Re: [PATCH 2/3] perf_events: fix validation of events using an extra reg (v4)

[Peter Zijlstra <peterz@infradead.org>]

On Mon, 2011-06-06 at 16:57 +0200, Stephane Eranian wrote:
> +static struct cpu_hw_events *allocate_fake_cpuc(void)
> +{
> +       struct cpu_hw_events *cpuc;
> +       int cpu = smp_processor_id();

That's a boo-boo, clearly we are in a preemptible context here (see the
GFP_KERNEL allocation on the next line), so using smp_processor_id()
isn't valid.

Now since all that allocate_shared_regs() does with it is pick a NUMA
node, we should probably use raw_smp_processor_id() and leave it at
that, right?

> +       cpuc = kzalloc(sizeof(*cpuc), GFP_KERNEL);
> +       if (!cpuc)
> +               return ERR_PTR(-ENOMEM);
> +
> +       /* only needed, if we have extra_regs */
> +       if (x86_pmu.extra_regs) {
> +               cpuc->shared_regs = allocate_shared_regs(cpu);
> +               if (!cpuc->shared_regs)
> +                       goto error;
> +       }
> +       return cpuc;
> +error:
> +       free_fake_cpuc(cpuc);
> +       return ERR_PTR(-ENOMEM);
> +}