xQueueGenericReceive function

orelavi wrote on Monday, April 07, 2008:


I don’t understand something in the xQueueGenericReceive function
( in queue.c file)

In this function there is this code:

   prvUnlockQueue( pxQueue );
   if( !xTaskResumeAll() )

My questions are:
How we can call to taskYIELD() function if there is an interrupt mask command above?
taskYIELD() function is a software interrupt so if the interrupts are disable how the YIELD can work?


rtel wrote on Monday, April 07, 2008:

This must be one of the most common questions, I don’t know why I have not added it to the FAQ :o)

Each port is designed to be able to yield from within an critical section - how it does this is port dependent.  If you look at the latest V4.8.0 code you will see that the lines you reference have actually been changed, although the yield from ISR is still used elsewhere.

Each task maintains its own critical section count - so when you yield to another task it is likely that the other task will have interrupts enabled.  Then when you return to the original task, when the task context is restored interrupts are disabled again so the task finds the interrupts in the state it expects to find them.