Re: Should suspend plug low-level devices?

[Tejun Heo <tj@kernel.org>]

Hello,

On Fri, Mar 18, 2016 at 05:06:01PM -0400, Alan Stern wrote:
> The original problem here was that some unfreezable code was waiting
> (via flush_delayed_work) on frozen code, and it was blocking the
> routine that would unfreeze things.  Therefore the order of freezing or
> thawing has no bearing on this particular problem.

Yeah, this one is caused by a high-level kernel construct being frozen
and device resuming as a whole taking place before unfreezing.  The
eventual goal would be avoiding freezing any high-level kernel
constructs as it can lead to circular dependencies as shown here.

> Now, I have nothing against finer-grained control of freezing, although
> I'm not sure how you would implement it in cases where a kthread is not
> per-device but rather is per-driver or per-subsystem.  But we will 
> still have to handle inversions where unfreezable code is waiting for 
> frozen code.

It won't be simple one-to-one conversion for all cases.  It's about
terminating suspend handling where the endpoints actually are after
all.

thanks.

-- 
tejun