Re: [RFC] Add the "icebox"

[Johannes Berg <johannes@sipsolutions.net>]

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> The idea was that kernel threads would have a PM-notifier routine and
> would be sent to the icebox when the routine gets a
> PM_{HIBERNATION|SUSPEND|RESTORE}_PREPARE message.  Presumably the
> notifier routine wouldn't return until the thread was safely on its way
> to the icebox.
> 
> You are correct that this would require some additional locking, plus 
> the extra notifier routine, plus ways to handle timeouts, plus maybe 
> some other stuff.  That's why I said in my earlier message that 
> keeping the freezer around for these sorts of threads would be a good 
> idea -- it would avoid all this new overhead.

Ok, makes sense, thanks for the explanation.

> The icebox would still be useful, however, for user tasks that try to
> do I/O after a system-sleep transition has begun.  Right now this can't
> happen, thanks to the freezer (except that it _can_ happen on PPC where
> the freezer isn't used for suspend).  Once the freezer no longer
> affects user tasks, kernel drivers will have to do _something_ when a
> user task submits an I/O request during a system sleep.  That
> "something" will be to go to the icebox.

Right, ok. I wish I could change powerpc, I've been maintaining a patch
for months now, but Paul seems to be dead set against it. Not only does
that fix these things, but also we get to use the /sys/power/state
API...

johannes

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