Queue Data Struct

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Queue Data Struct

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sandrobastos
Contributor IV

Hello everybody,

I am trying to use Queue Data Struct in order to implement an alarm history.

The documentation is quite poor and there is not an example.

When I enqueue the second element, I get an 0x1d (29) error code that I could not find its mean anywhere.

After, for example, enqueue 10 elements, the queue size is correct (=10).

When I read the '_queue_head', that should be the first element enqueued, I get the last one (tail).

Then I keep going with '_queue_next' and all elements are the same, i.e. the last one (tail).

A simple code I implemented (based upon MFS code) just to test the feature:

#include <mqx.h>

#include <fio.h>

typedef struct _mfs_drive_struct

{

    uint32_t            DATA_START_SECTOR;

    QUEUE_STRUCT        HANDLE_LIST;

    uint32_t            FAT_TYPE;

} _MFS_DRIVE_STRUCT,    *_MFS_DRIVE_STRUCT_PTR;

/*

** file handle as defined by MFS

*/

typedef struct _mfs_handle

{

   QUEUE_ELEMENT_STRUCT   HEADER_PTR;

   long             LOCATION;

   long             SIZE;

   uint32_t         VALID;

} _MFS_HANDLE, * _MFS_HANDLE_PTR;

void _test_queue()

{

    _MFS_DRIVE_STRUCT ds;

    _MFS_DRIVE_STRUCT_PTR    drive_ptr=&ds;

    _MFS_HANDLE_PTR            handle;

    _MFS_HANDLE                hp, q_error;

    _MFS_HANDLE_PTR            handle_ptr=&hp;

    _MFS_HANDLE_PTR            next_handle;

    _queue_init(&drive_ptr->HANDLE_LIST, 0);

    for(int i = 0; i < 10; i++)

    {

        handle_ptr->SIZE = i*5;

        _queue_enqueue( &drive_ptr->HANDLE_LIST, (QUEUE_ELEMENT_STRUCT_PTR) handle_ptr);

        printf("erro=0x%02x\n", _queue_test   (&drive_ptr->HANDLE_LIST, (void*)&q_error));

    }

  

    next_handle =  (_MFS_HANDLE_PTR) _queue_head(&drive_ptr->HANDLE_LIST);

    printf("head: %d\n", next_handle->SIZE);

    while ( next_handle )

    {

        next_handle =  (_MFS_HANDLE_PTR) _queue_next(&drive_ptr->HANDLE_LIST, (QUEUE_ELEMENT_STRUCT_PTR) next_handle);

        printf("next: %d\n", next_handle->SIZE);

    }

}

bfac

karinavalencia

DavidSeymour

flaviocaduda

fernandaprata

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theJoel
Contributor III

Interesting. This is the MQX_CORRUPT_QUEUE error code.

Perhaps the _queue_enqueue cannot handle re-using the same element each time. The QUEUE_ELEMENT_STRUCT pointers are getting mangled in your for loop, here:

        _queue_enqueue( &drive_ptr->HANDLE_LIST, (QUEUE_ELEMENT_STRUCT_PTR) handle_ptr);


Can you make hp an array of 10 elements, and change handle_ptr = hp[i]; on each loop?


Cheers,

+Joel.

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theJoel
Contributor III

Hi Sandro,

I'm not sure your parameters for _queue_test() are correct.

you have:

_MFS_HANDLE              q_error;


_queue_test  (&drive_ptr->HANDLE_LIST, (void*)&q_error));


But the intent of the second parameter is to return a _pointer_ to the element in error, and not a copy of the full element. Try passing in the address of pointer type:


QUEUE_ELEMENT_STRUCT_PTR  q_error;


_queue_test(&drive_ptr->HANDLE_LIST, (void*)&q_error));



Hope this helps!

+Joel.


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sandrobastos
Contributor IV

Hi Joel,

Thanks for contributing.

Yes, you are right, it was a mistake but, unfortunately, it did not change the wrong behavior, I mean, it still returning 0x1d error and I just can read the tail element, not the others.

thank you and best regards,

Sandro

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theJoel
Contributor III

Interesting. This is the MQX_CORRUPT_QUEUE error code.

Perhaps the _queue_enqueue cannot handle re-using the same element each time. The QUEUE_ELEMENT_STRUCT pointers are getting mangled in your for loop, here:

        _queue_enqueue( &drive_ptr->HANDLE_LIST, (QUEUE_ELEMENT_STRUCT_PTR) handle_ptr);


Can you make hp an array of 10 elements, and change handle_ptr = hp[i]; on each loop?


Cheers,

+Joel.

View solution in original post

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sandrobastos
Contributor IV

Hi Joel and David,

I was trying to understand the David's approach when Joel unveiled the problem.

David, thank you very much for your help but I think MQX needs a better documentation - where are the error codes of '_queue_test()'? A little and silly example will be very appreciated to.

Joel, thank you for helping to understand the David's approach.

best regards,

Sandro

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DavidS
NXP Employee
NXP Employee

Hi Sandros,

I took a slightly different approach to work with queues and see how they are working.

I started with: C:\Freescale\Freescale_MQX_4_1_Vybrid\mqx\examples\test\test.c

Borrowed code from: C:\Freescale\Freescale_MQX_4_1_Vybrid\mqx\examples\lwevent\lwevent.c

Attached is my modified test.c and BSP/user_config.h.

I tested on my TWR-VF65GS10 Rev G tower kit with TWR-SER card so that I could use the DB-9 serial interface to my terminal utility.

I am using ARM DS5 IDE and lasted Vybrid MQX as path shows above.

The project is running test_twrvf65gs10_m4 on the Cortex M4 code and not the Cortex A5.

Each pass of the code will first call "      result = _lwevent_test(&error_ptr, &error2_ptr);" .

The test will check the lwevent queues so if you step into you can see that process.

The code will add lwevent as loop_cnt grows: if (_lwevent_create(&lwevent_array[loop_cnt],0) != MQX_OK)

Using DS5 I can see the OS Data Lightweight Events "Event Group*" grow as well.

After creating 11 new lwevents, the loop_cnt will decrement to 0 each loop and during that portion of the code we destroy lwevents.

Reference: if (_lwevent_destroy(&lwevent_array[loop_cnt]) != MQX_OK)

Stepping into the create and destroy code show how the queue process is being implemented.

Terminal Output:

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 0

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 1

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 2

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 3

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 4

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 5

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 6

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 7

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 8

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 9

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 10

_lwevent_test passed...    _lwevent_create passed...    All tests passed with loop_cnt = 10

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 9

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 8

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 7

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 6

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 5

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 4

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 3

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 2

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 1

_lwevent_test passed...    _lwevent_destroy passed...    All tests passed with loop_cnt = 0

Regards,

David