Re: [patch 02/2] allow gcc4 to optimize unit-at-a-time

[Andreas Kleen <ak@suse.de>]

Am Mi 28.12.2005 16:41 schrieb Ingo Molnar <mingo@elte.hu>:

>
> * Andi Kleen <ak@suse.de> wrote:
>
> > But one caveat: turning on unit-at-a-time makes objdump -S / make
> > foo/bar.lst with CONFIG_DEBUG_INFO essentially useless because
> > objdump
> > cannot deal with functions being out of order in the object file.
> > This
> > can be a big problem while analyzing oopses - essentially you have
> > to
> > analyze the functions without source level information. And with
> > unit-at-a-time they become bigger so it's more difficult.
> >
> > But I still think it's a good idea.
>
> hm, i dont seem to have problems with DEBUG_INFO. I picked a random
> address within the kernel:
>
> c035766f T schedule_timeout
>
> (gdb) list *0xc035768f
> 0xc035768f is in schedule_timeout (kernel/timer.c:1075).
> 1070 * should never happens anyway). You just have the printk()
> 1071 * that will tell you if something is gone wrong and where.
> 1072 */
> 1073 if (timeout < 0)
> 1074 {
> 1075 printk(KERN_ERR "schedule_timeout: wrong timeout "
> 1076 "value %lx from %p
", timeout,
> 1077 __builtin_return_address(0));
> 1078 current->state = TASK_RUNNING;
> 1079 goto out;
> (gdb)
>
> or is it something else that breaks?

It's objdump that breaks. Try objdump -S. gdb can deal with it, but you
can't generate
mixed C/assembly listings with it, so it's hard to match up the exact
lines.

(apparently it's possible through the gdb/mi interface, but I haven't
attempted
that yet)

-Andi