Phantom sysctl

[mdf at FreeBSD.org]

On Mon, Nov 15, 2010 at 9:53 AM, Garrett Cooper <yanegomi at gmail.com> wrote:
>    According to SYSCTL_INT(9):
>
>     The SYSCTL kernel interfaces allow code to statically declare sysctl(8)
>     MIB entries, which will be initialized when the kernel module containing
>     the declaration is initialized.  When the module is unloaded, the sysctl
>     will be automatically destroyed.
>
>    The sysctl should be reaped when the module is unloaded. My dumb
> test kernel module [1] doesn't seem to do that though (please note
> that the OID test_int_sysctl is created, and not reaped... FWIW it's
> kind of bizarre that test_int_sysctl is created in the first place,
> given what I've seen when SYSCTL_* gets executed):
>
> toaster# kldload ./test_int_sysctl.ko
> toaster# sysctl -a | grep test
> test_int_sysctl: 0
> vfs.nfs_common.realign_test: 0
> debug.test_int_sysctl: 0
> toaster# sysctl test_int_sysctl
> sysctl: unknown oid 'test_int_sysctl'
> toaster# kldunload ./test_int_sysctl.ko
> toaster# sysctl -a | grep test
> test_int_sysctl: 0
> vfs.nfs_common.realign_test: 0

debug.test_int_sysctl did disappear, and that was the sysctl in the module:

SYSCTL_INT(_debug, OID_AUTO, test_int_sysctl, CTLFLAG_RW, &_sysctl, 0,
    "Test sysctl OID");

I am not sure where the other test_int_sysctl appeared from, but the
results of "sysctl test_int_sysctl" didn't change from before
kldunload to after.

Thanks,
matthew

> toaster# sysctl test_int_sysctl
> sysctl: unknown oid 'test_int_sysctl'
>
>    I've seen this behavior on 8.1-RELEASE (custom kernel, vanilla
> sources), and CURRENT r215254.
>    I'm compiling the kernel with SYSCTL_DEBUG (and added some missing
> error checking in the kern_sysctl.c code) to see if I can track down
> the resource issue, but in the meantime if someone more knowledgeable
> has some suggestions for what to do / where I should look, I'm all
> ears.
> Thanks!
> -Garrett
>
> 1. http://pastebin.com/n7d9bH8U
> _______________________________________________
> freebsd-hackers at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe at freebsd.org"
>