Re: [RFC patch] use thread.on_ustack to determine if on user stack

Luming Yu
2007-10-16T01:14:49Z

I was thinking the fsys_bubble_down is used to fall back to normal
system call entry if that don't have a ligtweight handler.
Is it right.

On 10/16/07, Fenghua Yu <fenghua.yu@intel.com> wrote:
> On Mon, Oct 15, 2007 at 12:28:05PM +0800, Luming Yu wrote:
> > So my problem is I don't know if it is true that pUStk =
> > thread.on_ustack in fsys mode. And I didn't locate the code that the
> > thread.on_ustack is cleared to 0 during fsys mode.
> > So please help.
>
> In fsys call, pUStk is never equal to thread.on_ustack. Here is the code in
> fsys_bubble_down() in fsys.S.
>
> ....
> st1 [r16]=r0 // M2|3 clear current->thread.on_ustack flag
> ....
> cmp.ne pKStk,pUStk=r0,r0 // A set pKStk <- 0, pUStk <- 1
> ....
>
> The code shows that thread.on_ustack=0 and pUStk=1 during fsys setup phase. The
> two should be equal in other cases than fsys. Seems the two similar names cause
> confusion.
>
> Thanks.
>
> -Fenghua
>