Changing sysctl values within the kernel?

Changing sysctl values within the kernel?

[David Johnson]

Hi all,

I'm working on a kernel module and want to change sysctl values (specifically 
stop-a and printk) in response to a hardware event.

Is there an accepted way of setting sysctl values within the kernel (I can't 
seem to find any other module doing this), or is it a completely silly idea?

Would it perhaps be better to instead create a sysfs node and let a userspace 
daemon worry about setting the sysctl values?

Any advice greatly appreciated!

David.

Re: Changing sysctl values within the kernel?

[Alexey Dobriyan]

On Sat, Nov 25, 2006 at 07:11:48PM +0000, David Johnson wrote:
> I'm working on a kernel module and want to change sysctl values (specifically
> stop-a and printk) in response to a hardware event.
>
> Is there an accepted way of setting sysctl values within the kernel (I can't
> seem to find any other module doing this),

Yes. Next in-kernel module changing sysctls will do it via

	stop_a_enabled = 1;
	console_loglevel = 8;

(be sure, variables in question are EXPORT_SYMBOL'ed)

> or is it a completely silly idea?

Without more details it's hard to tell.

> Would it perhaps be better to instead create a sysfs node and let a userspace
> daemon worry about setting the sysctl values?

Now _this_ is silly. sysctls already live in /proc/sys/, so you can open(2)
/proc/sys/kernel/printk and write(2) to it.

Re: Changing sysctl values within the kernel?

[David Johnson]

On Sunday 26 November 2006 20:38, you wrote:
> On Sat, Nov 25, 2006 at 07:11:48PM +0000, David Johnson wrote:
> >
> > Is there an accepted way of setting sysctl values within the kernel (I
> > can't seem to find any other module doing this),
>
> Yes. Next in-kernel module changing sysctls will do it via
>
> 	stop_a_enabled = 1;
> 	console_loglevel = 8;
>
> (be sure, variables in question are EXPORT_SYMBOL'ed)
>

Bah, I never thought it would be that simple!

>
> > Would it perhaps be better to instead create a sysfs node and let a
> > userspace daemon worry about setting the sysctl values?
>
> Now _this_ is silly. sysctls already live in /proc/sys/, so you can open(2)
> /proc/sys/kernel/printk and write(2) to it.

OK, I'll give that a miss then ;-)

Thanks for your help!

David.