When configUSE_PREEMPTION is set to 1 and configUSE_TIME_SLICING to zero, the evaluation of the tasks priority is sometimes wrong and anyway not consistent:
xTaskIncrementTick :
if( pxTCB->uxPriority >= pxCurrentTCB->uxPriority )
vTaskPrioritySet:
if( uxNewPriority >= pxCurrentTCB->uxPriority )
vTaskResume, xTaskResumeFromISR:
if( pxTCB->uxPriority >= pxCurrentTCB->uxPriority )
xTaskGenericNotify ,xTaskGenericNotifyFromISR ,vTaskNotifyGiveFromISR,xTaskAbortDelay :
if( pxTCB->uxPriority > pxCurrentTCB->uxPriority )
So soemetimes it is checked for equality (wrong), sometimes not.
FreeRTOS Version 10.0.1