Re: perf top segfaults on current git

[Markus Trippelsdorf <markus@trippelsdorf.de>]

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@redhat.com>
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@intel.com>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Wang Nan <wangnan0@huawei.com>
    Link: http://lkml.kernel.org/n/tip-1pc2v63iphtifovw3bv0bo1v@git.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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

-- 
Markus