Em Fri, Aug 07, 2020 at 09:16:29AM -0300, Arnaldo Carvalho de Melo escreveu: > Em Fri, Aug 07, 2020 at 09:09:56AM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Fri, Aug 07, 2020 at 09:08:24AM -0300, Arnaldo Carvalho de Melo escreveu: > > > 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. > > > > I backtrack on that, as the sideband event is not just for BPF... The > > switch-output-event code uses it as well, so it can't be dependent on > > LIBBPF being built... > > > > I'll see what I can do > > So this is the change I made, the side band thread is may have been > already created by > > [acme@quaco ~]$ perf record -h switch-output-event > > Usage: perf record [<options>] [<command>] > or: perf record [<options>] -- <command> [<options>] > > --switch-output-event <switch output event> > switch output event selector. use 'perf list' to > list available events > > [acme@quaco ~]$ > > I'm doing some extra checking now on your report, and the patch below > has skews because it clashed with the clockid patches by Jiri so I had > to resolve its merge. Sorry, I resent your patch, doh, here is the end result, with my change, its ok to call perf_evlist__start_sb_thread() with a NULL evlist, it'll just return 0.
- Arnald commit b13536a7e93680625094beb18cdce4ae47a3dbfb Author: Jin Yao <yao....@linux.intel.com> Date: Wed Aug 5 10:29:37 2020 +0800 perf record: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set 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 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. Committer notes: The side band thread is not used just with BPF, it is also used with --switch-output-event, so narrow the ifdef to the BPF specific part. Fixes: 23cbb41c939a ("perf record: Move side band evlist setup to separate routine") Signed-off-by: Jin Yao <yao....@linux.intel.com> Acked-by: Jiri Olsa <jo...@kernel.org> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com> Cc: Andi Kleen <a...@linux.intel.com> Cc: Jin Yao <yao....@intel.com> Cc: Kan Liang <kan.li...@linux.intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Link: http://lore.kernel.org/lkml/20200805022937.29184-1-yao....@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 7d97c8e9f7f9..f91352f847c0 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1531,7 +1531,7 @@ static int record__setup_sb_evlist(struct record *rec) evlist__set_cb(rec->sb_evlist, record__process_signal_event, rec); rec->thread_id = pthread_self(); } - +#ifdef HAVE_LIBBPF_SUPPORT if (!opts->no_bpf_event) { if (rec->sb_evlist == NULL) { rec->sb_evlist = evlist__new(); @@ -1547,7 +1547,7 @@ static int record__setup_sb_evlist(struct record *rec) return -1; } } - +#endif if (perf_evlist__start_sb_thread(rec->sb_evlist, &rec->opts.target)) { pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n"); opts->no_bpf_event = true;