Date: Wed, 17 Nov 2010 03:20:12 +0000 From: Alexander Best <arundel@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: kldunload(8) returns 0, although it fail Message-ID: <20101117032012.GA93866@freebsd.org> In-Reply-To: <201011101717.51062.jhb@freebsd.org> References: <20101109114612.GA58585@freebsd.org> <20101110215839.GA74943@freebsd.org> <20101110220721.GA76154@freebsd.org> <201011101717.51062.jhb@freebsd.org>
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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. 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. 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! cheers. alex > > 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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