Keith Owens wrote:
> mca_handler_bh() is running as an extension of the MCA event which
> means that it is not irq safe.  It is not safe to get any external lock
> in mca_page_isolate() or mca_handler_bh().

Therefore the MCA handler couldn't recover the system if the process is
running in kernel-mode since it possibly has such important kernel locks.

> AFAICT, my concerns about the MCA event and mca_handler_bh() not being
> irq safe are only a problem for the case when the MCA was triggered by
> user space code but was delivered when the cpu was in kernel code.
> Maybe we do not support the problem case.
> 
> *    offending process  affected process  OS MCA do
> *     kernel mode        kernel mode       down system
> *     kernel mode        user   mode       kill the process
> *     user   mode        kernel mode       kill the process <=== problem
> *     user   mode        user   mode       kill the process

So we have to guarantee that the process is running in user-mode,
which all processes can't have any locks of kernel, right?

It would be happy if this fixed patch satisfy your requirement.

Thanks,
H.Seto