How are interrupts handled when program execution is in critical region?

Question

Below is the code of Sequencer function to register task.void UTIL_SEQ_RegTask(UTIL_SEQ_bm_t TaskId_bm, uint32_t Flags, void (*Task)( void ))
{
 UTIL_SEQ_ENTER_CRITICAL_SECTION();
 
 TaskCb[SEQ_BitPosition(TaskId_bm)] = Task;
 
 UTIL_SEQ_EXIT_CRITICAL_SECTION();
 
 return;
}Here, when the program execution is in critical region, i.e. when line 5 is being executed, what will happen if any interrupt occurs? Since, in critical region, interrupts are disabled, if any interrupts occur, then will those interrupts will be serviced after exiting the critical region or those interrupts will be missed?How do you guys handle this situation wherein you are in critical region and you get interrupt?Regards,noobmaster69

KnarfB · Answer

If a new interrupt arrives while it is disabled (e.g. in a critical section), the interrupt becomes pending. As soon as the interrupt is later enabled, it will be handled. Same for more than one different pending interrupt, all will be handled afterwards in prio order. The pending bit acts as a queue of depth 1. So, if the same interrupt arrives more than once during a critical section, it is only executed once afterwards, the other instances of the same interrupt are lost.

See "The Definitive Guide to the ARM Cortex..." books by Yoseph Yiu or the ARM Cortex... Prog Manuals.

hth

KnarfB

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