Messages in this thread | | | From | David Brownell <> | Subject | Re: [linux-pm] Fundamental flaw in system suspend, exposed by freezer removal | Date | Tue, 26 Feb 2008 01:16:17 -0800 |
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On Tuesday 26 February 2008, David Newall wrote: > > Hardware can be inserted and removed while we're in a suspend state; and > there's nothing that we can do about it until we resume. Is it fair to > say, then, that having started suspend, we could reasonably ignore any > device insertion and removal, and handle it on resume?
"Ignore" seems a bit strong; those events may be wakeup triggers, which would cause the hardware to make it a very short suspend state.
"Defer handling" is more to the point, be it by hardware or software.
> Presumably we need to scan for hardware changes on resume.
Not on most busses I work with; the hardware issues notifications whenever the devices are removable.
Which is a Good Thing ... scanning, as you suggest, is inherently not reliable. If a mouse is swapped, it likely doesn't matter a lot whether it's the "same" or not.
But ... how about if some removable storage media was taken out, updated on a different system, then restored before the resume? Not many filesystems handle that sanely. You *really* want to have hardware which reports disconnect/reconnect events, or which physically prevents them (locked case etc).
- Dave
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