# \<, or \<= ?? configMAX\_SYSCALL\_INTERRUPT\_PRIORITY 

**URL:** <https://forums.freertos.org/t/or-configmax-syscall-interrupt-priority/6131>\
**Category:** Kernel\
**Created:** [August 25, 2016, 2:32pm UTC](https://forums.freertos.org/t/or-configmax-syscall-interrupt-priority/6131 "2016-08-25T14:32:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dnadler](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/dnadler/32/35_2.png) [@dnadler](https://forums.freertos.org/u/dnadler)\
**Post date:** [August 25, 2016, 2:32pm UTC](https://forums.freertos.org/t/or-configmax-syscall-interrupt-priority/6131/1 "2016-08-25T14:32:44Z")

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**[dnadler](https://sourceforge.net/u/dnadler/)** wrote on [Thursday, August 25, 2016](https://sourceforge.net/p/freertos/discussion/382005/thread/f61aeb88/#d42f):

Hi Richard ! I got an assertion when I forgot to set an interrupt’s priority (thanks for that!).  
I set it to configMAX\_SYSCALL\_INTERRUPT\_PRIORITY and the code no longer asserts.  
However, the comments in FreeRTOS and documentation are approximately as follows:

```auto
  // ISRs using FreeRTOS APIs (for example, USB CDC driver uses FreeRTOS queues) must have priority
  // logically lower (numerically higher) than configMAX_SYSCALL_INTERRUPT_PRIORITY.
  // For an interrupt priority to be lower than configMAX_SYSCALL_INTERRUPT_PRIORITY,
  // it must be numerically higher than configMAX_SYSCALL_INTERRUPT_PRIORITY, because on the
  // ARM Cortex-M3 numerically low priority values represent logically high interrupt priorities.

```

Should the comments/documentation read “less than or equal to”?  
Or should the code be asserting if I do the following?  
NVIC\_SetPriority (USB\_IRQn, configMAX\_SYSCALL\_INTERRUPT\_PRIORITY);

Thanks as always,  
Best Regards, Dave

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<div class="post-metadata">

**Author:** ![rtel](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/rtel/32/31_2.png) [@rtel](https://forums.freertos.org/u/rtel)\
**Post date:** [August 25, 2016, 2:43pm UTC](https://forums.freertos.org/t/or-configmax-syscall-interrupt-priority/6131/2 "2016-08-25T14:43:55Z")

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**[rtel](https://sourceforge.net/u/rtel/)** wrote on [Thursday, August 25, 2016](https://sourceforge.net/p/freertos/discussion/382005/thread/f61aeb88/#d42f/cd69):

You are right, it should say less that or equal to.

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<div class="post-metadata">

**Author:** ![dnadler](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/dnadler/32/35_2.png) [@dnadler](https://forums.freertos.org/u/dnadler)\
**Post date:** [August 28, 2016, 4:13pm UTC](https://forums.freertos.org/t/or-configmax-syscall-interrupt-priority/6131/3 "2016-08-28T16:13:37Z")

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**[dnadler](https://sourceforge.net/u/dnadler/)** wrote on [Sunday, August 28, 2016](https://sourceforge.net/p/freertos/discussion/382005/thread/f61aeb88/#afce):

Thanks Richard!