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AM3517: put_cred_rcu() sees d92cf5d8 with usage –1

Tim Gruijters
Prodigy 10 points
Part Number: AM3517
Other Parts Discussed in Thread: AM3505

Hi,

I have an AM3505 processor that runs a 4.19.96 kernel. I've disabled as much as debug configuration possible, but now I my regression framework is able to trigger the following kernel panic in two days (200~300 iterations):
[  318.159324] Kernel panic - not syncing: CRED: put_cred_rcu() sees d92cf5d8 with usage –1 
[  318.159324]  
[  318.168998] ---[ end Kernel panic - not syncing: CRED: put_cred_rcu() sees d92cf5d8 with usage –1 
[  318.168998]  ]--- 

elixir.bootlin.com/.../cred.c

If I enable CONFIG_DEBUG_CREDENTIALS, then the error does not happen. I'm already over a week of testing (1700 iterations).

I think this happens because adding debug brings latency to the kernel, but I'm wondering if somebody else seen and fixed this behaviour.

With kind regards,
Tim

  • 0
    TI__Guru* 87095 points

    Hello Tim,

    Please note that AM35x is an older part. The only knowledge source we have for this part is the collateral you can find on ti.com (e.g., the forums and the product page at https://www.ti.com/product/AM3505). We will be limited in the support we can offer since there is no EVM, etc for these parts. Also, the TI software for this part is too old for us to support. Since you are using Linux kernel 4.19, it must be a non-TI software release.

    Off the top of my head, I have not seen the behavior you observed on the other parts I have experience with. In general I point customers to our "Debugging an Embedded Linux System" training, but not sure if it is specific enough to help with your debug process:
    https://training.ti.com/debugging-embedded-linux-systems-training-series

    Regards,

    Nick