Debugging a Stall or a Freeze

[Salam Farhat]

I added the tracefs functionality to wrapfs.
wrapfs is a stackable file system that intercepts file system calls and
Tracefs basically records the VFS calls into a file on disk.
wrapfs worked fine its that when I added the logging functionality it
failed.

The issue I am having is that When I run a workload on the mounted file
system (wrapfs+tracefs) the system freezes. the mouse pointer does not even
move.

I set it up in virtual box and had the kernel dump the messages to a serial
port which I then read from my host OS. I did this following the
instructions on this page:
http://linuxdeveloper.blogspot.com/2012/05/debugging-linux-kernel-over-serial-port.html

When the guest OS freezes I get the following messages seen below. I would
like to know what is a good approach for debugging this issue. I am not
sure what a process stall is. Is that a deadlock?


[  780.357876] BUG: soft lockup - CPU#0 stuck for 22s!
[nautilus:1382]
[  780.361658] Process nautilus (pid: 1382, ti=dca12000 task=dc837230
task.ti=d)
[  780.361658]
Stack:
[  780.361658] Call
Trace:
[  780.361658] Code: 90 b8 43 64 03 c1 b9 40 64 03 c1 e9 49 ff ff ff 90 55
ba 0
[  808.356372] BUG: soft lockup - CPU#0 stuck for 22s!
[nautilus:1382]
[  808.360223] Process nautilus (pid: 1382, ti=dca12000 task=dc837230
task.ti=d)
[  808.360223]
Stack:
[  808.360223] Call
Trace:
[  808.360223] Code: ff ff 90 b8 43 64 03 c1 b9 40 64 03 c1 e9 49 ff ff ff
90 5
[  814.876223] INFO: rcu_sched detected stall on CPU 0 (t=15000
jiffies)
[  814.876223] Process nautilus (pid: 1382, ti=dca12000 task=dc837230
task.ti=d)
[  814.876223]
Stack:
[  814.876223] Call
Trace:
[  814.876223] Code: 00 c3 ff ff 80 e5 10 75 ee c1 e6 18 89 b0 10 c3 ff ff
89 d




Thanks.
Salam
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20130725/8b348a2a/attachment.html