On Sat, Jan 19, 2013 at 9:48 PM, Sedat Dilek [off-list ref] wrote:

On Sat, Jan 19, 2013 at 7:28 PM, Sedat Dilek [off-list ref] wrote:

quoted

Hi,

I am still stepping in the dark how track this problem down.
If you have useful (debug) help, you are welcome.

Regards,
- Sedat -

##### ANALYZING CALL-TRACES SEEN IN LINUX-NEXT-20130118 #####

##### INTRO

### MY LINUX-SYSTEM

I am running here Ubuntu/precise AMD64 in a WUBI environment.
The system was formatted with EXT4-FS.

### MY LINUX-KERNEL

My own built Linux-Next (next-20130118) kernel includes some additional patches,
especially a TTY-NEXT fix from Ilya Zykov.

See also attached kernel-config file, dmesg and lspci outputs.

### SOME USEFUL KERNEL DEBUG OPTIONS

CONFIG_PM_DEBUG=y
CONFIG_EXT4_DEBUG=y
CONFIG_JBD2_DEBUG=y


##### [A] ANALYZING LAST REBOOT

### [A.1] MESSAGES

# Messages #1: DBUS related?
nm-dispatcher.action: Could not get the system bus. Make sure the
message bus daemon is running! Message: Failed to connect to socket
/var/run/dbus/system_bus_socket: No such file or directory

# Messages #2: RCU_SCHED related?
INFO: rcu_sched detected stalls on CPUs/tasks: { 2 3} (detected by 1,
t=15004 jiffies, g=70928, c=70927, q=15)
INFO: task kworker/0:1:37 blocked for more than 120 seconds. "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.

### [A.2] ANALYZING DBUS PROBLEM

# ll /var/run/dbus/system_bus_socket*
srwxrwxrwx 1 root root 0 Jan 19 17:08 /var/run/dbus/system_bus_socket=

# ll /var/run/dbus/
insgesamt 4
drwxr-xr-x  2 messagebus messagebus  80 Jan 19 17:08 ./
drwxr-xr-x 22 root       root       800 Jan 19 17:11 ../
-rw-r--r--  1 root       root         4 Jan 19 17:08 pid
srwxrwxrwx  1 root       root         0 Jan 19 17:08 system_bus_socket=

# cat /var/run/dbus/pid
862

# ps axu | grep -v grep | grep 862
102        862  0.2  0.0  25492  2332 ?        Ss   17:08   0:01
dbus-daemon --system --fork --activation=upstart

# pidof dbus-daemon
1921 862

### [A.3] ANALYZING RCU_SCHED PROBLEM

# cat /proc/sys/kernel/hung_task_timeout_secs
120


##### [B] TESTCASE DESCRIPTION

### [B.1] TESTCASE #1: Do a "normal" suspend and resume

Select "suspend" (DE: "Bereitschaft") from system's menue within Ubuntu/unity.

### [B.2] TESTCASE #2: Run pm_test/freezer (PREREQ: CONFIG_PM_DEBUG=y)

HELP: <http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=Documentation/power/basic-pm-debugging.txt#l184>

# cat /sys/power/pm_test
[none] core processors platform devices freezer

# echo "freezer" > /sys/power/pm_test
# cat /sys/power/pm_test
none core processors platform devices [freezer]

# echo mem > /sys/power/state && sleep 1 <--- LOOP until you see a call-trace

### [B.3] TESTCASE #3: Change "hung_task_timeout_secs" before running
pm_test/freezer

# cat /proc/sys/kernel/hung_task_timeout_secs
120

# echo 0 > /proc/sys/kernel/hung_task_timeout_secs
# cat /proc/sys/kernel/hung_task_timeout_secs
0


##### [C] THE CALL-TRACE

### [C.1] TRY TO FORCE THE CALL-TRACE

The call-trace is not ***always*** reproducible!
Even with "0" for "hung_task_timeout_secs" it is seen (see testcase #3)!

The call-trace ***always*** happened when the output "-su: echo: write
error: Device or resource busy" was seen!
Unsure, how to intpret it!
What means "-su"?
Write-error to which device?
Which resource is busy?

# LC_ALL=C echo mem > /sys/power/state && sleep 1
-su: echo: write error: Device or resource busy <--- THIS OUTPUT!

[ /var/log/kern.log ]

n 19 18:00:02 fambox kernel: [ 3065.559184] PM: Syncing filesystems ... done.
Jan 19 18:00:02 fambox kernel: [ 3065.768458] PM: Preparing system for mem sleep
Jan 19 18:00:14 fambox kernel: [ 3072.733178] Freezing user space
processes ... (elapsed 0.01 seconds) done.
Jan 19 18:00:14 fambox kernel: [ 3072.749284] Freezing remaining
freezable tasks ... (elapsed 0.01 seconds) done.
Jan 19 18:00:14 fambox kernel: [ 3072.765274] suspend debug: Waiting
for 5 seconds.
Jan 19 18:00:14 fambox kernel: [ 3077.722222] PM: Finishing wakeup.
Jan 19 18:00:14 fambox kernel: [ 3077.722224] Restarting tasks ... done.
Jan 19 18:00:14 fambox kernel: [ 3077.726719] video LNXVIDEO:00:
Restoring backlight state
Jan 19 18:00:18 fambox kernel: [ 3081.596512] PM: Syncing filesystems ... done.
Jan 19 18:00:18 fambox kernel: [ 3081.750235] PM: Preparing system for mem sleep
Jan 19 18:00:45 fambox kernel: [ 3087.738204] Freezing user space
processes ... (elapsed 0.04 seconds) done.
Jan 19 18:00:45 fambox kernel: [ 3087.786660] Freezing remaining
freezable tasks ...
Jan 19 18:00:45 fambox kernel: [ 3107.788540] Freezing of tasks failed
after 20.01 seconds (1 tasks refusing to freeze, wq_busy=0):
Jan 19 18:00:45 fambox kernel: [ 3107.788664] jbd2/loop0-8    D
ffffffff8180d780     0   299      2 0x00000000
Jan 19 18:00:45 fambox kernel: [ 3107.788673]  ffff88011822db68
0000000000000046 ffff88011822db08 ffffffff81044c29
Jan 19 18:00:45 fambox kernel: [ 3107.788682]  ffff880117c6dc80
ffff88011822dfd8 ffff88011822dfd8 ffff88011822dfd8
Jan 19 18:00:45 fambox kernel: [ 3107.788689]  ffffffff81c15440
ffff880117c6dc80 ffff88011822db68 ffff88011fa14738
Jan 19 18:00:45 fambox kernel: [ 3107.788696] Call Trace:
Jan 19 18:00:45 fambox kernel: [ 3107.788715]  [<ffffffff81044c29>] ?
default_spin_lock_flags+0x9/0x10
Jan 19 18:00:45 fambox kernel: [ 3107.788726]  [<ffffffff811c6830>] ?
__wait_on_buffer+0x30/0x30
Jan 19 18:00:45 fambox kernel: [ 3107.788735]  [<ffffffff816b7449>]
schedule+0x29/0x70
Jan 19 18:00:45 fambox kernel: [ 3107.788741]  [<ffffffff816b751f>]
io_schedule+0x8f/0xd0
Jan 19 18:00:45 fambox kernel: [ 3107.788748]  [<ffffffff811c683e>]
sleep_on_buffer+0xe/0x20
Jan 19 18:00:45 fambox kernel: [ 3107.788758]  [<ffffffff816b5d1f>]
__wait_on_bit+0x5f/0x90
Jan 19 18:00:45 fambox kernel: [ 3107.788765]  [<ffffffff811c5ef1>] ?
submit_bh+0x121/0x1e0
Jan 19 18:00:45 fambox kernel: [ 3107.788771]  [<ffffffff811c6830>] ?
__wait_on_buffer+0x30/0x30
Jan 19 18:00:45 fambox kernel: [ 3107.788779]  [<ffffffff816b5dcc>]
out_of_line_wait_on_bit+0x7c/0x90
Jan 19 18:00:45 fambox kernel: [ 3107.788787]  [<ffffffff8107eb00>] ?
autoremove_wake_function+0x40/0x40
Jan 19 18:00:45 fambox kernel: [ 3107.788794]  [<ffffffff811c682e>]
__wait_on_buffer+0x2e/0x30
Jan 19 18:00:45 fambox kernel: [ 3107.788805]  [<ffffffff8128c02c>]
jbd2_journal_commit_transaction+0x18cc/0x1d60
Jan 19 18:00:45 fambox kernel: [ 3107.788814]  [<ffffffff816b85de>] ?
_raw_spin_lock_irqsave+0x2e/0x40
Jan 19 18:00:45 fambox kernel: [ 3107.788823]  [<ffffffff81069fbf>] ?
try_to_del_timer_sync+0x4f/0x70
Jan 19 18:00:45 fambox kernel: [ 3107.788830]  [<ffffffff81290836>]
kjournald2+0xd6/0x3e0
Jan 19 18:00:45 fambox kernel: [ 3107.788835]  [<ffffffff8107eac0>] ?
add_wait_queue+0x60/0x60
Jan 19 18:00:45 fambox kernel: [ 3107.788841]  [<ffffffff81290760>] ?
commit_timeout+0x10/0x10
Jan 19 18:00:45 fambox kernel: [ 3107.788846]  [<ffffffff8107ded0>]
kthread+0xc0/0xd0
Jan 19 18:00:45 fambox kernel: [ 3107.788852]  [<ffffffff8107de10>] ?
flush_kthread_worker+0xb0/0xb0
Jan 19 18:00:45 fambox kernel: [ 3107.788859]  [<ffffffff816c0dec>]
ret_from_fork+0x7c/0xb0
Jan 19 18:00:45 fambox kernel: [ 3107.788865]  [<ffffffff8107de10>] ?
flush_kthread_worker+0xb0/0xb0
Jan 19 18:00:45 fambox kernel: [ 3107.788929]
Jan 19 18:00:45 fambox kernel: [ 3107.788932] Restarting kernel
threads ... done.
Jan 19 18:00:45 fambox kernel: [ 3107.789086] Restarting tasks ... done.
Jan 19 18:00:45 fambox kernel: [ 3107.802117] video LNXVIDEO:00:
Restoring backlight state

### [C.2] CHECKING DBUS AND RCU_SCHED STATUS POST-MORTEM

# ll /var/run/dbus/
insgesamt 4
drwxr-xr-x  2 messagebus messagebus  80 Jan 19 17:08 ./
drwxr-xr-x 22 root       root       800 Jan 19 17:11 ../
-rw-r--r--  1 root       root         4 Jan 19 17:08 pid
srwxrwxrwx  1 root       root         0 Jan 19 17:08 system_bus_socket=

# cat /var/run/dbus/pid
862

root@fambox:~# ps axu | grep -v grep | grep 862
102        862  0.0  0.0  25492  2332 ?        Ss   17:08   0:01
dbus-daemon --system --fork --activation=upstart
wearefam  1931  0.0  0.5 862752 20116 ?        Sl   17:09   0:02
/usr/lib/gnome-settings-daemon/gnome-settings-daemon

# pidof dbus-daemon
1921 862

# cat /proc/sys/kernel/hung_task_timeout_secs
0


##### [D] INTERIM SUMMARY

1. The issue is reproducible!
2. The issue ***can*** be forced by running pm_test/freezer!

Again, the root cause is not very clear to me!

Recent TTY-NEXT changes?
Problems in EXT4-FS/JBD2?
Problems in X86/RCU?

Ask the experts :-)!


-dileks // 19-Jan-2013

I have a applied another pending patch ("tty: Add driver unthrottle in
ioctl(...,TCFLSH,..).") from tty-next.

Now, the call-trace looks like this:

[  433.527986] PM: Syncing filesystems ... done.
[  433.843761] PM: Preparing system for mem sleep
[  436.306002] Freezing user space processes ...
[  456.304956] Freezing of tasks failed after 20.01 seconds (1 tasks
refusing to freeze, wq_busy=0):
[  456.305060] Cache I/O       D ffffffff8180d780     0  2132      1 0x00000004
[  456.305065]  ffff88007b9dfe18 0000000000000046 ffff88007b9dfdc8
0000000300000001
[  456.305069]  ffff880097e21720 ffff88007b9dffd8 ffff88007b9dffd8
ffff88007b9dffd8
[  456.305072]  ffff880119b32e40 ffff880097e21720 ffff88007b9dfe28
ffff880118077800
[  456.305076] Call Trace:
[  456.305085]  [<ffffffff816b7469>] schedule+0x29/0x70
[  456.305089]  [<ffffffff8129067d>] jbd2_log_wait_commit+0xcd/0x1a0
[  456.305094]  [<ffffffff8107eac0>] ? add_wait_queue+0x60/0x60
[  456.305098]  [<ffffffff812307a5>] ext4_sync_file+0x205/0x380
[  456.305103]  [<ffffffff811c43ad>] do_fsync+0x5d/0x90
[  456.305108]  [<ffffffff8119442b>] ? sys_write+0x6b/0xa0
[  456.305111]  [<ffffffff811c4790>] sys_fsync+0x10/0x20
[  456.305114]  [<ffffffff816c0edd>] system_call_fastpath+0x1a/0x1f
[  456.305122]
[  456.305124] Restarting tasks ... done.
[  456.315056] video LNXVIDEO:00: Restoring backlight state

JBD2/EX4FS problem?

- Sedat -

[1] http://git.kernel.org/?p=linux/kernel/git/gregkh/tty.git;a=patch;h=a1bf9584429d61b7096f93ae09325e1ba538e9e8

[ CC Eric Sandeen ]

Looks like the patch " jbd2: don't wake kjournald unnecessarily" from
Eric helps here.
Still trying to reproduce the issue... but looks good so far!

- Sedat -

[1] http://patchwork.ozlabs.org/patch/207237/