On Wed Nov 17 10, John Baldwin wrote:
> On Tuesday, November 16, 2010 10:20:12 pm Alexander Best wrote:
> > On Wed Nov 10 10, John Baldwin wrote:
> > > On Wednesday, November 10, 2010 5:07:21 pm Alexander Best wrote:
> > > > On Wed Nov 10 10, Alexander Best wrote:
> > > > > On Tue Nov 9 10, John Baldwin wrote:
> > > > > > On Tuesday, November 09, 2010 9:10:28 am Alexander Best wrote:
> > > > > > > On Tue Nov 9 10, John Baldwin wrote:
> > > > > > > > On Tuesday, November 09, 2010 6:46:12 am Alexander Best wrote:
> > > > > > > > > hi there,
> > > > > > > > >
> > > > > > > > > i posted this message on freebsd-questions@, but nobody could
> > > > > > > > > help me with it.
> > > > > > > > > to me this looks like a bug, so i assume posting it again
> > > > > > > > > here on
> > > > > > > > > freebsd-current@ might be better.
> > > > > > > > >
> > > > > > > > > please keep in mind that the issue here is not the fact that
> > > > > > > > > the second attempt
> > > > > > > > > to unload sound.ko/netgraph.ko fails. it *should* fail,
> > > > > > > > > because both modules
> > > > > > > > > have dependencies. however it should fail with the first
> > > > > > > > > attempt. right now
> > > > > > > > > kldunloadf() returns zero, whereas it should actually return
> > > > > > > > > EBUSY (just like
> > > > > > > > > the second attempt).
> > > > > > > > >
> > > > > > > > > i've attached two kdump outputs: one for the first
> > > > > > > > > 'kldunload' attempt and one
> > > > > > > > > for the second. as you can see the problem is that for some
> > > > > > > > > reason kldunloadf()
> > > > > > > > > returns zero, although it couldn't unload the module.
> > > > > > > >
> > > > > > > > Did you get an error message in dmesg? If you have manually
> > > > > > > > loaded
> > > > > > > > netgraph.ko (via netgraph_load="YES" in loader.conf or an
> > > > > > > > explicit kldload)
> > > > > > > > and then loaded other modules that depend on it (such as
> > > > > > > > ng_foo.ko) then this
> > > > > > > > is expected behavior. What your kldunload has done is to
> > > > > > > > remove the manual
> > > > > > > > reference from loader.conf or 'kldload netgraph.ko'. What this
> > > > > > > > changes is what
> > > > > > > > happens when you do 'kldunload ng_foo.ko'. If you unload
> > > > > > > > ng_foo.ko now, then
> > > > > > > > netgraph.ko will also be unloaded when its last reference drops
> > > > > > > > (in this case
> > > > > > > > it looks like you actually have two ng_*.ko objects loaded, so
> > > > > > > > you would have
> > > > > > > > to unload both of them, but I will assume a single ng_foo.ko to
> > > > > > > > make the
> > > > > > > > explanation simpler). If you had not done 'kldunload
> > > > > > > > netgraph.ko' but had
> > > > > > > > done 'kldunload ng_foo.ko', then the manual reference would
> > > > > > > > have kept netgraph.ko
> > > > > > > > loaded.
> > > > > > > >
> > > > > > > > All this logic exists so that if you do 'kldload foo.ko' and it
> > > > > > > > auto-loads bar.ko
> > > > > > > > as a dependency, then doing 'kldunload bar.ko' will unload both
> > > > > > > > foo.ko and bar.ko.
> > > > > > >
> > > > > > > i have ng_ubt_load="YES" in my loader.conf and kldstat says:
> > > > > > >
> > > > > > > Id Refs Address Size Name
> > > > > > > 1 37 0xffffffff80100000 a2ddb8 kernel
> > > > > > > 2 1 0xffffffff80b2e000 295e8 snd_hda.ko
> > > > > > > 3 1 0xffffffff80b58000 85110 sound.ko
> > > > > > > 4 1 0xffffffff80bde000 cf79e0 nvidia.ko
> > > > > > > 5 5 0xffffffff818d6000 418c0 linux.ko
> > > > > > > 6 1 0xffffffff81918000 80e8 ng_ubt.ko
> > > > > > > 7 2 0xffffffff81921000 fa78 ng_hci.ko
> > > > > > > 8 2 0xffffffff81931000 2bd0 ng_bluetooth.ko
> > > > > > > 9 3 0xffffffff81934000 15e68 netgraph.ko
> > > > > > > 10 1 0xffffffff81a12000 3efb linprocfs.ko
> > > > > > > 11 3 0xffffffff81a16000 4698 pseudofs.ko
> > > > > > > 12 1 0xffffffff81a1b000 31b3 procfs.ko
> > > > > > > 13 1 0xffffffff81a1f000 a37 linsysfs.ko
> > > > > > > 14 1 0xffffffff81a20000 6f4 rtc.ko
> > > > > > >
> > > > > > > also the same happens with sound.ko. i have snd_hda_load="yes".
> > > > > > > and i think
> > > > > > > snd_hda is the only dependecy for sound.ko.
> > > > > > >
> > > > > > > there was no error message in dmesg for the first kldunload
> > > > > > > attempt.
> > > > > > >
> > > > > > > i think i understand the logic, however the current behavior does
> > > > > > > not confirm
> > > > > > > to the description in kldunload(2).
> > > > > >
> > > > > > Hmm, ok, fair enough. Do you get the same behavior if you kldload
> > > > > > ng_ubt.ko
> > > > > > after boot?
> > > >
> > > > just tested and the behavior is *not* the same. when i do kldload
> > > > ng_ubt after
> > > > boot everything seems fine. netgraph gets loaded and has a REF count of
> > > > 2. if i
> > > > try doing `kldunload netgraph` i get EBUSY the first time i run that
> > > > command.
> > > > when i add ng_ubt_load=yes to /boot/loader.conf kldstat reports a REF
> > > > count of
> > > > 3 for netgraph.ko and i get the behavior i described beforehand.
> > >
> > > Try doing 'kldload netgraph.ko' and then 'kldload ng_ubt.ko' (along with
> > > manually
> > > loading any other netgraph modules so that nothing is loaded magically as
> > > a
> > > dependency) and see what behavior that gives you.
i did some more research regarding this matter:
1) DEPENDENCIES:
netgraph => X (none)
ng_ubt => ng_hci
ng_hci => ng_bluetooth
ng_buetooth => X (none; [no not even netgraph])
2) VARIOUS results:
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 1
**
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldload ng_bluetooth => REF_COUNT_NETGRAPH = 1
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 1
(obvious, since ng_bluetooth doesn't depend on netgraph)
**
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldload ng_bluetooth => REF_COUNT_NETGRAPH = 1
kldload ng_hci => REF_COUNT_NETGRAPH = 2
kldunload netgraph => OK, REF_COUNT_NETGRAPH = 1
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 1 [1]
**
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldload ng_bluetooth => REF_COUNT_NETGRAPH = 1
kldload ng_hci => REF_COUNT_NETGRAPH = 2
kldload ng_ubt => REF_COUNT_NETGRAPH = 3
kldunload netgraph => OK, REF_COUNT_NETGRAPH = 2
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 2 [1]
**
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldload ng_bluetooth => REF_COUNT_NETGRAPH = 1
kldload ng_hci => REF_COUNT_NETGRAPH = 2
kldunload netgraph => OK, REF_COUNT_NETGRAPH = 1
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 1 [1]
kldload ng_ubt => REF_COUNT_NETGRAPH = 2
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 2 [1]
**
**
kldload netgraph => REF_COUNT_NETGRAPH = 1
kldload ng_bluetooth => REF_COUNT_NETGRAPH = 1
kldload ng_hci => REF_COUNT_NETGRAPH = 2
kldunload netgraph => OK, REF_COUNT_NETGRAPH = 1
kldload ng_ubt => REF_COUNT_NETGRAPH = 2
kldunload netgraph => EBUSY, REF_COUNT_NETGRAPH = 2 [1]
**
[1] before EBUSY gets returned i see a notice that netgraph.ko cannot be
unloaded, since it was loaded by the kernel. this doesn't happen in the
last two cases.
> >
> > sorry it took me a while to check this out. i did some more research and it
> > seems a few things are broken:
> >
> > 1) i have snd_hda in my loader.conf which will load sound as a dependency.
> > unloading snd_hda should then automatically unload sound, which it
> > *doesn't*.
> > i need to unload sound manually.
>
> I clearly said earlier that this is what happens. It's the paragraph below
> where I said that the kernel has no idea when it discovers the modules that
> the loader loaded which ones were explicit and which ones were implicit. It
> treats them all as explicit.
i'm really sorry. i completely forgot about that fact. so to make this easy for
me to finally comprehend:
if a module is loaded via loader.conf *no* implicit dependencies are present
and unloading a module from a chain that got triggered by loader.conf will
*never* unload anything except that one module i specified!
> >
> > 2) if i unload all ng_* modules i should then be able to also unload
> > netgraph,
> > because no dependencies are left. however kldunload fails with EBUSY!
>
> Perhaps netgraph.ko is not unloadable in general? Actually, that is exactly
> what
> it does:
>
> case MOD_UNLOAD:
> /* You can't unload it because an interface may be using it. */
> error = EBUSY;
> break;
>
> (from ng_base.c).
>
> > > When you load modules from the loader, they and all their dependencies are
> > > treated as if you had manually loaded them similar to kldload. This
> > > because
> > > the kernel can't determine which modules loaded by the loader were silent
> > > dependencies.
>
> --
> John Baldwin
--
a13x
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