What does procstat -k -k report?
----- Original Message -----
From: "Mark Martinec" <Mark.Martinec+freebsd at ijs.si>
To: <freebsd-stable at freebsd.org>
Sent: Friday, October 10, 2014 12:59 AM
Subject: zfs pool import hangs on [tx->tx_sync_done_cv]
> In short, after upgrading to 10.1-BETA3 or -RC1 I ended up with several
> zfs pools that can no longer be imported. The zpool import command
> (with no arguments) does show all available pools, but trying to
> import one just hangs and the command cannot be aborted, although
> the rest of the system is still alive and fine:
>
> # zpool import -f <mypool>
>
> Typing ^T just shows an idle process, waiting on [tx->tx_sync_done_cv]:
>
> load: 0.20 cmd: zpool 939 [tx->tx_sync_done_cv] 5723.65r 0.01u 0.02s 0%
> 8220k
> load: 0.16 cmd: zpool 939 [tx->tx_sync_done_cv] 5735.73r 0.01u 0.02s 0%
> 8220k
> load: 0.14 cmd: zpool 939 [tx->tx_sync_done_cv] 5741.83r 0.01u 0.02s 0%
> 8220k
> load: 0.13 cmd: zpool 939 [tx->tx_sync_done_cv] 5749.16r 0.01u 0.02s 0%
> 8220k
>
> ps shows (on a system re-booted to a LiveCD running FreeBSD-10.1-RC1):
>
> PID TID COMM TDNAME CPU PRI STATE WCHAN
> 939 100632 zpool - 5 122 sleep tx->tx_s
> UID PID PPID CPU PRI NI VSZ RSS MWCHAN STAT TT TIME COMMAND
> 0 939 801 0 22 0 107732 8236 tx->tx_s D+ v0 0:00.04
> zpool import -f -o cachefile=/tmp/zpool.cache -R /tmp/sys0boot sys0boot
>
> NWCHAN
> fffff8007b0f2a20
>
> # procstat -kk 939
>
> PID TID COMM TDNAME KSTACK
> 939 100632 zpool - mi_switch+0xe1
> sleepq_wait+0x3a _cv_wait+0x16d txg_wait_synced+0x85 spa_load+0x1cd1
> spa_load_best+0x6f spa_import+0x1ff zfs_ioc_pool_import+0x137
> zfsdev_ioctl+0x6f0 devfs_ioctl_f+0x114 kern_ioctl+0x255 sys_ioctl+0x13c
> amd64_syscall+0x351 Xfast_syscall+0xfb
>
>
> Background story: the system where this happened was being kept
> to a fairly recent 10-STABLE. The last upgrade was very close to
> a BETA3 release. There are a couple of zfs pools there, one on a
> mirrored pair of SSDs mostly holding the OS, one with a mirrored
> pair of large spindles, and three more small ones (4 GiB each),
> mostly for boot redundancy or testing - these small ones are on
> old smallish disks. These disks are different, and attached to
> different SATA controllers (LSI and onboard Intel). Pools were
> mostly kept up-to-date to the most recent zpool features set
> through their lifetime (some starting their life with 9.0, some
> with 10.0).
>
> About two weeks ago after a reboot to a 10-STABLE of the day
> the small pools became unavailable, but the regular two large
> pools were still normal. At first I wasn't giving much attention
> to that, as these pools were on oldish disks and nonessential
> for normal operation, blaming a potentially crappy hw.
>
> Today I needed to do a reboot (for unrelated reason), and the
> machine was no longer able to mount the boot pool.
> The first instinct was - disks are malfunctioning - but ...
>
> Booting it to a FreeBSD-10.1-RC1 LiveCD was successful.
> smartmon disk test shows no problems. dd is able to read whole
> partititions of each problematic pool. And most importantly,
> running a 'zdb -e -cc' on each (non-imported) pool was churning
> normally and steadily, producing a stats report at the end
> and reported no errors.
>
> As a final proof that disks are fine I sacrificed one of the broken
> 4 GiB GPT partitions with one of the problematic pools, and
> did a fresh 10.1-RC1 install on it from a distribution ISO DVD.
> The installation went fine and the system does boot and run
> fine from the newly installed OS. Trying to import one of the
> remaining old pools hangs the import command as before.
>
> As a final proof, I copied (with dd) one of the broken 4 GiB
> partitions to a file on another system (running 10.1-BETA3,
> which did not suffer from this problem), made a memory disk
> out of this file, then run zfs import on this pool - and it hangs
> there too! So hardware was not a problem - either these partitions
> are truly broken (even though zdb -cc says they are fine),
> or the new OS is somehow no longer able to import them.
>
> Please advise.
>
> I have a copy of the 4 GiB partition on a 400 MB compressed
> file available, if somebody would be willing to play with it.
>
> Also have a ktrace of the 'zpool import' command. It's last
> actions before it hangs are:
>
> 939 zpool RET madvise 0
> 939 zpool CALL madvise(0x80604e000,0x1000,MADV_FREE)
> 939 zpool RET madvise 0
> 939 zpool CALL close(0x6)
> 939 zpool RET close 0
> 939 zpool CALL ioctl(0x3,0xc0185a05,0x7fffffffbf00)
> 939 zpool RET ioctl -1 errno 2 No such file or directory
> 939 zpool CALL madvise(0x802c71000,0x10000,MADV_FREE)
> 939 zpool RET madvise 0
> 939 zpool CALL madvise(0x802ca5000,0x1000,MADV_FREE)
> 939 zpool RET madvise 0
> 939 zpool CALL ioctl(0x3,0xc0185a06,0x7fffffffbf60)
> 939 zpool RET ioctl 0
> 939 zpool CALL ioctl(0x3,0xc0185a06,0x7fffffffbf60)
> 939 zpool RET ioctl 0
> 939 zpool CALL stat(0x802c380e0,0x7fffffffbc58)
> 939 zpool NAMI "/tmp"
> 939 zpool STRU struct stat {dev=273, ino=2, mode=041777,
> nlink=8, uid=0, gid=0, rdev=96, atime=1412866648, stime=1412871393,
> ctime=1412871393, birthtime=1412866648, size=512, blksize=32768,
> blocks=8, flags=0x0 }
> 939 zpool RET stat 0
> 939 zpool CALL ioctl(0x3,0xc0185a02,0x7fffffffbc60)
>
>
> Mark
>
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