Re: [PATCH] i386-pda UP optimization

[Eric Dumazet <dada1@cosmosbay.com>]

On Wednesday 15 November 2006 18:49, Ingo Molnar wrote:
> * Eric Dumazet <dada1@cosmosbay.com> wrote:
> > Machine boots but freeze when init starts. Any idea ?
>
> probably caused by this:
> > +# define GET_CPU_NUM(reg)
> >
> >  #define FIXUP_ESPFIX_STACK \
> >  	/* since we are on a wrong stack, we cant make it a C code :( */ \
> > -	movl %gs:PDA_cpu, %ebx; \
> > +	GET_CPU_NUM(%ebx) \
> >  	PER_CPU(cpu_gdt_descr, %ebx); \
> >  	movl GDS_address(%ebx), %ebx; \
>
> %ebx very definitely wants to have a current CPU number loaded ;) Pick
> it up from the task struct.

Hum.... Are you sure ?

For UP we have this PER_CPU definition :

#define PER_CPU(var, cpu) \
        movl $per_cpu__/**/var, cpu;

You can see 'cpu' is a pure output , not an input value.

So I basically deleted the fist instruction of this sequence :

movl %gs:PDA_cpu, %ebx
movl $per_cpu__cpu_gdt_descr, %ebx;

Did I miss something ?