Messages in this thread | | | Subject | Re: [PATCH] perf record: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set | From | "Jin, Yao" <> | Date | Fri, 7 Aug 2020 14:26:35 +0800 |
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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 >> >
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