STM32、FreeRTOS—— SVC 和 PendSV

最新推荐文章于 2025-06-03 01:45:26 发布

çheryアΔan

最新推荐文章于 2025-06-03 01:45:26 发布

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分类专栏： Free'RTOS

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问

I went through the xTaskStartSechudler() function, which ends up triggering the SVC instruction.
and i came to know that it used in only in this function.
If i am not wrong , is SVC used to launch the first Task ?
So, in my understanding SVC is used only one time, and subsequent task switching in and out is carried out in the PendSV handler. am i right ?
Why can cant we use pendsv itself instead of SVC ?

答

Yes you are correct, unless you are using the version that supports the
MPU the SVC instruction is only used once.

Old versions don’t use the SVC, and instead use the PendSV,
and there was a really good reason for changing that I can’t recall the exact details of but it was something to do with having to add extra code into the PendSV instruction so it knew whether it had to save a context or not, and also loosing a bit of stack space.
If you use SVC to start the first task then the SVC