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SubjectRe: [PATCH 05/48] percpu: Add preemption checks to __this_cpu ops
On Tue, 4 Mar 2014 14:27:27 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 14 Feb 2014 14:18:46 -0600 Christoph Lameter <cl@linux.com> wrote:
>
> > [Patch depends on another patch in this series that introduces raw_cpu_ops]
> >
> > We define a check function in order to avoid trouble with the
> > include files. Then the higher level __this_cpu macros are
> > modified to invoke the preemption check.
> >
> > --- linux.orig/lib/smp_processor_id.c 2014-01-30 14:40:50.936519233 -0600
> > +++ linux/lib/smp_processor_id.c 2014-01-30 14:40:50.936519233 -0600
> > @@ -7,7 +7,7 @@
> > #include <linux/kallsyms.h>
> > #include <linux/sched.h>
> >
> > -notrace unsigned int debug_smp_processor_id(void)
> > +notrace static unsigned int check_preemption_disabled(char *what)
> > {
> > int this_cpu = raw_smp_processor_id();
> >
> > @@ -38,9 +38,9 @@
> > if (!printk_ratelimit())
> > goto out_enable;
> >
> > - printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
> > - "code: %s/%d\n",
> > - preempt_count() - 1, current->comm, current->pid);
> > + printk(KERN_ERR "BUG: using %s in preemptible [%08x] code: %s/%d\n",
> > + what, preempt_count() - 1, current->comm, current->pid);
> > +
> > print_symbol("caller is %s\n", (long)__builtin_return_address(0));
> > dump_stack();
>
> I wonder if there's any point in printing __builtin_return_address.
> Doesn't dump_stack() tell us the same thing?

When frame pointers are enabled, sure. But without frame pointers, I'm
not so sure.

-- Steve


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