On Mon, Oct 17, 2016 at 07:17:32PM -0400, Wenda Ni wrote:
> Dear all,
> 
> I am working on a kernel module that incorporate both pr_debug and
> pr_warn. I would like to see pr_debug messages from dmesg.
> 
> What I followed is to specify kernel parameter by saying "loglevel=7".
> This can be seen confirmed  from /proc/cmdline. But still, I donot get
> pr_debug level messages either from dmesg or from /var/log/messages. I
> also tried echo 7 > /proc/sys/kernel/printk. It does not return what I
> expect, either.
> 
> Let me know what I am missing. Thank you very much in advance.
> 
> Cheers,
> 
> Wenda Ni, Ph.D.
> 
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Hello Wenda,                                                                    
                                                                                
                                                                                
                                 
                                                                                
                                                                                
                                                                                
                                 
I encountered the same issue a while ago.                                       
                                                                                
                                                                                
                                 
As stated here: http://elinux.org/Debugging_by_printing                         
                                                                                
                                                                                
                                 
pr_debug is replaced with an empty statement unless the kernel is compiled      
                                                                                
                                                                                
                                 
with DEBUG. So if you just want to play with printing kernel debug logs,        
                                                                                
                                                                                
                                 
just define the DEBUG macro in your module source file for testing.             
                                                                                
                                                                                
                                 
                                                                                
                                                                                
                                                                                
                                 
I also observed that without a new line character at the end of the string      
                                                                                
                                                                                
                                 
passed to pr_debug, I could not find the log line in dmesg output. Not sure     
                                                                                
                                                                                
                                 
where this comes from.    

-- 
Thibaut SAUTEREAU

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