Hi Peter, Accidentally I came upon this article: http://stackframe.blogspot.com/2007/04/debugging-linux-kernels-with.html With the help of it I could get a stacktrace when the kernel hung. The problem was a stupid one: I was holding a spin_lock and then I called some function that again tries to hold the same lock. Now I release the lock before I call that method. I was working with mm/thrash.c But now I am getting a "BUG: spinlock recursion on CPU#0" error. What does this error mean ? Does it mean again it's spinning indefinitely on a spinlock ? I got the following backtrace: #0 0xc0505f1b in delay_tsc (loops=1) at arch/x86/lib/delay.c:85 #1 0xc0505f77 in __udelay (usecs=3479683981) at arch/x86/lib/delay.c:118 #2 0xc700ad98 in ?? () #3 0xc05097ba in _raw_spin_lock (lock=0xc6c34998) at lib/spinlock_debug.c:116 #4 0xc0647509 in _spin_lock_bh (lock=0xc6c349a8) at kernel/spinlock.c:113 #5 0xc048189e in dmam_pool_match (dev=<value optimized out>, res=0x1cb, match_data=0x0) at mm/dmapool.c:457 #6 0x00000001 in ?? () While writing this mail I had paused my guest OS kernel from gdb (^c) for sometime and when I said continue (c) it printed: "Clocksource tsc unstable (delta = 838972636559 ns) Regards, Sukanto Ghosh On Wed, Feb 18, 2009 at 4:52 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > Would u like to share WHERE u made the change? WHAT u do could be part of > academic exercise, so perhaps u want to keep confidential, but WHERE would > be helpful. > > I am suspecting (very usual for changes to MM codes) that u have done > something illegal while holding a open spinlock. So knowing where u insert > codes, will help us to understand if this is a problem or not. > > On Sat, Feb 14, 2009 at 7:52 PM, Sukanto Ghosh <sukanto.cse.iitb@xxxxxxxxx> > wrote: >> >> Hi, >> >> I have made some changes to the memory management part of the kernel >> as an experiment. Now when I boot into that kernel and start some >> heavy processes (which cause paging), the kernel hangs. I can't even >> type anything. >> >> I have gone through the 'paper on debugging kernel oops or hang' >> (http://mail.nl.linux.org/kernelnewbies/2003-08/msg00347.html) >> >> In this paper Erik says that to get the stack trace we can type >> 'Alt-SysRq-t' which prints the stack trace and when it's not possible >> to type anything, then it's best to use serial port + console. he says >> the config for lilo would be: console=ttyS0,9600 console=tty0 >> >> As I have grub I am using the following lines: >> >> default=0 >> timeout=15 >> title Fedora (2.6.27.4) >> root (hd0,0) >> kernel /boot/vmlinuz-2.6.27.4 ro root=/dev/sda1 >> initrd /boot/initrd-2.6.27.4.img >> serial --unit=0 --speed=9600 --word=8 --parity=no --stop=1 >> terminal --dumb --timeout=10 serial console >> >> >> >> CONFIG_MAGIC_SYSRQ was enabled in my config file. >> >> My test kernel is running inside a Virtual machine (VM) (VMware), with >> its serial port 0 redirected to a file. >> VM OS: fedora Core 9 with modified kernel 2.6.27.4 >> Host OS: ubuntu hardy 2.6.24.3 >> >> My problem is I am not getting any kind of output in the file to which >> I redirected the serial port of the VM except a bunch of "Press any >> key to continue .. " messages. >> >> should I be providing the 'alt-sysrq-t' input through the serial port, >> if so, how ? >> can i connect a host terminal to the serial port of the VM. >> Vmware gives me three options about the serial port of the Virtual Machine >> i) connect it to physical port of the host, ii) connect to a named >> pipe and, iii)connect it to a file in the host. >> >> Please help ... >> >> >> -- >> Regards, >> Sukanto Ghosh >> >> -- >> To unsubscribe from this list: send an email with >> "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx >> Please read the FAQ at http://kernelnewbies.org/FAQ >> > > > > -- > Regards, > Peter Teoh > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
