Re: [Xen-devel] [for-4.8 PATCH v2] xen: credit2: fix wrong assert in runq_tickle().

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Nov 22, 2016 at 01:51:02PM +0100, Dario Faggioli wrote:
> Since b047f888d489 ("xen: sched: leave CPUs doing tasklet
> work alone") a cpu executing a tasklet, is not marked as
> idle.
> 
> Therefore:
>  - avoid asserting that we can't find the idle vcpu running
>    on one of them, which is not true,
>  - avoid triggering a preemption on them (and add an assert
>    checking that).
> 
> This fixes a bug identified by OSSTest, in flight 102372
> (on ARM, but it's not at all ARM specific), where the
> ASSERT() was triggering like this:
> 
> (XEN) Xen call trace:
> (XEN)    [<0022af78>] sched_credit2.c#runq_tickle+0x3e8/0x61c (PC)
> (XEN)    [<0022aedc>] sched_credit2.c#runq_tickle+0x34c/0x61c (LR)
> (XEN)    [<0022b644>] sched_credit2.c#csched2_context_saved+0x128/0x1a4
> (XEN)    [<0023303c>] context_saved+0x7c/0xa4
> (XEN)    [<0024f660>] domain.c#schedule_tail+0x2b4/0x308
> (XEN)    [<0024faac>] context_switch+0x80/0x94
> (XEN)    [<0022ff48>] schedule.c#schedule+0x76c/0x7ec
> (XEN)    [<002338d4>] softirq.c#__do_softirq+0xcc/0xec
> (XEN)    [<00233968>] do_softirq+0x18/0x28
> (XEN)    [<00261084>] leave_hypervisor_tail+0x58/0x88
> (XEN)    [<002649d0>] entry.o#return_to_guest+0xc/0xb8
> (XEN)
> (XEN) ****************************************
> (XEN) Panic on CPU 1:
> (XEN) Assertion '!is_idle_vcpu(cur->vcpu)' failed at sched_credit2.c:1009
> (XEN) ****************************************
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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