Re: [Xen-users] [BUG] Xen BUG at sched_credit.c:243

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Mon, 2015-02-23 at 09:46 +0000, Ian Campbell wrote:
> (Just CCing some scheduler folks...)
> 
Thanks Ian,

> On Fri, 2015-02-20 at 20:19 -0600, C. B. wrote:
> > I am running Xen 4.5 on a Minnowboard MAX embedded board. 2GB ram,
> > dual core X86 cpu.  I have been running in to the following bug which
> > seems to usually trigger around 20-30 hours after first boot, but I
> > have seen it appear as quickly as 1 hour on one occasion.  This crash
> > info is from the serial console which was sat at the login prompt. As
> > far as I know nothing particularly strenuous is going on when this
> > occurs.
> > 
> > The dom0 is 3.18.7 with a custom compiled kernel. All of the running
> > domU images are also 3.18.7. To get the dom-0 kernel to boot under xen
> > I had to use acpi=off and make use of xen.efi.
>
I see. And you've done the right thing in providing all these info! :-)
I don't think these things about Dom0 have any influence in the repoted
issue. However, since you're building Dom0, let me ask this: are you
also building Xen from sources, or are you running it out of some distro
package? If you're not building it, could you (e.g., to test debug
patches, etc)?

> > I have put debug=y on the xen command line for the next crash, is
> > there anything else I can do to help myself report this in a useful
> > way?
> > 
I've never used 'debug=y' on Xen's command line. What I usually put
there in these cases is "loglvl=all guest_loglvl=all". Do you perhaps
mean _building_ Xen with debug=y? Because, if yes, that could be
helpful... Actually, the reason why I asked whether it could be possible
for you to build Xen was to then ask whether you could build it with
'debug=y'

> > base login: (XEN) Xen BUG at sched_credit.c:243
> > (XEN) ----[ Xen-4.5.0  x86_64  debug=n  Not tainted ]----
>
That's it: "debug=n". But you have to rebuild Xen to change this,
AFAICT.

> > (XEN) CPU:    0
> > (XEN) RIP:    e008:[<ffff82d08022934d>] __runq_insert.part.4+0/0x2
> > (XEN) RFLAGS: 0000000000010006   CONTEXT: hypervisor
> > (XEN) rax: ffff82d080498160   rbx: ffff830079ac5d20   rcx: 0000000000000000
> > (XEN) rdx: 0000000000000000   rsi: ffff830079ac5d80   rdi: 00005becb74182a1
> > (XEN) rbp: 0000000000000000   rsp: ffff82d080457d68   r8:  00005becb74160e1
> > (XEN) r9:  ffff82d080498180   r10: 00005becb7b7be39   r11: ffff830079da6d40
> > (XEN) r12: ffff82d080498160   r13: 0000000000000000   r14: ffff830079ac5d80
> > (XEN) r15: ffff82d080482620   cr0: 000000008005003b   cr4: 00000000001026f0
> > (XEN) cr3: 0000000063aee000   cr2: ffff8800162fd040
> > (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e010   cs: e008
> > (XEN) Xen stack trace from rsp=ffff82d080457d68:
> > (XEN)    ffff82d08011fc55 ffff82d080498ea0 ffff83007a4b72e0 ffff82d080498ea0
> > (XEN)    ffff82d080450000 0000000000000001 ffff82d080482620 ffff82d08022444a
> > (XEN)    ffff82d080482620 ffff830079b31790 ffff82d080450000 ffff82d080457e88
> > (XEN)    00005becb74182a1 0000001e00000000 ffff83007809a060 00000000000000af
> > (XEN)    0000000000000000 0000000000000003 0000000000000046 ffff82d08012cc5b
> > (XEN)    0000000000000086 0000000000000000 ffff82d0804981a8 0000000000000282
> > (XEN)    ffff8300799cd000 ffff82d080498160 ffff82d080498168 00005becb74182a1
> > (XEN)    ffff82d080498160 ffff82d080482620 ffff82d0801269c3 ffff830000000000
> > (XEN)    ffff82d080498180 00000000ffffffff ffff82d0801a98bb ffff830079da6000
> > (XEN)    ffffffff81c03ce8 ffff8300799cd000 ffffffffffffffff 0000009000000363
> > (XEN)    00000000ffffffff ffff82d08046f700 ffffffffffffffff ffff82d080450000
> > (XEN)    0000000000000001 ffff82d080482620 ffff82d080129b55 ffff83007809a000
> > (XEN)    ffff82d080450000 ffff83007809a000 00000000ffffffff ffff82d080482620
> > (XEN)    ffff82d08015fdd5 ffff8300799cd000 ffffffff81c03fd8 00000000ffffffed
> > (XEN)    ffffffff81c03fd8 0000000000000000 ffffffff81c03e48 0000000000000000
> > (XEN)    0000000000000246 0000000000007ff0 0000000000000000 0000000000000000
> > (XEN)    0000000000000000 ffffffff810013aa 0000000000000000 0000000000000000
> > (XEN)    0000000000000001 0000010000000000 ffffffff810013aa 000000000000e033
> > (XEN)    0000000000000246 ffffffff81c03e30 000000000000e02b 0000000000000000
> > (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
> > (XEN) Xen call trace:
> > (XEN)    [<ffff82d08022934d>] __runq_insert.part.4+0/0x2
> > (XEN)    [<ffff82d08011fc55>] csched_schedule+0x855/0x8a0
> > (XEN)    [<ffff82d08022444a>] common_interrupt+0x5a/0x60
> > (XEN)    [<ffff82d08012cc5b>] add_entry+0x4b/0xb0
> > (XEN)    [<ffff82d0801269c3>] schedule+0xf3/0x590
> > (XEN)    [<ffff82d0801a98bb>] mwait_idle+0x25b/0x350
> > (XEN)    [<ffff82d080129b55>] __do_softirq+0x65/0xa0
> > (XEN)    [<ffff82d08015fdd5>] idle_loop+0x25/0x50
> > (XEN)
> > (XEN)
> > (XEN) ****************************************
> > (XEN) Panic on CPU 0:
> > (XEN) Xen BUG at sched_credit.c:243
> > (XEN) ****************************************
> > (XEN)
> > (XEN) Manual reset required ('noreboot' specified)
> > 
Weird. I've never seen this before, TBH. You said you're on 4.5. Have
you used earlier version of Xen? If yes, was this bug there?

I'll take a look. In the meanwhile, if you can setup a debug build and,
when the bug manifests, send the stack trace again, that would
(hopefully) help.

Regards,
Dario

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