KLOGD loops continuously calling 'syslog' system call when prink is disabled

KLOGD loops continuously calling 'syslog' system call when prink is disabled

[Madhu R]

Hi All,

         when I disable printk(CONFIG_PRINTK=n) in the kernel config
(2.6.26-rc6),  the klogd  loops continuously calling the 'syslog'
system call. It consumes 99% of the cpu time ( using 'top' command ) .
I found similar problem in the kernel mailing list and a patch had
gone into the mainline kernel
http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-11/msg03317.html

         In the patch, it returns 'ENOSYS'' while calling 'syslog'
system call if printk is disabled. So the klogd keeps on calling this
'syslog' and returns ENOSYS and this process takes most of the CPU
time.


         Please clarify whether I am following correct procedure or
this is DEFAULT behavior of klogd.


Thanks,
madhu.

Re: KLOGD loops continuously calling 'syslog' system call when prink is disabled

[WANG Cong]

On Thu, 19 Jun 2008 18:39:10 +0530
"Madhu R" <tuxmadhu@gmail.com> wrote:

> Hi All,
> 
>          when I disable printk(CONFIG_PRINTK=n) in the kernel config
> (2.6.26-rc6),  the klogd  loops continuously calling the 'syslog'
> system call. It consumes 99% of the cpu time ( using 'top' command ) .
> I found similar problem in the kernel mailing list and a patch had
> gone into the mainline kernel
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-11/msg03317.html
> 
>          In the patch, it returns 'ENOSYS'' while calling 'syslog'
> system call if printk is disabled. So the klogd keeps on calling this
> 'syslog' and returns ENOSYS and this process takes most of the CPU
> time.
> 
> 
>          Please clarify whether I am following correct procedure or
> this is DEFAULT behavior of klogd.


IIRC, this is the fault of klogd. It doesn't check the return value
of syslog(2) (or klogclt(3), a wrapper in glibc) carefully.

If you can, please send a patch to sysklogd people.

Thanks.


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