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Re: [Xen-devel] [PATCH 00/60] xen: add core scheduling support



On 18.07.19 17:14, Sergey Dyasli wrote:
On 18/07/2019 15:48, Juergen Gross wrote:
On 15.07.19 16:08, Sergey Dyasli wrote:
On 05/07/2019 14:56, Dario Faggioli wrote:
On Fri, 2019-07-05 at 14:17 +0100, Sergey Dyasli wrote:
1) This crash is quite likely to happen:

[2019-07-04 18:22:46 UTC] (XEN) [ 3425.220660] Watchdog timer detects
that CPU2 is stuck!
[2019-07-04 18:22:46 UTC] (XEN) [ 3425.226293] ----[ Xen-4.13.0-
8.0.6-d  x86_64  debug=y   Not tainted ]----
[...]
[2019-07-04 18:22:47 UTC] (XEN) [ 3425.501989] Xen call trace:
[2019-07-04 18:22:47 UTC] (XEN) [
3425.505278]    [<ffff82d08023d578>] vcpu_sleep_sync+0x50/0x71
[2019-07-04 18:22:47 UTC] (XEN) [
3425.511518]    [<ffff82d080208370>] vcpu_pause+0x21/0x23
[2019-07-04 18:22:47 UTC] (XEN) [
3425.517326]    [<ffff82d08023e25d>]
vcpu_set_periodic_timer+0x27/0x73
[2019-07-04 18:22:47 UTC] (XEN) [
3425.524258]    [<ffff82d080209682>] do_vcpu_op+0x2c9/0x668
[2019-07-04 18:22:47 UTC] (XEN) [
3425.530238]    [<ffff82d08024f970>] compat_vcpu_op+0x250/0x390
[2019-07-04 18:22:47 UTC] (XEN) [
3425.536566]    [<ffff82d080383964>] pv_hypercall+0x364/0x564
[2019-07-04 18:22:47 UTC] (XEN) [
3425.542719]    [<ffff82d080385644>] do_entry_int82+0x26/0x2d
[2019-07-04 18:22:47 UTC] (XEN) [
3425.548876]    [<ffff82d08038839b>] entry_int82+0xbb/0xc0

Mmm... vcpu_set_periodic_timer?

What kernel is this and when does this crash happen?

Hi Dario,

I can easily reproduce this crash using a Debian 7 PV VM (2 vCPUs, 2GB RAM)
which has the following kernel:

# uname -a

Linux localhost 3.2.0-4-amd64 #1 SMP Debian 3.2.78-1 x86_64 GNU/Linux

All I need to do is suspend and resume the VM.

Happens with a more recent kernel, too.

I can easily reproduce the issue with any PV guest with more than 1 vcpu
by doing "xl save" and then "xl restore" again.

With the reproducer being available I'm now diving into the issue...

One further thing to add is that I was able to avoid the crash by reverting

        xen/sched: rework and rename vcpu_force_reschedule()

which is a part of the series. This made all tests with PV guests pass.

Another question I have is do you have a git branch with core-scheduling
patches rebased on top of current staging available somewhere?

I have now a git branch with the two problems corrected and rebased to
current staging available:

github.com/jgross1/xen.git sched-v1b


Juergen

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