lkml.org 
[lkml]   [2020]   [Aug]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] perf record: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set
From
Date
Hi Jiri,

On 8/7/2020 3:43 AM, Jiri Olsa wrote:
> 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:
>

Is it possible some patches have been posted but we missed? :)

> Acked-by: Jiri Olsa <jolsa@redhat.com>
>

Thanks!

Thanks
Jin Yao

> 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.jin@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
>>
>

\
 
 \ /
  Last update: 2020-08-07 08:26    [W:0.718 / U:0.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site