[BUG] xTaskGetTickCount() erroneously skips ahead

[AndrewSvatikDRS]

xTaskGetTickCount() erroneously skips ahead after every 65536 ticks. So when calculating timing using values returned by xTaskGetTickCount(), there are problems! vTaskDelay() has no problems. The problem is with xTaskGetTickCount()...

For example: Code:

TickType_t tickCount1, tickCount2;
while (1) {
    tickCount1 = xTaskGetTickCount();
    vTaskDelay(25);
    tickCount2 = xTaskGetTickCount();
    printf("[%ld] %lu ms have passed!\r\n",
            tickCount2, (tickCount2-tickCount1));
}

Output:

[64887] 25 ms have passed! [64912] 25 ms have passed! [64937] 25 ms have passed! [64962] 25 ms have passed! [66087] 1125 ms have passed! [66112] 25 ms have passed! [66137] 25 ms have passed! [66162] 25 ms have passed! [66187] 25 ms have passed!

Workaround is to use vTaskDelay() instead:

TickType_t tickCount = 0;
while (1) {
    vTaskDelay(25);
    tickCount += 25;
    printf("[%ld] %lu ms have passed!\r\n",
        xTaskGetTickCount(), tickCount);
}

PLATFORM: Microprocessor: STM32L496xx (ARM Cortex-M4) GNU Tools for STM32 (11.3.rel1) FreeRTOS API CMSIS v2 FreeRTOS version 10.3.1 CMSIS-RTOS version 2.00

[htibosch]

This looks very much like the issue reported on the FreeRTOS forum, and which is still "open".

Chances are very small that you have discovered a bug in the kernel that can be demonstrated so simply.

Please investigate the comments that you received and I am sure that you will find an explanation of the observed behaviour.

[aggarg]

Results on STM32H743ZI:

[64960] 25 ms have passed!
[64987] 25 ms have passed!
[65014] 25 ms have passed!
[65041] 25 ms have passed!
[65068] 25 ms have passed!
[65095] 25 ms have passed!
[65122] 25 ms have passed!
[65149] 25 ms have passed!
[65176] 25 ms have passed!
[65203] 25 ms have passed!
[65230] 25 ms have passed!
[65257] 25 ms have passed!
[65284] 25 ms have passed!
[65311] 25 ms have passed!
[65338] 25 ms have passed!
[65365] 25 ms have passed!
[65392] 25 ms have passed!
[65419] 25 ms have passed!
[65446] 25 ms have passed!
[65473] 25 ms have passed!
[65500] 25 ms have passed!
[65527] 25 ms have passed!
[65554] 25 ms have passed!
[65581] 25 ms have passed!
[65608] 25 ms have passed!
[65635] 25 ms have passed!
[65662] 25 ms have passed!
[65689] 25 ms have passed!
[65716] 25 ms have passed!
[65743] 25 ms have passed!
[65770] 25 ms have passed!
[65797] 25 ms have passed!
[65824] 25 ms have passed!
[65851] 25 ms have passed!
[65878] 25 ms have passed!
[65905] 25 ms have passed!
[65932] 25 ms have passed!
[65959] 25 ms have passed!
[65986] 25 ms have passed!
[66013] 25 ms have passed!
[66040] 25 ms have passed!
[66067] 25 ms have passed!
[66094] 25 ms have passed!
[66121] 25 ms have passed!
[66148] 25 ms have passed!
[66175] 25 ms have passed!
[66202] 25 ms have passed!

Lets continue the discussion on the forum.

[AndrewSvatikDRS]

This looks very much like the issue reported on the FreeRTOS forum, and which is still "open".

Chances are very small that you have discovered a bug in the kernel that can be demonstrated so simply.

Please investigate the comments that you received and I am sure that you will find an explanation of the observed behaviour.

Yes, I let myself become fooled. I wish I could delete this

[htibosch]

No Problem, the issue is now

Remember that 99% of our bugs are most probably caused by our own code. You're not the only one.

Wish you good luck with your projects.