printk() not outputting

wizumwalt · 10-03-2009, 03:55 PM

For some reason, my printk()'s aren't putting anything out to my /var/log/messages file. I am running X so, as I understand it, messages won't appear in the terminals where I insmod() the module. But they should appear in /var/log/messages.

If I load my test module, I do get a message from /var/log/messages saying ....

Code:

Oct  3 14:50:04 Tux sudo:   whisper : TTY=pts/12 ; PWD=/home/whisper/test-mod/kernel/net/tm ; USER=root ; COMMAND=/sbin/insmod tm.ko

I've placed printk()'s in module_init func with KERN_INFO, and KERN_CRIT, and still don't see anything. I do see that w/ lsmod, my module is loaded.

Any ideas?

estabroo · 10-04-2009, 09:38 AM

How are you loading your module? If you are using modprobe, are you putting your re-compiled module in the correct place and doing a depmod -a to rebuild the dependency file? What does your printk() look like, are you putting a \n at the end of the string, if not then it won't show up until later and it'll be mixed in with other messages.

wizumwalt · 10-04-2009, 01:38 PM

I've got it down to as simple as this ...

Code:

 
static int __init my_init(void) {
    printk(KERN_INFO "my_init ...\n");

    // ...

    return 0;
}                                                             

static void __exit my_exit(void) {
    printk(KERN_INFO "my_exit ...\n");
}

yaplej · 10-05-2009, 08:03 PM

I could not get "KERN_INFO" to work either. Try "KERN_ALERT", and see if it works.

wizumwalt · 10-05-2009, 09:03 PM

Quote:

Originally Posted by yaplej

I could not get "KERN_INFO" to work either. Try "KERN_ALERT", and see if it works.

Nope

Also, the values in my /proc/sys/kernel/printk file are:
1 4 1 7

So I changed the first value to 7, and I still didn't see messages in my /var/log/messages file, nor using dmesg.

estabroo · 10-06-2009, 11:59 AM

are you sure your loading a current version of your module?

wizumwalt · 10-06-2009, 09:57 PM

What else can you do to get your current module besides this ...

[code]
make
depmod -a
sudo insmod ./mymod.ko
[code]

Did you intend something other than './'?

estabroo · 10-07-2009, 12:42 AM

Did you rmmod the old module before doing your insmod?

wizumwalt · 10-07-2009, 07:20 PM

Quote:

Originally Posted by estabroo

Did you rmmod the old module before doing your insmod?

Heh, yeah, I know that much. But still a no go for some reason. I don't understand this.

estabroo · 10-08-2009, 08:02 PM

try KERN_WARN or KERN_CRIT, you can also check your syslog configuration, maybe its directly lower level stuff elsewhere

wizumwalt · 10-09-2009, 12:04 PM

Yeah, tried those already, and the syslog-ng.conf file looks fine.

Anisha Kaul · 11-19-2009, 04:01 AM

If you do not trust KERN_WARN, KERN_INFO or KERN_CRIT or anything similar to work properly, you can and should use printk without any of these,

i.e.
printk ("\nthank god\n");

Meanwhile can u show the exact code of your whole module !