Re: any way to recover from I/O hang?

Hi,

> On 26 Nov 2025, at 14:16, Anthony Pankov <anthony.pankov@yahoo.com> wrote:
> 
> 
> Recently I'm again facing a situation where some UFS (?) error on one partition forced me to reboot whole server and interrupt people's work.
> As I understand the brief is:
> 
> Reason: A process in state 'D' (uninterruptible wait/sleep) is blocked on an I/O operation (e.g., waiting for a network file share, a disk operation, or a device that is no longer responding) at the kernel level. The process is not awaken to handle signals until the condition it is waiting for is resolved.
> Solution: You cannot kill a 'D' state process with any signal, including SIGKILL (kill -9). The condition must be resolved (e.g., fixing the network connection, waiting for the I/O to time out, or potentially unmounting the filesystem with umount -f if it's a mounted network share). In some rare cases involving buggy kernel code or hardware failure, a reboot may be the only option.
> 
> In my case there was a jailed samba which share one ufs-formatted partition. The samba processes hangs one by one and sharing has stopped it work.
> There was no message in log. Geom reported no errors. Disk's has no error. It seems that there was some introduced inconsistency in UFS.
> My thoughts was to stop/kill samba, remove samba's jail, unmount partition and do fsck.
> 
> But 'jail -r' exit with something 'rc.shutdown exited ... 9' and left jail running. pskill -KILL for samba processes say nothing and do nothing.
> 'umount -f' say 'Device is busy'. Various utilities such as 'df' hangs. So I forced to shutdown the server which has other important and workable service to resolve the situation.
> 
> I wander is there any way to treat such a cases? May be 'umount -f' can have more power...

FWIW I have found in the past that SIGBUS will sometimes unstick a process that SIGKILL won’t shift.

> P.S. Previous situation was when I do simple (as I think) experiments with ggated and have forced to reboot server when 'mount' hung.
> 
> -- 
> Best regards,
> Anthony Pankov                         mailto:anthony.pankov@yahoo.com
> 
> 

--
Bob Bishop
rb@gid.co.uk