Processes getting stuck in "fstchg" with NetBSD-10.99.12/amd64
Brian Buhrow <[email protected]>
| Newsgroups | gmane.os.netbsd.devel.kernel |
|---|---|
| Message-ID | <[email protected]> |
hello. I have a number of machines running NetBSD-10.99.12/amd64 running on real hardware and running as VM machines, mostly xen, but also as guests on KVM. Out of approximately 25 different instances, I have one Xen machine where processes "hang". The machine may run for a week before this happens, or it may run for months. To try and figure out what is going wrong, I installed a kernel with ddb in it and when the problem manifested itself, I discovered processes and threads that look like: PID LID S CPU FLAGS STRUCT LWP * NAME WAIT 28144 28144 3 0 0 ffff9dde28395400 sshd fstchg 2416 2416 3 0 0 ffff9dde28395000 sshd fstchg 1481 1481 3 0 0 ffff9ddcf99dfc00 sshd fstchg 6400 6400 3 1 0 ffff9ddcf99df800 cron fstchg 28098 28098 3 0 0 ffff9ddcf99df400 cron fstchg 5484 5484 3 1 0 ffff9ddcf99df000 cron fstchg 1394 1394 3 0 0 ffff9ddd25e8fc00 cron fstchg 26447 26447 3 0 0 ffff9ddd25e8f800 cron fstchg . . . 0 123 3 0 200 ffff9dddfd0bac00 ioflush fstchg The system is: NetBSD lothlorien.nfbcal.org 10.99.12 NetBSD 10.99.12 (MIRKWOOD_PVH_DDB) #0: Mon Apr 7 05:50:18 PDT 2025 [email protected]:/usr/src/sys/arch/amd64/compile/MIRKWOOD_PVH_DDB amd64 In looking at the code, I see these processes are waiting to do something with the filesystem or filesystems. There are a number of mounted partitions, all ffs, plus a ptyfs filesystem running in compatibility mode, i.e. /dev/ttypx, rather than /dev/pts/*, which means it doesn't show up as a filesystem at all. My questions are as follows: 1. How do I find which one of these is the blocking process? 2. Has anyone else seen this behavior? As I say, only one of my many machines exhibits this behavior, and it is a Xen guest on which other VM's running the exact same code, are working fine for months at a time. Suggestions welcome. -thanks -Brian