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SubjectRe: problem with function_graph self-test?

On Thu, 18 Jun 2009, Jeremy Fitzhardinge wrote:
> >
> > This is something that gcc is screwing with us. After spending all day
> > today trying to figure out what is happening, I finally found it in the
> > assembly.
> >
> > In the timer_stats_update_stats function, I get this at the beginning:
> >
> > 00000327 <timer_stats_update_stats>:
> > 327: 57 push %edi
> > 328: 8d 7c 24 08 lea 0x8(%esp),%edi
> > 32c: 83 e4 e0 and $0xffffffe0,%esp
> > 32f: ff 77 fc pushl 0xfffffffc(%edi)
> > 332: 55 push %ebp
> > 333: 89 e5 mov %esp,%ebp
> > 335: 57 push %edi
> > 336: 56 push %esi
> > 337: 53 push %ebx
> > 338: 81 ec 8c 00 00 00 sub $0x8c,%esp
> > 33e: e8 fc ff ff ff call 33f <timer_stats_update_stats+0x18>
> > 33f: R_386_PC32 mcount
> >
> >
> > And this at the end of the function:
> >
> > 4f6: 8d 67 f8 lea 0xfffffff8(%edi),%esp
> > 4f9: 5f pop %edi
> > 4fa: c3 ret
> >
>
> Something to do with using _RET_IP_ in spin_unlock_irqrestore() perhaps?

No, it was the fact that there was a local variable of type struct entry,
where entry was defined to be ____cacheline_aligned_in_smp. But that was
not the end of it. It happens throughout the code. The next hit was in
tcp_ack(). But it has something to do with -Os on i386.
-- Steve



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