On 06/02/2020 11:05, Sergey Dyasli wrote:
> On 06/02/2020 09:57, Jürgen Groß wrote:
>> On 05.02.20 17:03, Sergey Dyasli wrote:
>>> Hello,
>>>
>>> I'm currently investigating a Live-Patch application failure in core-
>>> scheduling mode and this is an example of what I usually get:
>>> (it's easily reproducible)
>>>
>>> (XEN) [ 342.528305] livepatch: lp: CPU8 - IPIing the other 15 CPUs
>>> (XEN) [ 342.558340] livepatch: lp: Timed out on semaphore in CPU
>>> quiesce phase 13/15
>>> (XEN) [ 342.558343] bad cpus: 6 9
>>>
>>> (XEN) [ 342.559293] CPU: 6
>>> (XEN) [ 342.559562] Xen call trace:
>>> (XEN) [ 342.559565] [<ffff82d08023f304>] R
>>> common/schedule.c#sched_wait_rendezvous_in+0xa4/0x270
>>> (XEN) [ 342.559568] [<ffff82d08023f8aa>] F
>>> common/schedule.c#schedule+0x17a/0x260
>>> (XEN) [ 342.559571] [<ffff82d080240d5a>] F
>>> common/softirq.c#__do_softirq+0x5a/0x90
>>> (XEN) [ 342.559574] [<ffff82d080278ec5>] F
>>> arch/x86/domain.c#guest_idle_loop+0x35/0x60
>>>
>>> (XEN) [ 342.559761] CPU: 9
>>> (XEN) [ 342.560026] Xen call trace:
>>> (XEN) [ 342.560029] [<ffff82d080241661>] R _spin_lock_irq+0x11/0x40
>>> (XEN) [ 342.560032] [<ffff82d08023f323>] F
>>> common/schedule.c#sched_wait_rendezvous_in+0xc3/0x270
>>> (XEN) [ 342.560036] [<ffff82d08023f8aa>] F
>>> common/schedule.c#schedule+0x17a/0x260
>>> (XEN) [ 342.560039] [<ffff82d080240d5a>] F
>>> common/softirq.c#__do_softirq+0x5a/0x90
>>> (XEN) [ 342.560042] [<ffff82d080279db5>] F
>>> arch/x86/domain.c#idle_loop+0x55/0xb0
>>>
>>> The first HT sibling is waiting for the second in the LP-application
>>> context while the second waits for the first in the scheduler context.
>>>
>>> Any suggestions on how to improve this situation are welcome.
>>
>> Can you test the attached patch, please? It is only tested to boot, so
>> I did no livepatch tests with it.
>
> Thank you for the patch! It seems to fix the issue in my manual testing.
> I'm going to submit automatic LP testing for both thread/core modes.
Andrew suggested to test late ucode loading as well and so I did.
It uses stop_machine() to rendezvous cpus and it failed with a similar
backtrace for a problematic CPU. But in this case the system crashed
since there is no timeout involved:
(XEN) [ 155.025168] Xen call trace:
(XEN) [ 155.040095] [<ffff82d0802417f2>] R _spin_unlock_irq+0x22/0x30
(XEN) [ 155.069549] [<ffff82d08023f3c2>] S
common/schedule.c#sched_wait_rendezvous_in+0xa2/0x270
(XEN) [ 155.109696] [<ffff82d08023f728>] F
common/schedule.c#sched_slave+0x198/0x260
(XEN) [ 155.145521] [<ffff82d080240e1a>] F
common/softirq.c#__do_softirq+0x5a/0x90
(XEN) [ 155.180223] [<ffff82d0803716f6>] F
x86_64/entry.S#process_softirqs+0x6/0x20
It looks like your patch provides a workaround for LP case, but other
cases like stop_machine() remain broken since the underlying issue with
the scheduler is still there.
--
Thanks,
Sergey
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