Re: [Patch] bonding: fix potential deadlock in bond_uninit()

[Cong Wang]

Eric W. Biederman wrote:
> Amerigo Wang <amwang@xxxxxxxxxx> writes:
>
> > bond_uninit() is invoked with rtnl_lock held, when it does destroy_workqueue()
> > which will potentially flush all works in this workqueue, if we hold rtnl_lock
> > again in the work function, it will deadlock.
> >
> > So unlock rtnl_lock before calling destroy_workqueue().
>
> Ouch.  That seems rather rude to our caller, and likely very
> dangerous.


This is reasonable, because workqueue flush functions will potentially
call all the work functions which could take the same lock taken before
the flush call, thus deadlock.

> Is this a deadlock you actually hit, or is this something lockdep
> warned about?

It's only a lockdep warning.

> My gut feel says we need to move the destroy_workqueue into
> the network device destructor.

Oh, this seems a better idea, as long as the destructor are not called
with any locks holding.

Thanks!
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