On Thu, 20 Sep 2007, Thomas Gleixner wrote:
>
> In meantime I figured out what's happening. The ordering in
> hibernate_snapshot() is wrong. It does:
Hmm. This is close to the ordering we have in STR too.
I have some dim memory of there being some ACPI reason why it had to be
done that way.
In fact, this was done in commit e3c7db621bed4afb8e231cb005057f2feb5db557,
long ago, by Rafael:
As indicated in a recent thread on Linux-PM, it's necessary to call
pm_ops->finish() before devce_resume(), but enable_nonboot_cpus() has to be
called before pm_ops->finish() (cf.
http://lists.osdl.org/pipermail/linux-pm/2006-November/004164.html). For
consistency, it seems reasonable to call disable_nonboot_cpus() after
device_suspend().
This way the suspend code will remain symmetrical with respect to the resume
code and it may allow us to speed up things in the future by suspending and
resuming devices and/or saving the suspend image in many threads.
The following series of patches reorders the suspend and resume code so that
nonboot CPUs are disabled after devices have been suspended and enabled before
the devices are resumed. It also causes pm_ops->finish() to be called after
enable_nonboot_cpus() wherever necessary.
Hmm?
It's entirely possible that that commit was simply just buggy, and we
should indeed move the CPU down/up to be early/late - we've fixed other
ordering issues since that commit went in. But this whole area is very
murky.
(Btw, the above commit message points to just my response with a testing
patch to the real email: the actual explanation of the INSANE ordering is
from Len Brown in
https://lists.linux-foundation.org/pipermail/linux-pm/2006-November/004161.html
and there Len claims that we *must* wake up CPU's early).
I personally think that the whole ACPI ordering requirements are just
insane, but the point of this email is to point these different
requirements out, and hopefully we can get something that works for
everybody.
Len added to Cc.
Len? Thomas wants to call 'disable_nonboot_cpus()' early, and
'enable_nonboot_cpus()' late. Can you explain why that is wrong?
Linus
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