[v5.4.28-rt19] ARM64: nfs boot issues

[Grygorii Strashko]

Hi All,

We now observe NFS boot issues with TI RT Kernel (last merged tag v5.4.28-rt19) on TI (ARM64) AM654x/J721E platforms.
It's just stack (100%) silently right after Kernel init (log1) or in the middle of the boot (log2).

I'm trying to investigate an issue and I'd like to ask if anybody else observed the same?

Few notes:
- I can not test clear rt-devel/linux-5.4.y-rt as above TI platform not fully supported there
- ARM32 platforms not affected
- Disabling CONFIG_PREEMPT_RT=n with CONFIG_PREEMPT=y makes NFS boot work again
- non RT Kernel has no issues

NFS configuration:
 rw rootfstype=nfs root=/dev/nfs rw nfsroot=192.168.0.110:/mnt/am65xx-evm,nolock,v3,tcp,rsize=4096,wsize=4096 ip=dhcp

===== Log1:
[   13.423029] 000: am65-cpsw-nuss 46000000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off
[   13.449187] 003: Sending DHCP requests .
[   13.457269] 002: ,
[   13.965284] 001:  OK
[   13.965769] 001: IP-Config: Got DHCP answer from 192.168.0.1, my address is 192.168.0.105
[   13.965788] 001: IP-Config: Complete:
[   13.965794] 001:      device=eth0, hwaddr=f4:84:4c:eb:a0:00, ipaddr=192.168.0.105, mask=255.255.255.0, gw=192.168.0.1
[   13.965804] 001:      host=192.168.0.105, domain=, nis-domain=(none)
[   13.965814] 001:      bootserver=0.0.0.0, rootserver=192.168.0.110, rootpath=
[   13.965821] 001:      nameserver0=192.168.0.1, nameserver1=0.0.0.0
[   13.999107] 001: ALSA device list:
[   13.999725] 001:   No soundcards found.
[   14.121815] 001: VFS: Mounted root (nfs filesystem) on device 0:21.
[   14.126072] 001: devtmpfs: mounted
[   14.139110] 001: Freeing unused kernel memory: 2688K
[   14.150126] 000: Run /sbin/init as init process
[  195.694278] 002: nfs: server 192.168.0.110 not responding, still trying
[  195.694314] 003: nfs: server 192.168.0.110 not responding, still trying
[  195.694875] 000: nfs: server 192.168.0.110 not responding, still trying
[  195.694921] 003: nfs: server 192.168.0.110 not responding, still trying
^^^

===== Log2:
[  OK  ] Stopped Network Time Synchronization.
         Starting Network Time Synchronization...
[  OK  ] Found device /dev/ttyS2.
[  OK  ] Started Network Service.
[FAILED] Failed to start Network Time Synchronization.
See 'systemctl status systemd-timesyncd.service' for details.
[   97.141595] 000: sysrq: This sysrq operation is disabled.
[  191.511935] 001: nfs: server 192.168.0.110 not responding, still trying
[  191.511995] 003: nfs: server 192.168.0.110 not responding, still trying
[  191.512001] 002: nfs: server 192.168.0.110 not responding, still trying
  
^^^

--
Best regards,
grygorii