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

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 12/02/14 11:59, Jan Beulich wrote:
>>>> 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.

_cond_resched() doesn't look that different from preempt_schedule_irq()
which is explicitly callable from irq context.

David

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel