Re: [dpdk-dev] eal: DPDK: 18.11.6 version rte_eal_init() function cleans the runtime directory in 5.4.35 kernel

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 15-Oct-20 5:14 PM, Mohakud, Amiya Ranjan wrote:
> + Souvik
> 
> *From:*Mohakud, Amiya Ranjan
> *Sent:* 15 October 2020 21:38
> *To:* Burakov, Anatoly <anatoly.burakov@intel.com>; dpdk-dev <dev@dpdk.org>
> *Subject:* RE: [dpdk-dev] eal: DPDK: 18.11.6 version rte_eal_init() 
> function cleans the runtime directory in 5.4.35 kernel
> 
> Hi Anatoly - Thanks for helping on this.
> 
> I am not aware, where the primary process re-creates the files. Can you 
> please point me to that? As per my code browsing and understanding, I 
> can see, fbarray_memzone file gets created in 
> rte_eal_memzone_init()->rte_fbarray_init() and it stays there till 
> eal_clean_runtime_dir() gets called towards end of rte_eal_init(). This 
> does not get deleted in 4.19 kernel, but in 5.4, it does.
> 
> /I'm not sure i understand. Primary process is supposed to clear the
> files. It will then recreate them. Are you suggesting that it's clearing
> them *after* it has created them?/
> 
> /
> /Going by my observation, the file highlighted below gets deleted by the 
> time rte_eal_init() is over.
> 
> srwxr-xr-x 1 root root      0 Oct 15 11:24 mp_socket
> 
> -rw------- 1 root root  12432 Oct 15 11:24 hugepage_info
> 
> -rw------- 1 root root 188416 Oct 15 11:24 fbarray_memzone
> 
> -rw------- 1 root root 397312 Oct 15 11:24 fbarray_memseg-2048k-0-1
> 
> -rw------- 1 root root 397312 Oct 15 11:24 fbarray_memseg-2048k-0-0
> 
> -rw------- 1 root root 397312 Oct 15 11:24 fbarray_memseg-2048k-0-3
> 
> -rw------- 1 root root 397312 Oct 15 11:24 fbarray_memseg-2048k-0-2
> 
> -rw------- 1 root root  16529 Oct 15 11:24 config
> 
> Please reach out to me for further clarification.
> 
> Regards
> 
> Amiya

Hi,

Sorry, yes, you're right (it's been a while since i looked at the code), 
it removes unused stuff at the end of init. There's even a comment 
explaining why that's done :D

It sounds like closing the file descriptor also drops the lock. This 
locking business is a huge pain because we have to support old kernels 
which don't have the only sane file locking implementation that Linux has.

While i wouldn't go as far as to say "this is a kernel regression" as 
most likely it's me who's at fault here, but this definitely shouldn't 
happen. Unfortunately, i won't be online for the next two weeks, but 
i'll definitely look into this after i'm back, so thanks for your report.

-- 
Thanks,
Anatoly