Re: [Patch 2 of 2]: PV-domain SMP performance Linux-part

[Juergen Gross <juergen.gross@fujitsu-siemens.com>]

Jan Beulich wrote:
>> --- a/include/asm-x86_64/mach-xen/asm/irqflags.h	Sat Dec 13 16:00:43 2008 +0000
>> +++ b/include/asm-x86_64/mach-xen/asm/irqflags.h	Wed Dec 17 13:12:53 2008 +0100
>> @@ -33,8 +33,12 @@ do {									\
>> 	vcpu_info_t *_vcpu;						\
>> 	barrier();							\
>> 	_vcpu = current_vcpu_info();		\
>> -	if ((_vcpu->evtchn_upcall_mask = (x)) == 0) {			\
>> +	if ( !(x) ) {							\
> 
> This isn't correct, as it breaks 0->1 transitions (there are a few instances of
> this in the kernel).

Thanks!
I will correct it.

> 
>> +		_vcpu->no_desched = 0;					\
>> +	        _vcpu->evtchn_upcall_mask = 0;				\
>> 		barrier(); /* unmask then check (avoid races) */	\
>> +		if ( unlikely(_vcpu->desched_delay) )			\
>> +			(void)((HYPERVISOR_sched_op(SCHEDOP_yield, _vcpu))?:0); \
> 
> Why not just cast the function result to void? Likewise further below...

I took that from include/xen/hypercall.h, which mentioned problems with just
casting the function result.


Juergen

-- 
Juergen Gross                             Principal Developer
IP SW OS6                      Telephone: +49 (0) 89 636 47950
Fujitsu Siemens Computers         e-mail: juergen.gross@fujitsu-siemens.com
Otto-Hahn-Ring 6                Internet: www.fujitsu-siemens.com
D-81739 Muenchen         Company details: www.fujitsu-siemens.com/imprint.html