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 | Mon, 10 Aug 2020 08:35:00 +0800 |
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Hi Arnaldo,
On 8/7/2020 8:28 PM, Arnaldo Carvalho de Melo wrote: > 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 <jolsa@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.jin@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.jin@linux.intel.com> > Acked-by: Jiri Olsa <jolsa@kernel.org> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> > Cc: Andi Kleen <ak@linux.intel.com> > Cc: Jin Yao <yao.jin@intel.com> > Cc: Kan Liang <kan.liang@linux.intel.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Link: http://lore.kernel.org/lkml/20200805022937.29184-1-yao.jin@linux.intel.com > Signed-off-by: Arnaldo Carvalho de Melo <acme@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; >
Thanks so much for helping to refine the patch!
Thanks Jin Yao
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