Em Thu, Aug 06, 2020 at 09:43:57PM +0200, Jiri Olsa escreveu:
> On Wed, Aug 05, 2020 at 10:29:37AM +0800, Jin Yao wrote:
> > We received an error report that perf-record caused 'Segmentation fault'
> > on a newly system (e.g. on the new installed ubuntu).
> >
> > (gdb) backtrace
> > #0 __read_once_size (size=4, res=<synthetic pointer>, p=0x14) at
> > /root/0-jinyao/acme/tools/include/linux/compiler.h:139
> > #1 atomic_read (v=0x14) at
> > /root/0-jinyao/acme/tools/include/asm/../../arch/x86/include/asm/atomic.h:28
> > #2 refcount_read (r=0x14) at
> > /root/0-jinyao/acme/tools/include/linux/refcount.h:65
> > #3 perf_mmap__read_init (map=map@entry=0x0) at mmap.c:177
> > #4 0x0000561ce5c0de39 in perf_evlist__poll_thread (arg=0x561ce68584d0) at
> > util/sideband_evlist.c:62
> > #5 0x00007fad78491609 in start_thread (arg=<optimized out>) at
> > pthread_create.c:477
> > #6 0x00007fad7823c103 in clone () at
> > ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
>
> hum, I recall discussing the same issue,
> I thought it was already fixed :-\ in any case:
>
> Acked-by: Jiri Olsa <jo...@redhat.com>
I added this:
Fixes: 23cbb41c939a ("perf record: Move side band evlist setup to separate
routine")
To help this fixe go back to a few stable kernels. Technically the
problem was introduced much earlier, when the side band thread was
added, but then this would require more cherry-picking of patches and
since we have a workaround, i.e. build with libbpf, I think this is
enough.
Applied,
- Arnaldo
> thanks,
> jirka
>
> >
> > The root cause is, evlist__add_bpf_sb_event() just returns 0 if
> > HAVE_LIBBPF_SUPPORT is not defined (inline function path). So it will
> > not create a valid evsel for side-band event.
> >
> > But perf-record still creates BPF side band thread to process the
> > side-band event, then the error happpens.
> >
> > We can reproduce this issue by removing the libelf-dev. e.g.
> > 1. apt-get remove libelf-dev
> > 2. perf record -a -- sleep 1
> >
> > root@test:~# ./perf record -a -- sleep 1
> > perf: Segmentation fault
> > Obtained 6 stack frames.
> > ./perf(+0x28eee8) [0x5562d6ef6ee8]
> > /lib/x86_64-linux-gnu/libc.so.6(+0x46210) [0x7fbfdc65f210]
> > ./perf(+0x342e74) [0x5562d6faae74]
> > ./perf(+0x257e39) [0x5562d6ebfe39]
> > /lib/x86_64-linux-gnu/libpthread.so.0(+0x9609) [0x7fbfdc990609]
> > /lib/x86_64-linux-gnu/libc.so.6(clone+0x43) [0x7fbfdc73b103]
> > Segmentation fault (core dumped)
> >
> > To fix this issue,
> >
> > 1. We either install the missing libraries to let HAVE_LIBBPF_SUPPORT
> > be defined.
> > e.g. apt-get install libelf-dev and install other related libraries.
> >
> > 2. Use this patch to skip the side-band event setup if HAVE_LIBBPF_SUPPORT
> > is not set.
> >
> > Signed-off-by: Jin Yao <yao....@linux.intel.com>
> > ---
> > tools/perf/builtin-record.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index b6bdccd875bc..ae97f98e2753 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -1506,6 +1506,7 @@ static int record__synthesize(struct record *rec,
> > bool tail)
> > return err;
> > }
> >
> > +#ifdef HAVE_LIBBPF_SUPPORT
> > static int record__process_signal_event(union perf_event *event
> > __maybe_unused, void *data)
> > {
> > struct record *rec = data;
> > @@ -1550,6 +1551,12 @@ static int record__setup_sb_evlist(struct record
> > *rec)
> >
> > return 0;
> > }
> > +#else
> > +static int record__setup_sb_evlist(struct record *rec __maybe_unused)
> > +{
> > + return 0;
> > +}
> > +#endif
> >
> > static int __cmd_record(struct record *rec, int argc, const char **argv)
> > {
> > --
> > 2.17.1
> >
>
--
- Arnaldo
