All processes go tstile

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

Hello

Another dump/snapshot problem that seems to have surfaced with
NetBSD 8.0: I run a dump with snapshot, and after a while, 
all processes get stuck in tstile.

This happens with GENERIC kernel, though I added LOCKDEBUG to 
investigate.

Processes backtrace show namei/VOP_LOCK/rw_enter and  following
the locks owner, it seems everyone is  ultimately waiting for ioflush, i
which itself is stuck with this backtrace:

sleepq_block
cv_wait
fstrans_start
VOP_BWRITE
getnewbuf
getblk
bio_doread
bread
ffs_update.part.3
ffs_sync
VFS_SYNC
sched_sync

If I understand correctly, that means a n I/O that never completed, right?

Anyone has something to test here before I downgrade this machine to 7.1.2?

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost