[External] Re: [PATCH] eal/linux: register mp hotplug callback after memory init

[Burakov, Anatoly]

On 6/2/2023 4:33 AM, 王志宏 wrote:
> Apologize that I have to go directly to function names to explain :)
>    - rte_eal_intr_init creates eal_intr_thread_main which starts 
> eal_intr_handle_interrupts
>    - rte_mp_channel_init creates mp_handle which processes messages 
> registered by rte_mp_action_register
>    - then, eal_mp_dev_hotplug_init calls rte_mp_action_register to 
> register handle_primary_request for EAL_DEV_MP_ACTION_REQUEST
> 
> At this point the whole messaging mechanism starts to function: When 
> primary attaches/detaches devices, it sends EAL_DEV_MP_ACTION_REQUEST, 
> and handle_primary_request invokes __handle_primary_request, which 
> calls local_dev_probe/remove. In the end it goes to for 
> example rte_eth_dev_attach_secondary.
> 
> Now, if secondary is somewhere after eal_mp_dev_hotplug_init but before 
> memory init done, it will crash due to memory access violation.
> 
> Thanks
> Zhihong

Hi,

I went into the code for IPC and you're right: we're only ignoring 
requests from *unregistered* callbacks, but if they were already 
registered, we handle them, which would cause your issue.

-- 
Thanks,
Anatoly