PHP-FPM processes hang in UFS-state

[Konstantin Belousov]

On Sat, Oct 24, 2020 at 03:27:14PM +0300, Christos Chatzaras wrote:
> This issue happened in 3 different servers the last months.
> 
> Some PHP-FPM processes hang in UFS-state.
> 
> The websites that cause the hang are all Prestashop and it's related to their var/cache files (I believe it happens when they clear the cache and the files are regenerated).
> 
> 
> This is a php-fpm process that hang:
> 
> procstat -kk 73548
> 
>   PID    TID COMM                TDNAME              KSTACK
> 73548 100630 php-fpm             -                   mi_switch+0xe2 sleepq_wait+0x2c sleeplk+0x185 lockmgr_xlock_hard+0x1f5 __lockmgr_args+0x2bf ffs_lock+0xa5 VOP_LOCK1_APV+0x7c _vn_lock+0x44 vget+0x4a vfs_hash_get+0xb0 ffs_vgetf+0x3f softdep_sync_buf+0xbee ffs_syncvnode+0x26f ffs_truncate+0x71b ufs_direnter+0x5f8 ufs_makeinode+0x5fb ufs_create+0x34 VOP_CREATE_APV+0x76 
> 
> 
> procstat -kk -a :
> 
> https://www.coderz.gr/ufs/procstat.txt <https://pastebin.com/raw/Wd8s3AT1>
> 
> 
> mount | grep home :
> 
> https://www.coderz.gr/ufs/mount.txt <https://www.coderz.gr/ufs/mount.txt>
> 
> 
> dumpfs /dev/mirror/gm0p7 :
> 
> https://www.coderz.gr/ufs/dumpfs.txt <https://www.coderz.gr/ufs/dumpfs.txt>
> 
> 
> I have to force reboot the server as /home is not possible to clean unmount. Then I run fsck which fixes some issues because of the unclean reboot. Then I run fsck again that shows no errors. Then I mount /home and first rename the cache folders and finally delete var/cache and allow it to regenerate prestashop files. But the same issue happens again after few days.
> 
> 
> Any idea how to troubleshoot it?

Do you have quotas enabled ?  Does the problem disappear with quotas
turned off ?

Regardless of the quotas question, If the issue is reproducable, first
upgrade to 12.2 at least. Then follow instructions at
https://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html