Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 08 May 2013 18:15:33 +0200 | From | Takashi Iwai <> | Subject | Re: [PATCH 2/3] firmware: Avoid deadlock of usermodehelper lock at shutdown |
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At Wed, 8 May 2013 23:56:51 +0800, Ming Lei wrote: > > On Wed, May 8, 2013 at 2:56 PM, Takashi Iwai <tiwai@suse.de> wrote: > > When a system goes to reboot/shutdown, it tries to disable the > > usermode helper via usermodehelper_disable(). This might be blocked > > when a driver tries to load a firmware beforehand and it's stuck by > > some reason. > > IMO, it is better to find why the loading is stuck. Also we already provides > the timeout sysfs file to help to deal with the situation.
The loading is done manually in the case of dell_rbu driver, so it may happen at any time that the f/w loading doesn't finish properly.
> > In this patch, the firmware class driver registers a reboot notifier > > so that it can abort all pending f/w bufs. Also enable a flag for > > avoiding the call of usermodehelper after the reboot/shutdown starts. > > With this patch, maybe we only hide the real problem.
No, you can simulate the hang easily. Try the below (you can run it on every x86 machine; it just loads the data onto the memory.)
- modprobe dell_rbu
- echo init > /sys/devices/platform/dell_rbu/image_type
(... now /sys/class/firmware/dell_rbu/* appear)
- echo 1 > /sys/class/firmware/dell_rbu/loading
- halt -p
Now the machine gets stuck.
Yes, the real problem is obvious: you didn't finish the f/w loading in the above, and it will never happen. This doesn't justify that the machine can be stalled at shutdown, though.
Takashi
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