Process stuck in "vnread"

Maxim Sobolev sobomax at sippysoft.com
Mon Mar 28 14:32:12 UTC 2016


OK, that happened again. Now it's 10.3-RC3, funny enough, it's the same
"cp" command. Any ideas about what can be wrong here? The box is still up,
so if you need me to do something specific inside kgdb please let me know.
Thanks!

$ uname -a
FreeBSD abc01.sippysoft.com 10.3-RC3 FreeBSD 10.3-RC3 #0 bedc749(master):
Wed Mar 23 14:39:07 PDT 2016
sobomax at abc01.sippysoft.com:/usr/obj/usr/home/sobomax/projects/freebsd103/sys/ABC01
 amd64


$ ps -xaHl -O lwp
 UID   PID  PPID CPU  PRI NI     VSZ     RSS MWCHAN   STAT TT        TIME
COMMAND            PID    LWP TT  STAT       TIME COMMAND
   0 39143 38949   0   52  0   12368    1064 vnread   DL+   2     0:00.00
cp /usr/local/sh 39143 101176  2  DL+     0:00.00 cp
/usr/local/share/automake-1.15/compile ./compile


(kgdb) thread 473
[Switching to thread 473 (Thread 101176)]#0  sched_switch
(td=0xfffff803320b84b0, newtd=<value optimized out>, flags=<value optimized
out>)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/sched_ule.c:1945
1945                    cpuid = PCPU_GET(cpuid);
(kgdb) bt
#0  sched_switch (td=0xfffff803320b84b0, newtd=<value optimized out>,
flags=<value optimized out>)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/sched_ule.c:1945
#1  0xffffffff809364d1 in mi_switch (flags=260, newtd=0x0) at
/usr/home/sobomax/projects/freebsd103/sys/kern/kern_synch.c:491
#2  0xffffffff809761ca in sleepq_wait (wchan=0x0, pri=0) at
/usr/home/sobomax/projects/freebsd103/sys/kern/subr_sleepqueue.c:618
#3  0xffffffff80935ef7 in _sleep (ident=<value optimized out>, lock=<value
optimized out>, priority=<value optimized out>, wmesg=<value optimized out>,
    sbt=<value optimized out>, pr=<value optimized out>, flags=<value
optimized out>) at
/usr/home/sobomax/projects/freebsd103/sys/kern/kern_synch.c:255
#4  0xffffffff809b7c6e in bwait (bp=0xfffffe03e1012048, pri=<value
optimized out>, wchan=0xffffffff81069471 "vnread")
    at /usr/home/sobomax/projects/freebsd103/sys/kern/vfs_bio.c:4431
#5  0xffffffff80b56663 in vnode_pager_generic_getpages
(vp=0xfffff802b7e73588, m=0xfffffe0468c4ebe0, bytecount=<value optimized
out>,
    reqpage=<value optimized out>) at
/usr/home/sobomax/projects/freebsd103/sys/vm/vnode_pager.c:907
#6  0xffffffff80dd7fa7 in VOP_GETPAGES_APV (vop=<value optimized out>,
a=<value optimized out>) at vnode_if.c:2795
#7  0xffffffff80b54a0a in vnode_pager_getpages (object=<value optimized
out>, m=0xfffffe0468c4ebe0, count=<value optimized out>, reqpage=0)
    at vnode_if.h:1154
#8  0xffffffff80b354a1 in vm_fault_hold (map=0xfffff800294c98c0,
vaddr=34366300160, fault_type=<value optimized out>, fault_flags=0,
m_hold=0x0)
    at vm_pager.h:127
#9  0xffffffff80b34c07 in vm_fault (map=0xfffff800294c98c0, vaddr=<value
optimized out>, fault_type=1 '\001', fault_flags=0)
    at /usr/home/sobomax/projects/freebsd103/sys/vm/vm_fault.c:273
#10 0xffffffff80cbaef5 in trap_pfault (frame=0xfffffe0468c4f040,
usermode=0) at
/usr/home/sobomax/projects/freebsd103/sys/amd64/amd64/trap.c:747
#11 0xffffffff80cba65d in trap (frame=0xfffffe0468c4f040) at
/usr/home/sobomax/projects/freebsd103/sys/amd64/amd64/trap.c:447
#12 0xffffffff80ca0592 in calltrap () at
/usr/home/sobomax/projects/freebsd103/sys/amd64/amd64/exception.S:236
#13 0xffffffff80cb8b71 in copyin () at
/usr/home/sobomax/projects/freebsd103/sys/amd64/amd64/support.S:311
#14 0xffffffff8097d70f in uiomove_faultflag (cp=<value optimized out>,
n=<value optimized out>, uio=0xfffffe0468c4f960, nofault=<value optimized
out>)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/subr_uio.c:253
---Type <return> to continue, or q <return> to quit---
#15 0xffffffff819f799c in dmu_write_uio_dnode () from /boot/kernel/zfs.ko
#16 0xffffffff819f78b2 in dmu_write_uio_dbuf () from /boot/kernel/zfs.ko
#17 0xffffffff81a91a07 in zfs_freebsd_write () from /boot/kernel/zfs.ko
#18 0xffffffff80dd6219 in VOP_WRITE_APV (vop=<value optimized out>,
a=<value optimized out>) at vnode_if.c:999
#19 0xffffffff808730b2 in null_bypass (ap=0xfffffe0468c4f7d0) at
/usr/home/sobomax/projects/freebsd103/sys/fs/nullfs/null_vnops.c:280
#20 0xffffffff80dd621f in VOP_WRITE_APV (vop=<value optimized out>,
a=<value optimized out>) at vnode_if.c:1001
#21 0xffffffff809dea28 in vn_write (fp=0xfffff8004bc0ddc0,
uio=0xfffffe0468c4f960, active_cred=0x1ca5, flags=916,
td=0xfffffe00006a60d0)
    at vnode_if.h:413
#22 0xffffffff809dad6b in vn_io_fault (fp=0xfffff8004bc0ddc0,
uio=0xfffffe0468c4f960, active_cred=0x1ca5, flags=0, td=0xfffffe00006a60d0)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/vfs_vnops.c:1225
#23 0xffffffff80981937 in dofilewrite (td=0xfffff803320b84b0, fd=4,
fp=0xfffff8004bc0ddc0, auio=0xfffffe0468c4f960, offset=<value optimized
out>,
    flags=0) at file.h:305
#24 0xffffffff80981668 in kern_writev (td=0xfffff803320b84b0, fd=4,
auio=0xfffffe0468c4f960)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/sys_generic.c:481
#25 0xffffffff809815f3 in sys_write (td=<value optimized out>, uap=<value
optimized out>)
    at /usr/home/sobomax/projects/freebsd103/sys/kern/sys_generic.c:396
#26 0xffffffff80cbb559 in amd64_syscall (td=0xfffff803320b84b0, traced=0)
at subr_syscall.c:141
#27 0xffffffff80ca087b in Xfast_syscall () at
/usr/home/sobomax/projects/freebsd103/sys/amd64/amd64/exception.S:396
#28 0x0000000800968f5a in ?? ()


On Wed, Mar 2, 2016 at 1:12 AM, Maxim Sobolev <sobomax at freebsd.org> wrote:

> Hi, I've encountered cp(1) process stuck in the vnread state on one of my
> build machines that got recently upgraded to 10.3.
>
>    0 79596     1   0  20  0   17092    1396 wait     I     1       0:00.00
> /bin/sh /usr/local/bin/autoreconf -f -i
>    0 79602 79596   0  52  0   41488    9036 wait     I     1       0:00.07
> /usr/local/bin/perl -w /usr/local/bin/autoreconf-2.69 -f -i
>    0 79639 79602   0  72  0       0       0 -        Z     1       0:00.27
> <defunct>
>    0 79762 79602   0  20  0   17092    1396 wait     I     1       0:00.00
> /bin/sh /usr/local/bin/automake --add-missing --copy --force-missing
>    0 79768 79762   0  52  0   49736   13936 wait     I     1       0:00.11
> /usr/local/bin/perl -w /usr/local/bin/automake-1.15 --add-missing --copy
> --force-missing
>    0 79962 79768   0  20  0   12368    1024 vnread   DL    1       0:00.00
> cp /usr/local/share/automake-1.15/compile ./compile
>
> I am not sure if it's related to that OS version upgrade, but I have not
> seen any such issues on the same machine in 2-3 years running essentially
> the same build process with version 9.x, 10.0, 10.1 and 10.2.
>
> $ uname -a
> FreeBSD van01.sippysoft.com 10.3-PRERELEASE FreeBSD 10.3-PRERELEASE #1
> 80de3e2(master)-dirty: Tue Feb  2 12:19:57 PST 2016
> sobomax at abc.sippysoft.com:/usr/obj/usr/home/sobomax/projects/freebsd103/sys/ABC
>  amd64
>
> The kernel stack trace is:
>
> (kgdb) thread 360
> [Switching to thread 360 (Thread 100515)]#0  0xffffffff8095244e in
> sched_switch ()
> (kgdb) bt
> #0  0xffffffff8095244e in sched_switch ()
> #1  0xffffffff809313b1 in mi_switch ()
> #2  0xffffffff8097089a in sleepq_wait ()
> #3  0xffffffff80930dd7 in _sleep ()
> #4  0xffffffff809b230e in bwait ()
> #5  0xffffffff80b511f3 in vnode_pager_generic_getpages ()
> #6  0xffffffff80dd1607 in VOP_GETPAGES_APV ()
> #7  0xffffffff80b4f59a in vnode_pager_getpages ()
> #8  0xffffffff80b30031 in vm_fault_hold ()
> #9  0xffffffff80b2f797 in vm_fault ()
> #10 0xffffffff80cb5a75 in trap_pfault ()
> #11 0xffffffff80cb51dd in trap ()
> #12 0xffffffff80c9b122 in calltrap ()
> #13 0xffffffff80cb36f1 in copyin ()
> #14 0xffffffff80977ddf in uiomove_faultflag ()
>
> The FS stack configuration is somewhat unique, so I am not sure if I am
> hitting some rare race condition or lock ordering issues specific to that.
> It's basically ZFS (ZRAID) on top of pair or SATA SSDs with big file on
> that FS attached via md(4) and UFS2 on that md(4). The build itself runs in
> chroot with that UFS2 fs as its primary root.
>
> Just maybe additional bit of info, attempting to list the directory with
> that UFS image also got my bash process stuck in "zfs" state, backtrace
> from that is:
>
> (kgdb) thread 353
> [Switching to thread 353 (Thread 100508)]#0  0xffffffff8095244e in
> sched_switch ()
> (kgdb) bt
> #0  0xffffffff8095244e in sched_switch ()
> #1  0xffffffff809313b1 in mi_switch ()
> #2  0xffffffff8097089a in sleepq_wait ()
> #3  0xffffffff809069ad in sleeplk ()
> #4  0xffffffff809060e0 in __lockmgr_args ()
> #5  0xffffffff809b8b7c in vop_stdlock ()
> #6  0xffffffff80dd0a3b in VOP_LOCK1_APV ()
> #7  0xffffffff809d6d23 in _vn_lock ()
> #8  0xffffffff81a8c9cd in ?? ()
> #9  0x0000000000000000 in ?? ()
>
>
>


-- 
Maksym Sobolyev
Sippy Software, Inc.
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