Date:	Wed, 17 Jul 2013 09:30:21 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Lucas De Marchi <lucas.de.marchi@...il.com>,
	Philipp Hahn <pmhahn@...ahn.de>
Cc:	Takashi Iwai <tiwai@...e.de>, alsa-devel@...a-project.org,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>
Subject: Re: [alsa-devel] [BUG] 3.10.[01] modprobe snd-... hangs

Lucas De Marchi <lucas.de.marchi@...il.com> writes:
> On Tue, Jul 16, 2013 at 5:28 AM, Philipp Hahn <pmhahn@...ahn.de> wrote:
>> Hello,
>>
>> Am Dienstag 16 Juli 2013, 08:43:36 schrieb Takashi Iwai:
>>> At Tue, 16 Jul 2013 15:11:51 +0930, Rusty Russell wrote:
>>> > Philipp Matthias Hahn <pmhahn@...ahn.de> writes:
>>> > > My x86_64 systems has some trouble loading some ALSA snd-* modules since
>>> > > the upgrade to 3.10.[01]: Several automatic modprobe calls hang, but
>>> > > loading snd-intel-hda and snd-audio-usb by hand still works.
>>> >
>>> > Not a known problem to me, at least.  Perhaps it's a dep loop somehow.
>>>
>>> I remember that someone reported it being Debian specific snd-seq-oss
>>> loading stuff.
>>
>> FYI: "oss-compat" is installed.
>>
>>> > > ...
>>> > >  1071 ?        S      0:00 sh -c /sbin/modprobe --ignore-install snd && { /sbin/modprobe --quiet snd
>>> > >  1080 ?        D      0:00  \_ /sbin/modprobe --quiet snd-seq
>>> >
>>> > This was first, and it's waiting.  Which means it must be doing
>>> > something weird, because snd_seq_oss is loading now:
>>> >
>>> > > snd_seq_oss 33717 1 - Loading 0xffffffffa041b000
>>> >
>>> > Perhaps in the tangle of modprobe install commands somewhere this gets
>>> > invoked?
>>>
>>> Likely, but I wonder what triggered a bug suddenly on 3.10.
>>> There is absolutely no change in sound/core/seq/*, and through a quick
>>> look, I couldn't find any suspicious change in kernel/module.c that
>>> may lead to this problem between 3.9 and 3.10.
>>>
>>> Philipp, can you get a sysrq-T trace while the stall?
>>
>> I've finally been able to reducte the number of processes to get a full trace; see attached file.
>>
>> Please note that in this case the proprietary "nvidia" module was loaded, since I currently onyl have remove access to the machine.
>> The original trace from yesterday happend without the nvidia module ever being loaded.
>>
>> Am Dienstag 16 Juli 2013, 08:42:35 schrieb Lucas De Marchi:
>>> On Tue, Jul 16, 2013 at 2:41 AM, Rusty Russell <rusty@...tcorp.com.au> wrote:
>>> First thing to check is the /etc/modprobe.d/*.conf file that contains
>>> these install commands. Did they change besides the kernel upgrade?
>>
>> Not that I know of: Booting 3.9.9 works fine, 3.10.x shows the problem.
>
> Then one possible explanation is that in 3.9.9 you don't have some of
> the modules causing this problem
>
>>
>> ...
>>> Philipp, which kernel are you upgrading from?
>> I just upgraded from 3.9.9 to 3.10.0; also tried 3.10.1 which did not improve the situation.
>>
>>> I don't see anything to
>>> blame in the changes for the past releases. Any chance a bad entry in
>>> your .conf was added too? You may want to paste the output of modprobe
>>> -c, at least until "# End of configuration files. Dumping indexes
>>> now:"
>>
>> blacklist snd_pcsp
>> blacklist arkfb
>> blacklist aty128fb
>> blacklist atyfb
>> blacklist radeonfb
>> blacklist cirrusfb
>> blacklist cyber2000fb
>> blacklist gx1fb
>> blacklist gxfb
>> blacklist kyrofb
>> blacklist matroxfb_base
>> blacklist mb862xxfb
>> blacklist neofb
>> blacklist nvidiafb
>> blacklist pm2fb
>> blacklist pm3fb
>> blacklist s3fb
>> blacklist savagefb
>> blacklist sisfb
>> blacklist tdfxfb
>> blacklist tridentfb
>> blacklist viafb
>> blacklist vt8623fb
>> blacklist garmin_gps
>> blacklist nouveau
>> install binfmt_0000 /bin/true
>> install sound_slot_0 /sbin/modprobe snd-card-0
>> install sound_slot_1 /sbin/modprobe snd-card-1
>> install sound_slot_2 /sbin/modprobe snd-card-2
>> install sound_slot_3 /sbin/modprobe snd-card-3
>> install sound_slot_4 /sbin/modprobe snd-card-4
>> install sound_slot_5 /sbin/modprobe snd-card-5
>> install sound_slot_6 /sbin/modprobe snd-card-6
>> install sound_slot_7 /sbin/modprobe snd-card-7
>> install snd /sbin/modprobe --ignore-install snd && { /sbin/modprobe --quiet snd-ioctl32 ; /sbin/modprobe --quiet snd-seq ; : ; }
>> install snd_rawmidi /sbin/modprobe --ignore-install snd-rawmidi && { /sbin/modprobe --quiet snd-seq-midi ; : ; }
>> install snd_emu10k1 /sbin/modprobe --ignore-install snd-emu10k1 && { /sbin/modprobe --quiet snd-emu10k1-synth ; : ; }
>> alias net_pf_16_proto_1 wire
>> alias net_pf_16_proto_3 ip_queue
>> alias net_pf_16_proto_8 scsi_transport_iscsi
>> alias net_pf_16_proto_9 audit
>> alias net_pf_16_proto_11 cn
>> alias net_pf_16_proto_13 ip6_queue
>> alias binfmt_204 binfmt_aout
>> alias binfmt_263 binfmt_aout
>> alias binfmt_264 binfmt_aout
>> alias binfmt_267 binfmt_aout
>> alias binfmt_387 binfmt_aout
>> alias block_major_3_* ide_generic
>> alias block_major_22_* ide_generic
>> alias block_major_33_* ide_generic
>> alias block_major_34_* ide_generic
>> alias block_major_37_* ide_tape
>> alias block_major_44_* ftl
>> alias block_major_46_* pcd
>> alias block_major_47_* pf
>> alias block_major_56_* ide_generic
>> alias block_major_57_* ide_generic
>> alias block_major_58_* lvm_mod
>> alias block_major_88_* ide_generic
>> alias block_major_89_* ide_generic
>> alias block_major_90_* ide_generic
>> alias block_major_91_* ide_generic
>> alias block_major_93_* nftl
>> alias block_major_97_* pg
>> alias char_major_10_1 psmouse
>> alias char_major_10_139 openprom
>> alias char_major_10_157 applicom
>> alias char_major_10_181 toshiba
>> alias char_major_10_183 hw_random
>> alias char_major_10_187 irnet
>> alias char_major_10_189 ussp
>> alias char_major_10_250 hci_vhci
>> alias char_major_13_0 joydev
>> alias char_major_13_1 joydev
>> alias char_major_13_2 joydev
>> alias char_major_13_3 joydev
>> alias char_major_13_32 mousedev
>> alias char_major_13_33 mousedev
>> alias char_major_13_34 mousedev
>> alias char_major_13_35 mousedev
>> alias char_major_13_63 mousedev
>> alias char_major_13_64 evdev
>> alias char_major_13_65 evdev
>> alias char_major_13_66 evdev
>> alias char_major_13_67 evdev
>> alias char_major_19_* cyclades
>> alias char_major_20_* cyclades
>> alias char_major_22_* pcxx
>> alias char_major_23_* pcxx
>> alias char_major_27_* ftape
>> alias char_major_34_* scc
>> alias char_major_35_* tclmidi
>> alias char_major_48_* riscom8
>> alias char_major_49_* riscom8
>> alias char_major_57_* esp
>> alias char_major_58_* esp
>> alias char_major_63_* kdebug
>> alias char_major_67_* coda
>> alias char_major_75_* specialix
>> alias char_major_76_* specialix
>> alias char_major_81_* videodev
>> alias char_major_83_* vtx
>> alias char_major_89_* i2c_dev
>> alias char_major_90_* mtdchar
>> alias char_major_96_* pt
>> alias char_major_97_* pg
>> alias char_major_107_* 3dfx
>> alias char_major_109_* lvm_mod
>> alias char_major_166_* cdc_acm
>> alias char_major_171_0 raw1394
>> alias char_major_171_1 video1394
>> alias char_major_171_2 dv1394
>> alias char_major_171_3 amdtp
>> alias char_major_180_* usbcore
>> alias char_major_195_* nvidia
>> alias char_major_200_* vxspec
>> alias char_major_202_* msr
>> alias char_major_203_* cpuid
>> alias char_major_206_* osst
>> alias char_major_208_* ussp
>> alias char_major_227_* tub3270
>> alias bt_proto_7 avdtp
>> alias cipcb0 cipcb
>> alias cipcb1 cipcb
>> alias cipcb2 cipcb
>> alias cipcb3 cipcb
>> alias dummy0 dummy
>> alias dummy1 dummy
>> alias plip0 plip
>> alias plip1 plip
>> alias slip0 slip
>> alias slip1 slip
>> alias tunl0 ipip
>> alias gre0 ip_gre
>> alias usbdevfs usbcore
>> alias char_major_195* nvidia
>> options snd_pcsp index=-2
>> options snd_usb_audio index=-2
>> options bt87x index=-2
>> options cx88_alsa index=-2
>> options snd_atiixp_modem index=-2
>> options snd_intel8x0m index=-2
>> options snd_via82xx_modem index=-2
>> options snd_hda_intel model=6stack-dig index=0
>> options snd_usb_audio index=1
>> options dvb_ttpci adapter_nr=1
>> options budget_ci adapter_nr=0
>> options nbd max_part=15
>> options nvidia NVreg_DeviceFileUID=0 NVreg_DeviceFileGID=44 NVreg_DeviceFileMode=0660
>> options libata force=noncq
>> options systemd log_target=kmsg
>> softdep uhci_hcd pre: ehci-hcd
>> softdep ohci_hcd pre: ehci-hcd
>> softdep snd_pcm post: snd-pcm-oss
>> softdep snd_mixer post: snd-mixer-oss
>> softdep snd_seq post: snd-seq-midi snd-seq-oss
>
>
> hum... it looks like a loop between the modprobe calls and the
> request_module(), done in snd_seq's init. The request_module() call
> will end up trying to load snd_seq again and it will remain waiting on
> kernel/module.c:add_unformed_module().
>
> In kmod we don't trust a COMING state on sysfs to avoid calling
> (f)init_module() because a) the previous call may fail and b) it's
> racy.

Yes, add_unformed_module makes the same call.  I think the answer is
simply "don't do that".

> Changing the request_module() in the module to be async would solve
> the problem (what Takashi Iwai did)... but this has been a
> little controversial in the past.  Rusty, what do you think? Maybe in
> kmod we can take the COMING state into consideration for
> *dependencies*? Or is moving that call to a worker acceptable?

I thought about adding a post_init() call for modules for this kind of
thing, but it's actually pretty rare.  Open-coding it seems fine.

Cheers,
Rusty.
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