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SubjectRe: [linux-pm] [GIT PULL] One more power management fix for 2.6.37
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On Wednesday, November 03, 2010, Dominik Brodowski wrote:
> > There's apparently an ordering problem with dpm_list_mtx and
> > socket->skt_mutex. Lockdep details appended.
> >
> > Dominik, Rafael? What's the proper locking order here, and
> > how do we fix this?
>
> Thanks for noting this; let's see:
>
> - We add a PCMCIA device holding skt_mutex, therefore we have the ordering
> (1) skt_mutex -> (2) dpm_list_mtx
>
> - If we're suspending, dpm_list_mtx is held, but we need to acquire
> skt_mutex as we modify some data being protected by skt_mutex
> (1) dpm_list_mtx -> (2) skt_mutex
>
> Rafael, any idea on how to solve this? How do other subsystems handle such
> an issue? Do they call device_add() with no locks held at all?

They usually do from what I can tell.

Also only a few of them implement the ->suspend_noirq() callback, which is the
one executed under dpm_list_mtx.

What exactly is protected by skt_mutex ?

Rafael



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