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void  OSIntCtxSw (void)

Description

OSIntCtxSw() is  is called from from OSIntExit() to  to perform a context switch when all nested interrupts have returned.

Interrupts are disabled when when OSIntCtxSw() is  is called.

OSTCBCurPtr points  points at the the OS_TCB of  of the task that is switched out when when OSIntCtxSw() is  is called and and OSIntExit() sets  sets OSTCBHighRdyPtr to  to point at the the OS_TCB of  of the task that is switched in.

Files

os.h/os_cpu_a.asm

Prototype

Arguments

None

Returned Values

None

Required Configuration

None

Callers

OSIntExit().

Notes/Warnings

None

Example Usage

The pseudocode for OSIntCtxSw() is shown below. Notice that the code does only half of what OSCtxSw() did. The reason is that OSIntCtxSw() is called from an ISR and it is assumed that all of the CPU registers of the interrupted task were saved at the beginning of the ISR. OSIntCtxSw() therefore must only restore the context of the new, high-priority task.

(1) OSIntCtxSw() must call OSTaskSwHook().

(2) OSPrioHighRdy needs to be copied to OSPrioCur.

(3) OSTCBHighRdyPtr needs to be copied to OSTCBCurPtr because the current task will now be the new task.

(4) The stack pointer of the new task is restored from the OS_TCB of the new task.

(5) All the CPU registers need to be restored from the new task’s stack.

(6) A return from interrupt instruction must be executed.