Re: Hung task when calling clone() due to netfilter/slab

[ebiederm@xmission.com (Eric W. Biederman)]

Christoph Lameter <cl@linux.com> writes:

> On Thu, 19 Jan 2012, Eric W. Biederman wrote:
>
>> On the flip side removing from sysfs with locks held must be done
>> carefully, and as a default I would recommend not to hold locks over
>> removing things from sysfs.  As removal blocks waiting for all of the
>> callers into sysfs those sysfs attributes to complete.
>>
>> It looks like you are ok on the removal because none of the sysfs
>> attributes appear to take the slub_lock, just /proc/slabinfo.  But
>> it does look like playing with fire.
>
> Ok then I guess my last patch is needed to make sysfs operations safe.
>
> It may be good to audit the kernel for locks being held while calling
> sysfs functions. Isnt there a lockdep check that ensures that no locks are
> held?

I don't see a no locks are held check but call_usermodehelper in the
blocking case could certainly use one.

For the sysfs remove case lockdep should work.

Eric

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