Re: [ECOS] Alarms and Threads Program Problem :: Help Required

[Gary Thomas <gary at mlbassoc dot com>]

On Thu, 2005-08-18 at 22:09 +0530, R. Vamshi Krishna wrote:
> Hello,
> 
> I am trying to write a program that has 3 threads executing for 1,2,1 
> seconds each.
> These threads must each execute every 5,6,4 seconds respectively.
> 
> (Actually in Program I have multiplied these by a factor of 40 ).
> 
> I have tried the following program. One might expect the timing to get 
> screwed up, but
> actually the application hangs after saying the following :
> 
> "Thread 2A :: Time Before Execution is 1"
> hal_isr_default(33) : data (0)
> "Thread 2A :: Time After Execution is 27"
> "Thread 3 finished at :: 27"
> 
> Then I get something like
> $..thread .. and some weird numbers ...

This means that your code crashed and GDB is trying to tell you why.

> 
> PS : Note that  it is  Thread  3 that says it is finishing.

Which if you read your code, just means that thread 3's alarm went
off before it had a chance to actually execute.

> 
> Can someone tell me where am I going wrong ??
> 
> - Vamshi
> 
> Misc Data :
>     - Using Bitmap Scheduler
>     - Template is Kernel
>     - Turned Cache Off
>     - i386 Target with Realtek NIC card.

A few questions/observations:
  * Are you sure that the stack size of 4096 is adequate?  There are HAL
    defines for these which would be much safer to use.
  * Whenever you have a number of threads trying to print on the
    console, you can get scrambled results.  There are many ways around
    this, but if you want to print from DSR context (your alarm 
    functions run in DSR context), you'll need special protection.
  * Hard coding your loops, etc, is fraught with problems.  You can
    easily compute these things at runtime.

I made a few modifications to your code (none that changed your basic
code, just some improvements) and it runs just fine on my platform.
The modified version is attached - perhaps you want to try it.

Here are the first few lines of output:

Thread 1A :: Time Before Processing :: is 3
Thread 1A :: Time After Processing :: 44
Thread 2A :: Time Before Processing is 44 
Thread 2A :: Time After Processing is 125 
Thread 3A :: Time Before Processing is 126 
Thread 3A :: Time After Processing is 167 
Thread 1 finished at :: 203 
Thread 1A :: Time Before Processing :: is 203
Thread 1A :: Time After Processing :: 244
Thread 2 finished at :: 284 
Thread 2A :: Time Before Processing is 284 
Thread 3 finished at :: 286 
Thread 2A :: Time After Processing is 365 
Thread 3A :: Time Before Processing is 366 
Thread 1 finished at :: 403 
Thread 1A :: Time Before Processing :: is 403
Thread 1A :: Time After Processing :: 444
Thread 3 finished at :: 446 
Thread 3A :: Time After Processing is 450 
Thread 3A :: Time Before Processing is 450 
Thread 3A :: Time After Processing is 491 
Thread 2 finished at :: 524 
Thread 2A :: Time Before Processing is 524 
Thread 1 finished at :: 603 
Thread 1A :: Time Before Processing :: is 603
Thread 3 finished at :: 606 
Thread 1A :: Time After Processing :: 644
Thread 2A :: Time After Processing is 648 
Thread 3A :: Time Before Processing is 648 
Thread 3A :: Time After Processing is 689 

It kept running happily until I killed it.

Note that you're not getting exactly the thread behaviour
that you specified.  This is because of thread priorities
and preemptive scheduling.

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
------------------------------------------------------------

#include <cyg/kernel/kapi.h>

#include <stdio.h>
#include <stdlib.h>
#include <cyg/infra/diag.h>
#include <cyg/hal/hal_arch.h>

#define RVK 40


/*

	Thread Data-Structure for 3 threads.

*/

cyg_thread thread_s[3];




/*

	Stack Space for 3 threads

*/

char stack[3][CYGNUM_HAL_STACK_SIZE_TYPICAL];




/*

	Handles for threads.
	Also thread entry functions

*/

cyg_handle_t modeA_thread1, modeA_thread2, modeA_thread3;
cyg_thread_entry_t thread1A_entry, thread2A_entry, thread3A_entry;


/*

	Forward-Definition of functions

*/

void thread1A_alarm_func(cyg_handle_t, cyg_addrword_t);
void thread2A_alarm_func(cyg_handle_t, cyg_addrword_t);
void thread3A_alarm_func(cyg_handle_t, cyg_addrword_t);



/*

	Alarms and Counters related Data Structures

*/

cyg_handle_t thread_counter[3], system_clockH[3], thread_alarmH[3];
cyg_alarm thread_alarm[3];

void
safe_printf(char *fmt, ...)
{
    CYG_INTERRUPT_STATE old_intr;
    va_list ap;

    HAL_DISABLE_INTERRUPTS(old_intr);
    va_start(ap, fmt);
    diag_vprintf(fmt, ap);
    HAL_RESTORE_INTERRUPTS(old_intr);
}

int loops_per_tick;

void
init_loops_per_tick(void)
{
    int old_ticks, new_ticks;
    int j;

    if (loops_per_tick != 0) return;

    loops_per_tick = 0;
    old_ticks = (int) cyg_current_time();
    // Wait for time to roll
    while ((new_ticks = (int)cyg_current_time()) == old_ticks) ;
    // Now, see how many loops can happen before the next tick
    old_ticks = new_ticks;
    // Wait for time to roll
    while ((new_ticks = (int)cyg_current_time()) == old_ticks) {
        for (j = 0;  j < 10000;  j++) ;
        loops_per_tick++;
    }

    safe_printf("%d loops per tick\n", loops_per_tick);
}

/*

	Kernel Flags

*/

cyg_flag_t flag[3];


/*

	Starting the application.

*/


void cyg_user_start(void)
{


	/*

		Create 3 threads 1A, 2A, 3A .

	*/

	cyg_thread_create(3,thread1A_entry,(cyg_addrword_t) 0,"Mode A thread 1",
		 (void *) stack[0],CYGNUM_HAL_STACK_SIZE_TYPICAL,&modeA_thread1,&thread_s[0]);

	cyg_thread_create(4,thread2A_entry,(cyg_addrword_t) 0,"Mode A thread 2",
		 (void *) stack[1],CYGNUM_HAL_STACK_SIZE_TYPICAL,&modeA_thread2,&thread_s[1]);

	cyg_thread_create(5,thread3A_entry,(cyg_addrword_t) 0,"Mode A thread 3",
		 (void *) stack[2],CYGNUM_HAL_STACK_SIZE_TYPICAL,&modeA_thread3,&thread_s[2]);

	
	/*

		Intialize the Kernel Flags

	*/

	cyg_flag_init(&flag[0]);
	cyg_flag_init(&flag[1]);
	cyg_flag_init(&flag[2]);


	/*

		Initialize the alarms
		Period of each thread is (200/240/120) ticks of real-time clock.

	*/

	cyg_thread_resume(modeA_thread1);
	cyg_thread_resume(modeA_thread2);
	cyg_thread_resume(modeA_thread3);
}


void thread1A_entry(cyg_addrword_t data)
{	
    int i,j;

        init_loops_per_tick();
	system_clockH[0] = cyg_real_time_clock();
	cyg_clock_to_counter(system_clockH[0], &thread_counter[0]);

	cyg_alarm_create(thread_counter[0],thread1A_alarm_func,
		(cyg_addrword_t) 0,	&thread_alarmH[0], &thread_alarm[0]);

	cyg_alarm_initialize(thread_alarmH[0],cyg_current_time()+200,200);

	for(;;)
	{

		/*

			The following code executes for 40 ticks (approx) .
			This was determined experimentally.

		*/

		safe_printf("Thread 1A :: Time Before Processing :: is %u\n",
			(unsigned int) cyg_current_time());

		for(i=0;i<40*loops_per_tick;i++)
		{
			for(j=0;j<10000;j++)
			{
				;
			}
		}					



		safe_printf("Thread 1A :: Time After Processing :: %u\n",
			(unsigned int) cyg_current_time());
	
		/*

			Wait for Kernel Flag to Signal.

		*/
	
		cyg_flag_wait(&flag[0],0x1,
			CYG_FLAG_WAITMODE_AND | CYG_FLAG_WAITMODE_CLR);
	}
}


void thread2A_entry(cyg_addrword_t data)
{
	int i,j;

        init_loops_per_tick();
	system_clockH[1] = cyg_real_time_clock();
	cyg_clock_to_counter(system_clockH[1], &thread_counter[1]);

	cyg_alarm_create(thread_counter[1],thread2A_alarm_func,
		(cyg_addrword_t) 0, &thread_alarmH[1], &thread_alarm[1]);

	cyg_alarm_initialize(thread_alarmH[1],cyg_current_time()+240,240);

	for(;;)
	{
		/*
			The following code executes for 80 ticks (approx) .
			This was determined experimentally.
		*/

		safe_printf("Thread 2A :: Time Before Processing is %u \n",
			(unsigned int) cyg_current_time());

		for(i=0;i<80*loops_per_tick;i++)
		{
			for(j=0;j<10000;j++)
			{
				;
			}
		}

		safe_printf("Thread 2A :: Time After Processing is %u \n",				(unsigned int) cyg_current_time());

		/*
			Wait for Kernel Flag to Signal.
		*/

		cyg_flag_wait(&flag[1],0x1,
			CYG_FLAG_WAITMODE_AND | CYG_FLAG_WAITMODE_CLR);
	}
}



void thread3A_entry(cyg_addrword_t data)
{
	int i,j;

        init_loops_per_tick();
	system_clockH[2] = cyg_real_time_clock();
	cyg_clock_to_counter(system_clockH[2], &thread_counter[2]);

	cyg_alarm_create(thread_counter[2],thread3A_alarm_func,
		(cyg_addrword_t) 0, &thread_alarmH[2], &thread_alarm[2]);

	cyg_alarm_initialize(thread_alarmH[2],cyg_current_time()+160,160);
	
	for(;;)
	{

		/*
			The following code executes for 40 ticks (approx) .
			This was determined experimentally.
		*/

		safe_printf("Thread 3A :: Time Before Processing is %u \n",
			(unsigned int) cyg_current_time());

		for(i=0;i<40*loops_per_tick;i++)
		{
			for(j=0;j<10000;j++)
			{
				;
			}
		}

		safe_printf("Thread 3A :: Time After Processing is %u \n",
			(unsigned int) cyg_current_time());

		/*
	
			Wait for Kernel Flag to Signal.

		*/

		cyg_flag_wait(&flag[2],0x1,
			CYG_FLAG_WAITMODE_AND | CYG_FLAG_WAITMODE_CLR);

	}
}



/*
	Alarm-Handlers that suspend the various threads.
*/

void thread1A_alarm_func(cyg_handle_t alarm, cyg_addrword_t data)
{
	safe_printf("Thread 1 finished at :: %u \n",
		(unsigned int) cyg_current_time());

	cyg_flag_setbits(&flag[0], 0x1);
}



void thread2A_alarm_func(cyg_handle_t alarm, cyg_addrword_t data)
{
	safe_printf("Thread 2 finished at :: %u \n",
		(unsigned int) cyg_current_time());

	cyg_flag_setbits(&flag[1], 0x1);
}


void thread3A_alarm_func(cyg_handle_t alarm, cyg_addrword_t data)
{
	safe_printf("Thread 3 finished at :: %u \n",
		(unsigned int) cyg_current_time());

	cyg_flag_setbits(&flag[2], 0x1);
}


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