It appears that kernel 2.6.17-rc5 under amd64 may be hanging I/O
processes spontaneously at random.
Our setup here uses drbd (ver. 0.7.19), which is a network RAID
kernel module, and initially I was fscking (ext3) filesystems, which
are on drbd devices, and the fsck just stopped spontaneously on the
two of them.
Today, I tried copying a directory on the command line with cp -a on
this computer (on a drbd-managed device) and then in mid-copy I tried
to abort the process with control-C. It did not abort. I tried
killing it with kill and then with kill -9. It turns out that the
process had died, but is still left in ps.
Anyway, I tried bringing down the peer and bringing it back up and it stalled.
I also had an emerge sync (i.e., the Gentoo update mechanism) going
and it too got stuck, but it doesn't, or at least shouldn't affect
drbd disks, implying this is not a drbd bug, but a kernel bug.
* what are the numbers in /proc/drbd
This is how it appears long after the copy hang and I stopped and
just restarted drbd on the peer. The output from then hanging
computer:
version: 0.7.19 (api:78/proto:74)
SVN Revision: 2212 build by root@thewarehouse1, 2006-05-28 17:54:59
0: cs:SyncSource st:Primary/Secondary ld:Consistent
ns:844864 nr:0 dw:325684 dr:940453 al:200 bm:123 lo:0 pe:0 ua:13 ap:0
[===================>] sync'ed:100.0% (52/52)K
stalled
1: cs:SyncSource st:Primary/Secondary ld:Consistent
ns:41686716 nr:0 dw:41166664 dr:57457996 al:76392 bm:94 lo:0
pe:0 ua:0 ap:0
[===================>] sync'ed:100.0% (120/120)K
stalled
2: cs:SyncSource st:Primary/Secondary ld:Consistent
ns:45970636 nr:0 dw:45451468 dr:27302312 al:45571 bm:63 lo:0
pe:0 ua:0 ap:0
[===================>] sync'ed:100.0% (1020/1020)K
stalled
3: cs:PausedSyncS st:Primary/Secondary ld:Consistent
ns:284957716 nr:0 dw:284450048 dr:251121904 al:266659 bm:759 lo:0
pe:0 ua:0 ap:0
4: cs:WFReportParams st:Primary/Unknown ld:Consistent
ns:92534448 nr:0 dw:133197016 dr:64860944 al:157353 bm:21176
lo:19 pe:0 ua:0 ap:0
5: cs:WFReportParams st:Primary/Unknown ld:Consistent
ns:64605420 nr:0 dw:64085232 dr:54424576 al:132822 bm:121 lo:6
pe:0 ua:0 ap:0
6: cs:Connected st:Primary/Secondary ld:Consistent
ns:88661276 nr:0 dw:88141084 dr:43618112 al:123587 bm:122 lo:0
pe:0 ua:0 ap:0
7: cs:PausedSyncS st:Primary/Secondary ld:Consistent
ns:79213408 nr:0 dw:78693368 dr:42392908 al:184445 bm:128 lo:0
pe:0 ua:0 ap:0
8: cs:WFReportParams st:Primary/Unknown ld:Consistent
ns:114288948 nr:0 dw:114035536 dr:113012216 al:80028 bm:2102 lo:2
pe:0 ua:0 ap:0
* get the wchan of the stuck processes
via top, or ps -eo pid,wchan:40,comm, or cat /proc/<pid>/wchan
(not only the fsck, but everything that may be
related, so fs-related kernel threads, vm-related
kernel threads, drbd-related kernel-threads).
PID WCHAN COMMAND STAT
1 select init Ss
2 migration_thread migration/0 S
3 ksoftirqd ksoftirqd/0 SN
4 watchdog watchdog/0 S
5 migration_thread migration/1 S
6 ksoftirqd ksoftirqd/1 SN
7 watchdog watchdog/1 S
8 worker_thread events/0 S<
9 worker_thread events/1 S<
10 worker_thread khelper S<
11 worker_thread kthread S<
16 worker_thread kblockd/0 S<
17 worker_thread kblockd/1 S<
18 serio_thread kseriod S<
108 drbd_al_begin_io kswapd0 D
109 drbd_al_begin_io kswapd1 D
110 worker_thread aio/0 S<
111 worker_thread aio/1 S<
746 scsi_error_handler scsi_eh_0 S<
750 worker_thread ata/0 S<
751 worker_thread ata/1 S<
774 worker_thread kpsmoused S<
1380 worker_thread kmirrord S<
1918 scsi_error_handler scsi_eh_1 S<
2136 kjournald kjournald S<
2801 select udevd S<s
3842 kjournald kjournald S<
3844 kjournald kjournald S<
5638 sys_poll metalog Ss
5639 syslog metalog S
6597 select sshd Ss
6767 sk_wait_data drbd0_receiver S
6769 sk_wait_data drbd1_receiver S
6771 sk_wait_data drbd7_receiver S
6773 sk_wait_data drbd2_receiver S
6775 sk_wait_data drbd3_receiver S
6777 drbd_determin_dev_size drbd8_receiver D
6779 drbd_determin_dev_size drbd4_receiver D
6781 drbd_determin_dev_size drbd5_receiver D
6783 sk_wait_data drbd6_receiver S
7013 sys_poll heartbeat SLs
7035 pipe_wait heartbeat SL
7036 sys_poll heartbeat SL
7037 skb_recv_datagram heartbeat SL
7184 wait mon S
7327 skb_recv_datagram portsentry Ss
7329 skb_recv_datagram portsentry Ss
7444 select master Ss
7459 select qmgr S
7589 hrtimer_nanosleep cron Ss
7717 read_chan agetty Ss+
7718 read_chan agetty Ss+
7719 read_chan agetty Ss+
7720 read_chan agetty Ss+
7721 read_chan agetty Ss+
7722 read_chan agetty Ss+
8923 kjournald kjournald S<
8971 kjournald kjournald S<
9019 kjournald kjournald S<
9067 kjournald kjournald S<
9115 drbd_al_begin_io kjournald D<
9163 kjournald kjournald S<
9211 kjournald kjournald S<
9259 kjournald kjournald S<
9307 drbd_al_begin_io kjournald D<
9438 select atalkd S
9544 select smbd Ss
9548 pause smbd S
9554 select nmbd Ss
9688 select mysqld Ssl
9901 select cnid_metad S
9910 select afpd S
11332 compat_sys_nanosleep retroclient Ss
11333 sys_poll retroclient S
11335 compat_sys_nanosleep retroclient S
11336 inet_csk_accept retroclient S
11337 skb_recv_datagram retroclient S
11344 inet_csk_accept retroclient S
11345 skb_recv_datagram retroclient S
11352 inet_csk_accept retroclient S
11353 skb_recv_datagram retroclient S
11360 inet_csk_accept retroclient S
11365 compat_sys_nanosleep retroclient S
11908 select cnid_dbd S
8270 select smbd S
10289 drbd_al_begin_io smbd D
31891 select smbd S
29010 drbd_al_begin_io smbd D
24530 select smbd S
32250 pdflush pdflush S
19751 drbd_al_begin_io pdflush D
3856 sk_wait_data afpd S
8543 select smbd S
11364 sk_wait_data afpd S
27917 sk_wait_data afpd S
27918 select cnid_dbd S
22538 select smbd S
12830 select smbd S
17962 select smbd S
23331 select smbd S
28361 select smbd S
28411 wait bash S
3404 select smbd S
13660 select smbd S
23339 sk_wait_data afpd S
27168 kjournald kjournald S<
25449 select smbd S
28328 select smbd S
32490 select apache2 Ss
24761 skb_recv_datagram apache2 S
24764 inet_csk_accept apache2 S
24765 inet_csk_accept apache2 S
24766 inet_csk_accept apache2 S
24767 inet_csk_accept apache2 S
24768 inet_csk_accept apache2 S
2091 select smbd S
10197 select smbd S
10832 select smbd S
15513 select smbd S
19215 select smbd S
19585 select smbd S
19761 drbd_al_begin_io smbd D
21619 inet_csk_accept apache2 S
21620 inet_csk_accept apache2 S
30680 select smbd S
31724 select smbd S
32105 sk_wait_data afpd S
8343 select smbd S
17100 sk_wait_data afpd S
14374 compat_sys_nanosleep retroclient S
14376 get_write_access retropds.23 D
14397 pipe_wait retroclient S
27942 pipe_wait cron S
27943 wait bash Ss
27944 wait run-crons S
27973 wait hotbackup_daily S
27976 wait hotbackup_daily S
28053 pipe_wait sendmail S
28056 unix_stream_recvmsg postdrop S
28058 sync_buffer mv D
28509 get_write_access find D
28512 pipe_wait sort S
28514 pipe_wait sed S
12803 wait slocate S
12804 vfs_readdir updatedb DN
28845 drbd_al_begin_io smbd D
2145 drbd_al_begin_io smbd D
2885 select smbd S
3571 select smbd S
5313 select smbd S
5417 drbd_al_begin_io smbd D
5444 drbd_al_begin_io mon D
5468 drbd_al_begin_io smbd D
6218 wait bash S
6237 drbd_al_begin_io cp D
6332 wait bash S
6340 vfs_unlink rm D
6390 select smbd S
6499 vfs_readdir ls D
6595 sk_wait_data afpd S
6947 log_wait_commit cnid_dbd D
7084 sk_wait_data afpd S
7136 drbd_al_begin_io smbd D
7149 select smbd S
7213 drbd_al_begin_io afpd D
7754 drbd_al_begin_io smbd D
7757 drbd_al_begin_io afpd D
7758 drbd_al_begin_io smbd D
7764 select smbd S
7771 pipe_wait cron S
7772 wait bash Ss
7773 drbd_al_begin_io run-crons D
7778 drbd_al_begin_io afpd D
8002 select smbd S
8088 select smbd S
8220 drbd_al_begin_io afpd D
8222 log_wait_for_space cnid_dbd D
8482 drbd_al_begin_io emerge D
9451 select smbd S
9575 drbd_al_begin_io afpd D
9613 wait mail.alert S
9614 unix_stream_recvmsg sendmail S
9616 drbd_al_begin_io postdrop D
9633 sk_wait_data afpd S
9697 select pickup S
9918 drbd_al_begin_io emerge D
9924 drbd_al_begin_io sshd D
9936 unix_stream_recvmsg sshd Ss
9941 select sshd S
9942 wait bash Ss
9951 unix_stream_recvmsg sshd Ss
9956 select sshd S
9957 wait bash Ss
9962 read_chan bash S+
10126 drbd_thread_setup drbd6_worker S
10136 select smbd S
10142 sk_wait_data drbd6_asender S
10143 sk_wait_data drbd0_asender S
10144 sk_wait_data drbd2_asender S
10145 sk_wait_data drbd1_asender S
10146 sk_wait_data drbd3_asender S
10147 sk_wait_data drbd7_asender S
10163 - ps R+
* get a backtrace of the stuck processess
e.g. echo t > /proc/sysrq-trigger
(again, everything that may be related)
note that these are not necessarily reliable,
but may be helpful to understand whats going on.
The above and remaining portions of this post are available entirely
online at
http://www.kennedy.aecom.yu.edu/misc/kernel_2.6.17-rc5_drbd_hanging_io.html
--
Maurice Volaski, [email protected]
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University
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