[linux-pm] [RFC] ACPI vs device ordering on resume

Linus Torvalds torvalds at osdl.org
Wed Nov 15 08:47:22 PST 2006

On Wed, 15 Nov 2006, Len Brown wrote:
> So it looks like we need this sequence:
> enable_nonboot_cpus() /* INIT */
> finish()	/* _WAK */
> device_resume()

Can somebody remind me about this immediately after 2.6.19?

No way am I going to make that kind of a major ordering change right now, 
especially as the thing isn't apparently even a real regression (just more 
fallout from enabling MSI).

It would be good if people who are affected (and people in general that 
are interested in power management) would test out the patch.

In particular, this is an even bigger change than the one suggested by 
Stephen. It means, for example, that we will have device resume (and 
process thawing) being called when we're in SMP mode - and that may or may 
not have issues. So this is a really scary patch to me, no way in hell 
will I apply it right now.

But if people try it out, it would be good..

Btw, this is a clear example of where it might be good to start actively 
using the "early_resume" thing, and do PCI bus resume there. We might want 
to do early_resume _before_ calling the bios (I'm not at all convinced 
that the firmware will do the right thing without the PCI buses set up, 
for example), and _before_ thawing processes. Then, we might let 
individual devices do their "device resume" in the normal late resume 

Greg already carries the patch around for that PCI bus early resume thing, 
I think. 

We need to test these things.


diff --git a/kernel/power/main.c b/kernel/power/main.c
index 873228c..2989609 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -132,12 +132,12 @@ int suspend_enter(suspend_state_t state)
 static void suspend_finish(suspend_state_t state)
-	device_resume();
-	resume_console();
-	thaw_processes();
 	if (pm_ops && pm_ops->finish)
+	device_resume();
+	resume_console();
+	thaw_processes();

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