Re: [PATCH 01/10] perf, trace: Remove IRQ-disable from perf/tracepoint interaction

Frederic Weisbecker
2010-05-24T11:31:16Z

On Sun, May 23, 2010 at 08:16:27PM +0200, Peter Zijlstra wrote:
> On Sun, 2010-05-23 at 22:11 +1000, Paul Mackerras wrote:
> > On Fri, May 21, 2010 at 11:02:02AM +0200, Peter Zijlstra wrote:
> >
> > > entry = (struct trace_entry *)raw_data;
> > > - tracing_generic_entry_update(entry, *irq_flags, pc);
> > > + tracing_generic_entry_update(entry, regs->flags, pc);
> > > entry->type = type;
> >
> > This is breaking on powerpc -- we don't have a "flags" element in
> > struct pt_regs. What is it trying to do? Get the interrupt enable
> > state, as local_irq_save(flags) would provide?
>
> Yes, I fouled that up.
>
> On x86 perf_arch_fetch_caller_regs() stores pt_regs::flags, which is the
> same as used in local_save_flags().
>
> So to avoid another local_save_flags() for the ftrace code, I wanted to
> reuse it, and totally forgot the !x86 side of things.
>
> Possibly we could remove the local_save_flags() from the
> perf_arch_fetch_caller_regs() as I'm not sure we actually use
> pt_regs::flags (Frederic?) and leave the ftrace thing to use
> local_save_flags().

It was an anticipation for further uses. But since further are not
appearing, you can safely remove it.

Thanks.