Re: perf top segfaults on current git
From: Jiri Olsa
Date: Wed Nov 04 2015 - 07:27:49 EST
On Wed, Nov 04, 2015 at 11:49:30AM +0100, Markus Trippelsdorf wrote:
> On 2015.11.04 at 11:15 +0100, Markus Trippelsdorf wrote:
> > On 2015.11.03 at 11:02 +0100, Ingo Molnar wrote:
> > >
> > > Please pull the latest perf-core-for-linus git tree from:
> >
> > Since the current merge "perf top" segfaults on my machine:
> >
> > Program received signal SIGSEGV, Segmentation fault.
> >
> > __map__is_kernel (map=map@entry=0x1abb7a0) at util/map.c:238
> > 238 return __machine__kernel_map(map->groups->machine, map->type) == map;
> > (gdb) bt
> > #0 __map__is_kernel (map=map@entry=0x1abb7a0) at util/map.c:238
> > #1 0x00000000004393e4 in symbol_filter (map=map@entry=0x1abb7a0, sym=sym@entry=0x1a88560) at builtin-top.c:658
> > #2 0x00000000004fcd4d in dso__load_sym (dso=dso@entry=0x166dae0, map=map@entry=0x1abb7a0, syms_ss=0x7fffffff7680, runtime_ss=runtime_ss@entry=0x7fffffff7680,
> > filter=filter@entry=0x4393c0 <symbol_filter>, kmodule=0) at util/symbol-elf.c:1082
> > #3 0x00000000004a64e0 in dso__load (dso=0x166dae0, map=map@entry=0x1abb7a0, filter=filter@entry=0x4393c0 <symbol_filter>) at util/symbol.c:1530
> > #4 0x00000000004b941f in map__load (filter=0x4393c0 <symbol_filter>, map=<optimized out>) at util/map.c:289
> > #5 map__find_symbol (map=0x1abb7a0, addr=40188, filter=0x4393c0 <symbol_filter>) at util/map.c:333
> > #6 0x00000000004803b1 in perf_event__preprocess_sample (event=event@entry=0x7ffff6a7a5f0, machine=machine@entry=0x164c7b8, al=al@entry=0x7fffffff8a90,
> > sample=sample@entry=0x7fffffff8b20) at util/event.c:1045
> > #7 0x0000000000439837 in perf_event__process_sample (machine=0x164c7b8, sample=0x7fffffff8b20, evsel=0x164c320, event=0x7ffff6a7a5f0, tool=0x7fffffff8ef0)
> > at builtin-top.c:737
> > #8 perf_top__mmap_read_idx (top=top@entry=0x7fffffff8ef0, idx=idx@entry=0) at builtin-top.c:870
> > #9 0x000000000043b9ef in perf_top__mmap_read (top=0x7fffffff8ef0) at builtin-top.c:887
> > #10 __cmd_top (top=0x7fffffff8ef0) at builtin-top.c:1000
> > #11 cmd_top (argc=<optimized out>, argv=<optimized out>, prefix=<optimized out>) at builtin-top.c:1329
> > #12 0x00000000004756b3 in run_builtin (p=p@entry=0x5b0608 <commands+264>, argc=argc@entry=2, argv=argv@entry=0x7fffffffe500) at perf.c:386
> > #13 0x00000000004203e2 in handle_internal_command (argv=0x7fffffffe500, argc=2) at perf.c:447
> > #14 run_argv (argv=0x7fffffffe290, argcp=0x7fffffffe29c) at perf.c:491
> > #15 main (argc=2, argv=0x7fffffffe500) at perf.c:608
> >
> > It only happens occasionally (~every third or fourth run).
>
> Apparently it started with:
>
> commit cfc5acd4c80b875d2f739d6a93562034aee5563f
> Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Date: Wed Sep 23 15:15:54 2015 -0300
>
> perf top: Filter symbols based on __map__is_kernel(map)
>
> Instead of using dso->kernel, this is equivalent at the moment,
> and helps in reducing the accesses to dso->kernel.
>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Stephane Eranian <eranian@xxxxxxxxxx>
> Cc: Wang Nan <wangnan0@xxxxxxxxxx>
> Link: http://lkml.kernel.org/n/tip-1pc2v63iphtifovw3bv0bo1v@xxxxxxxxxxxxxx
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index bdaf44f24d5d..38d4d6cac823 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -655,7 +655,7 @@ static int symbol_filter(struct map *map, struct symbol *sym)
> {
> const char *name = sym->name;
>
> - if (!map->dso->kernel)
> + if (!__map__is_kernel(map))
> return 0;
> /*
> * ppc64 uses function descriptors and appends a '.' to the
>
I think it's correct to assume map->groups != NULL,
IMO the change just uncovered another bug
I couldn't reproduce this, but I could find one place where this
assumption is broken.. could you please try attached patch?
thanks,
jirka
---
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 4e38c396a897..afc6b56cf749 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -644,6 +644,12 @@ size_t map_groups__fprintf(struct map_groups *mg, FILE *fp)
return printed;
}
+static void __map_groups__insert(struct map_groups *mg, struct map *map)
+{
+ __maps__insert(&mg->maps[map->type], map);
+ map->groups = mg;
+}
+
static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp)
{
struct rb_root *root;
@@ -682,7 +688,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
}
before->end = map->start;
- __maps__insert(maps, before);
+ __map_groups__insert(pos->groups, before);
if (verbose >= 2)
map__fprintf(before, fp);
}
@@ -696,7 +702,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
}
after->start = map->end;
- __maps__insert(maps, after);
+ __map_groups__insert(pos->groups, after);
if (verbose >= 2)
map__fprintf(after, fp);
}
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