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 <jo...@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....@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
