Re: [PATCH v7] app/testpmd: monitor state of primary process when using secondary

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri,  8 Aug 2025 07:49:09 -0400
Khadem Ullah <14pwcse1224@uetpeshawar.edu.pk> wrote:

> The crashes are on 22.11, 23.03, 24.11, it is on all dpdk stable versions and 25.07 as well. 
> Please first close primary testpmd before secondary testpmd application 
> and try to close secondary or execute any of the following commands, 
> 
> "show device info all
> show port stats all 
> show port xstats all 
> set fwd rxonly 
> set fwd txonly 
> start
> etc"
> 
> We are all agree that these crashes exists. First we were tried 
> to prevent the crashes at PMD level, but it was not possible to 
> add checks in each PMD. Then we tried to add safety checks 
> in ethdev layer, and it was not suitable as with primary closing
> all reference to device information (pointers) would lead crashes.
> 
> Then we agreed on secondary process monitoring for primary process exiting. 
> and it is now resolved on application level, i.e. on testpmd. 
> 
> Now, this solution is working perfectly. We can add eal_cleanup for 
> gracefull exit. 
> 
> Best Regards, 
> Khadem 

Maybe this quick picture would help explain the data structures

                               │                                                 
                               │            Huge pages (shared)                                     
                               │                                                 
            rte_eth_devices[]  │                                                 
                               │                                                 
             ┌────────┐        │                                                 
Primary      │        ┼────────┼───┐                                             
Process      │        │        │   │                                             
             ┌────────┐        │   │                                             
             │        ┼────┐   │   │                                             
             │        │    │   │   │              rte_eth_dev_data               
             └────────┘    │   │   │            ┌─────────────────┐              
                           │   │   │            │                 │              
                           │   │   └───────────►│                 │              
                           │   │                │              ───┼─────────────►
                           │   │        ┌───────►                 │              
                           │   │        │       │                 │              
                           │   │        │       └─────────────────┘              
                           │   │        │                                        
                           │   │        │       ┌─────────────────┐              
                           │   │        │       │                 │              
                           └───┼────────┼───────►                 │              
                               │        │       │            ─────┼────────────► 
            rte_eth_devices    │        │  ┌────►                 │              
  Secondary ┌────────┐         │        │  │    │                 │              
  Process   │        ┼─────────┼────────┘  │    └─────────────────┘              
            │        │         │           │                                     
            ┌────────┐         │           │                                     
            │        ┼─────────┼───────────┘                                     
            │        │         │                                                 
            └────────┘         │                                                 
                               │