Interrupt handling in S state

[Prathibha Prakash]

Hi,in the demos ChibiOS/demos/various/RT-ARMCM4-USELIB it started the main thread then it sleep for some finite seconds.So when I looked at the sequence of actions taken,I can see a context switch occured..
chThdSleep --> chSysLock() --> chThdSleepS --> chSchGoSleepTimeoutS --> chSchGoSleepS --> chSysSwitch-->port switch..
So currently the stack pointer is at thread1 so it can't call unlock since the lock was taken by main thread and the system state is S.But in S state the regular interrupts are disabled,so how it will handle the interrupts without leaving the S state?

[Giovanni]

Hi,

Common question

Inside that sequence there is a context switch, the thread switched-in leaves the S-lock state on its side. The system never -stays- in S-lock state.

The sequence is always lock->switch->unlock, no delays inside.

Giovanni

[Prathibha Prakash]

But after context switch from main thread the pointer is at thread1 and it will start running it.Lock is taken from main so it should unlock it from main,so how to leave S-state??
main thread --> chSysLock --> Context switch(pointer at thread1 in S state) How to unlock from thread1?To unlock we need to return to main thread??

[Giovanni]

Hi,

I suggest you step by step through a context switch, this should make it clear.

Giovanni