Re: [Xen-devel] pv 2.6.31 (kernel.org) and save/migrate fails, domU BUG

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2009-11-12 at 23:36 +0000, Jeremy Fitzhardinge wrote:
> On 11/10/09 02:08, Pasi Kärkkäinen wrote:
> > Hello,
> >
> > Jeremy: Here's summary about these save/restore problems
> > using upstream Linux 2.6.31.5 PV guest.
> >
> > For me:
> >     - I can "xm save" + "xm restore" UP guest, but I get non-fatal
> >       BUG in the guest kernel, see [1].
> >     - "xm save" fails for SMP guest with "failed to get the suspend evtchn 
> > port", see [2].
> >
> > For Dan:
> >     - "xm save" works for UP guest, but "xm restore" doesn't, giving
> >       infinite xen_sched_clock related dumps in the guest kernel, see [3].
> >     - "xm save" for SMP guest fails, it never ends. I suspect this
> >       is the same problem I'm seeing.
> >
> >
> > [1] non-fatal BUG on the guest kernel after "xm restore":
> > http://pasik.reaktio.net/xen/debug/dmesg-2.6.31.5-122.fc12.x86_64-saverestore.txt
> >   
> 
> Does this help:

It does for me. There's another dpm_resume_noirq(PMSG_RESUME) a little
later in do_suspend() which I think needs to be dropped as well.

I'm still seeing other problems with resume, the system is hung on
restore and the RCU stall detection logic is triggering, unfortunately
arch_trigger_all_cpu_backtrace is not Xen compatible (uses APIC
directly) so I don't get much useful info out of it. It's most likely a
symptom of the actual problem rather than a problem with RCU per-se
anyhow.

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 10d03d7..7b69a1a 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -43,7 +43,6 @@ static int xen_suspend(void *data)
        if (err) {
                printk(KERN_ERR "xen_suspend: sysdev_suspend failed: %d\n",
                        err);
-               dpm_resume_noirq(PMSG_RESUME);
                return err;
        }
 
@@ -69,7 +68,6 @@ static int xen_suspend(void *data)
        }
 
        sysdev_resume();
-       dpm_resume_noirq(PMSG_RESUME);
 
        return 0;
 }
@@ -108,6 +106,9 @@ static void do_suspend(void)
        }
 
        err = stop_machine(xen_suspend, &cancelled, cpumask_of(0));
+
+       dpm_resume_noirq(PMSG_RESUME);
+
        if (err) {
                printk(KERN_ERR "failed to start xen_suspend: %d\n", err);
                goto out;
@@ -119,8 +120,6 @@ static void do_suspend(void)
        } else
                xs_suspend_cancel();
 
-       dpm_resume_noirq(PMSG_RESUME);
-
 resume_devices:
        dpm_resume_end(PMSG_RESUME);
 



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