Re: [Xen-devel] [PATCH 3/3] xen/events: schedule if the interrupted task is in a preemptible hypercall

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.02.14 at 20:19, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -1254,6 +1254,12 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
>  
>       irq_exit();
>       set_irq_regs(old_regs);
> +
> +#ifndef CONFIG_PREEMPT
> +     if ( __this_cpu_read(xed_nesting_count) == 0
> +          && is_preemptible_hypercall(regs) )
> +             _cond_resched();
> +#endif

I don't think this can be done here - a 64-bit x86 kernel would
generally be on the IRQ stack, and I don't think scheduling
should be done in this state.

Jan


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