Hi!
> It would seem that swsusp doesn't properly suspend devices, or more
> precisely it wakes them up again before suspending the machine.
Yes, and that's okay.
What happens to devices during swsusp? They seem to be resumed
during system suspend?
A: That's correct. We need to resume them if we want to write image to
disk. Whole sequence goes like
Suspend part
~~~~~~~~~~~~
running system, user asks for suspend-to-disk
user processes are stopped
suspend(PMSG_FREEZE): devices are frozen so that they don't
interfere
with state snapshot
state snapshot: copy of whole used memory is taken with
interrupts disabled
resume(): devices are woken up so that we can write image to
swap
write image to swap
suspend(PMSG_SUSPEND): suspend devices so that we can power off
turn the power off
Resume part
~~~~~~~~~~~
(is actually pretty similar)
running system, user asks for suspend-to-disk
user processes are stopped (in common case there are none, but
with resume-from-initrd, noone k\nows)
read image from disk
suspend(PMSG_FREEZE): devices are frozen so that they don't
interfere
with image restoration
image restoration: rewrite memory with image
resume(): devices are woken up so that system can continue
thaw all user processes
--
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