Re: NFSv4 hangs on 13.3

On Fri, May 31, 2024 at 12:39 PM J David <j.david.lists@gmail.com> wrote:
>
> In an attempt to narrow down the problems we have with NFS v4.2, we've
> set up a FreeBSD 13.3 server that mirrors some read-only data from our
> Linux NFS servers.
>
> We are still observing occasional hangs on the FreeBSD 13.3 client machines.
>
> When these hangs occur, anything that touches the mountpoint
> (including "umount -N") hangs indefinitely. There is nothing in dmesg.
>
> The only even slightly informative data I could gather is an "ls
> /mount/point" kstack:
>
> $ sudo procstat -kk 94676
>   PID    TID COMM                TDNAME              KSTACK
> 94676 976876 ls                  -                   mi_switch+0xbf
> sleeplk+0xea lockmgr_slock_hard+0x3a5 nfs_lock+0x29 vop_sigdefer+0x2a
> _vn_lock+0x47 vfs_cache_root+0x9d vfs_root_sigdefer+0x35 lookup+0x88a
> namei+0x24a kern_statat+0xf8 sys_fstatat+0x27 amd64_syscall+0x110
> fast_syscall_common+0xf8
>
> During this time, the NFS server continues serving other clients, and
> the affected client can access other NFS servers without hanging.
>
> The "nfsstat -m" for this mountpoint looks like this:
>
> nfsv4,minorversion=2,oneopenown,tcp,resvport,nconnect=1,hard,cto,nolockd,sec=sys,acdirmin=3,acdirmax=60,acregmin=5,acregmax=60,nametimeo=60,negnametimeo=60,rsize=65536,wsize=65536,readdirsize=65536,readahead=1,wcommitsize=16777216,timeout=120,retrans=2147483647
>
> with these mount flags in /etc/fstab:
>
> ro,nfsv4,minorversion=2,tcp,nosuid,noatime,nolockd,oneopenown
>
> Is there anything more we can do to help identify this issue?
Collect the output of:
# ps axHl
and
# procstat -kk -a

What you show above is just a thread waiting for a lock on an NFS vnode.
What we need to figure out is what thread is holding the lock on that vnode
while waiting for something else.

rick

>
> Thanks for any advice!
>