[Question]Question about the possibility of a problem in blk_mq_complete_remote.

[Manjong Lee]

Dear block layer developers.

While studying the block layer code, there is something I don't understand 
about the code.
It's hard to understand by myself. So I'd like to ask for your help.

I think the error can occur when the target cpu is changed to 
online -> offline during the ipi operation due to the request complete 
process below.

However, since the return value is not checked in the code,
it seems that a problem may occur.

So I wonder is this code the real problem or is there any other defense code?


Function path.

blk_mq_complete_request_remote
    blk_mq_complete_need_ipi  << Check if the cpu of rq is online
    blk_mq_complete_send_ipi  << Assume that the target cpu becomes offline here.
        smp_call_function_single_async 
            << send ipi to cpu and return -ENXIO if cpu is offline
               but it doesn't check the return value.