On Tue, May 31, 2016 at 11:19:11AM +0000, He Kuang wrote: SNIP
> diff --git a/tools/perf/util/unwind-libunwind.c > b/tools/perf/util/unwind-libunwind.c > index e183390..5774317 100644 > --- a/tools/perf/util/unwind-libunwind.c > +++ b/tools/perf/util/unwind-libunwind.c > @@ -5,6 +5,7 @@ > #include "arch/common.h" > > struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops; > +struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops; > > void unwind__register_ops(struct thread *thread, > struct unwind_libunwind_ops *ops) > @@ -30,7 +31,13 @@ int unwind__prepare_access(struct thread *thread, struct > map *map) > dso_type == DSO__TYPE_64BIT, map->dso->name); > > arch = normalize_arch(thread->mg->machine->env->arch); > - pr_debug("unwind: target platform=%s\n", arch); > + > + if (!strcmp(arch, "x86")) > + if (dso_type != DSO__TYPE_64BIT) > + ops = x86_32_unwind_libunwind_ops; > + > + if (!ops) > + pr_err("unwind: target platform=%s is not supported\n", arch); how could ops become NULL in here? it starts with local_unwind_libunwind_ops I dont think this check is needed in here jirka