Re: [PATCH] Proposed fix for PM deadlock on dpm_sem

[Alan Stern]

On Mon, 11 Oct 2004, Paul Mackerras wrote:

> I have been having trouble with deadlocks on dpm_sem when suspending
> and resuming, particularly if I remove a usb device while my powerbook
> is suspended.  The dpm_sem deadlocks also mean that USB can't deal
> with devices whose drivers don't have suspend/resume callbacks by
> simply disconnecting the device, as it did in the past.  This meant
> that while I can get my dual G4 powermac desktop machine to suspend
> to ram and resume (using the powerbook sleep code), its USB keyboard
> wouldn't work after resume.

A while ago I posted some thoughts on locking in the driver model which 
are somewhat relevant here.  Please take a look at

http://marc.theaimsgroup.com/?l=linux-usb-devel&m=109596905805858&w=2

It doesn't address exactly the same issues you're concerned with, but it
does concern the way suspend/resume interacts with device
addition/removal.

Alan Stern

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