Date: Thu, 5 Nov 2020 16:01:00 -0800 From: Patrick Mahan <plmahan@gmail.com> To: Pete Wright <pete@nomadlogic.org> Cc: questions list <freebsd-questions@freebsd.org> Subject: Re: Helping understand cause of SIGSEGV Message-ID: <CAFDHx1Jg_9k3oWU8X-WdP2CJX8hnBYgMz%2BvxwOs766JZcM3WRQ@mail.gmail.com> In-Reply-To: <c2eab4b0-b10b-9db3-1aa3-1f61689e24e8@nomadlogic.org> References: <c2eab4b0-b10b-9db3-1aa3-1f61689e24e8@nomadlogic.org>
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On Thu, Nov 5, 2020 at 10:20 AM Pete Wright <pete@nomadlogic.org> wrote: > i was hoping someone with more experience in C and threading can help me > better understand this SIGSEGV fault I'm hitting. the background is I'm > trying to get sysutils/fluent-bit working on 12.2-RELEASE as well as on > CURRENT. > > I've created the following PR and upstream github issues: > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=250825 > https://github.com/fluent/fluent-bit/issues/2747 > > so where i am at now is i am able to generate a useful core file when it > hits the fault and can step through it in lldb. > > here is the output from fluent-bit: > |[2020/11/04 22:18:12] [debug] [task] created task=0x416410a0 id=0 OK > [2020/11/04 22:18:12] [trace] [thread 0x416091c0] created (custom data > at 0x416091e0, size=80 > [2020/11/04 22:18:12] [engine] caught signal (SIGSEGV) > #0 0x406d11ee in thr_sighandler() at > /lib/libthr/thread/thr_sig.c:246 > Abort trap (core dumped)| > > > here's an example from one of the threads (the github link above has the > full backtrace) from lldb: > > | thread #1, name = 'fluent-bit', stop reason = signal SIGABRT > * frame #0: 0x000000004087100a libc.so.7`__sys_thr_kill at thr_kill.S:4 > frame #1: 0x00000000407e6c84 libc.so.7`__raise(s=6) at raise.c:52:10 > frame #2: 0x000000004089a5d9 libc.so.7`abort at abort.c:67:8 > frame #3: 0x000000000034a7a8 > fluent-bit`flb_signal_handler(signal=11) at fluent-bit.c:418:9 > frame #4: 0x00000000406d1c20 > libthr.so.3`handle_signal(actp=0x00007fffdfffc600, sig=11, > info=0x00007fffdfffc9f0, ucp=0x00007fffdfffc680) at thr_sig.c:303:3 > frame #5: 0x00000000406d11ef libthr.so.3`thr_sighandler(sig=11, > info=0x00007fffdfffc9f0, _ucp=0x00007fffdfffc680) at thr_sig.c:246:2 > frame #6: 0x00007fffffffe193 > frame #7: 0x000000000036fe0c fluent-bit`tasks_start [inlined] > output_params_set(th=0x00000000416091c0, data=0x000000004165d980, > bytes=128, tag="random.0", tag_len=8, i_ins=0x0000000040e58000, > out_plugin=0x0000000040e2dfc0, out_context=0x00000000416051e0, > config=0x0000000040e19180) at flb_output.h:429:5 > I would look at what is happening here in output_params_set(). Something is accessing out of bounds memory. > frame #8: 0x000000000036fd14 fluent-bit`tasks_start [inlined] > flb_output_thread(task=0x00000000416410a0, i_ins=0x0000000040e58000, > o_ins=0x0000000040e5b000, config=0x0000000040e19180, > buf=0x000000004165d980, size=128, tag="random.0", tag_len=8) at > flb_output.h:522 > frame #9: 0x000000000036fab5 > fluent-bit`tasks_start(in=0x0000000040e58000, config=0x0000000040e19180) > at flb_engine_dispatch.c:190 > frame #10: 0x000000000036f6fd fluent-bit`flb_engine_dispatch(id=0, > in=0x0000000040e58000, config=0x0000000040e19180) at > flb_engine_dispatch.c:293:5 > frame #11: 0x000000000036ce10 > fluent-bit`flb_engine_flush(config=0x0000000040e19180, > in_force=0x0000000000000000) at flb_engine.c:85:9 > frame #12: 0x000000000036d43a fluent-bit`flb_engine_start [inlined] > flb_engine_handle_event(fd=20, mask=1, config=0x0000000040e19180) at > flb_engine.c:292:13 > frame #13: 0x000000000036d3e6 > fluent-bit`flb_engine_start(config=0x0000000040e19180) at flb_engine.c:559 > frame #14: 0x00000000003564ec > fluent-bit`flb_lib_worker(data=0x0000000040e19180) at flb_lib.c:488:11 > frame #15: 0x00000000406c87db > libthr.so.3`thread_start(curthread=0x0000000040e12500) at > thr_create.c:292:16 > > Patrick
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