGURE_MICROSECONDS_PER_TICK 1000  /*one milisecond per 
>> tick*/
>> #define CONFIGURE_TICKS_PER_TIMESLICE   1     /*each time slice runs 
>> for one milisecond*/
>> #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
>> #define CONFIGURE_POSIX_INIT_THREAD_TABLE
>> #define CONFIGURE_APPLICATION_NEEDS_CONSOLE_DRIVER
>> #define CONFIGURE_APPLICATION_NEEDS_CLOCK_DRIVER
>> #define CONFIGURE_MAXIMUM_TASKS                  20
>> #define CONFIGURE_MAXIMUM_POSIX_THREADS          20
>> #define CONFIGURE_MAXIMUM_SEMAPHORES             20
>> #define CONFIGURE_MAXIMUM_MESSAGE_QUEUES         20
>> #define CONFIGURE_MAXIMUM_POSIX_TIMERS          20
>> #define CONFIGURE_MAXIMUM_TIMERS          20
>> #define CONFIGURE_MAXIMUM_POSIX_QUEUED_SIGNALS      20
>> #define CONFIGURE_EXTRA_TASK_STACKS           (3 * 
>> RTEMS_MINIMUM_STACK_SIZE)
>> #include <confdefs.h>
>>
>>
>>
>>
>>
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>
>