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AJvYcCU59BTQEREqulykLOKW1cAAmkusVCzoxfMy3C1FGg+JWkpiDojUhMntSrFyEjxKjJFhJwgMMmGrV1jDqtkBFoUM@vger.kernel.org X-Gm-Message-State: AOJu0Yy/acGs3yLQYrM/7BisOOtbt1MijQBC2cfFiWy2qd5yv+KblXUK rN/Tf+FN8sys2Zw4kPQTTvR18npRsd67/nHF92ovF+NBCZOejYRTEAGxC4GU9Ot3xHxFDqoDgFM hyKinVMu80G/W7d6LaX1bwEKIyE8GJAYQtgC4LKK/ X-Gm-Gg: ASbGncsB4HEYzxWkzRpRbpXDKfFC5JZfeDzjusHWheLSOWlp5VoUlyHSg9vVc8pyzpE FfWxaje99m9PUB2zskc2KWm9FflhrV7wU2joWN2PHo3oGusn6COFoSjdlNZ89aV/Zi10WcAdEWN 4lgmQwVqLdnXrcuN7kvLvl1ZN3XMcCVmVMOZ4x3MrECFYk6Xcj9p5ENGZkdqo+mviAprFqqdia X-Google-Smtp-Source: AGHT+IGcgjDveA1f2goly7nIa337NOCnuv1+3aIFsV9PYdV/9Phe1S4XNa8ammEYnRO2Px1DffFAov8T3xUobdN1Hws= X-Received: by 2002:a05:6e02:156b:b0:3dd:a524:9470 with SMTP id e9e14a558f8ab-3dda5249625mr5135335ab.27.1748885546614; Mon, 02 Jun 2025 10:32:26 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250529052322.381947-1-irogers@google.com> <20250529052322.381947-2-irogers@google.com> In-Reply-To: From: Ian Rogers Date: Mon, 2 Jun 2025 10:32:15 -0700 X-Gm-Features: AX0GCFtvM9h-svrhY-U-soiP0u8TEbc_-RHxISmm1FBYq42MREbKbhJ53qT0dXU Message-ID: Subject: Re: [PATCH v2 2/2] perf debug: Add function symbols to dump_stack To: Arnaldo Carvalho de Melo Cc: Peter Zijlstra , Ingo Molnar , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , James Clark , Howard Chu , Yicong Yang , Michael Petlan , Andi Kleen , Christophe Leroy , "Dr. David Alan Gilbert" , =?UTF-8?Q?Krzysztof_=C5=81opatowski?= , Dmitry Vyukov , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, May 29, 2025 at 3:02=E2=80=AFPM Ian Rogers wro= te: > > On Thu, May 29, 2025 at 1:21=E2=80=AFPM Arnaldo Carvalho de Melo > wrote: > > > > On Wed, May 28, 2025 at 10:23:22PM -0700, Ian Rogers wrote: > > > Symbolize stack traces by creating a live machine. Add this > > > functionality to dump_stack and switch dump_stack users to use > > > it. Switch TUI to use it. Add stack traces to the child test function > > > which can be useful to diagnose blocked code. > > > > > > Example output: > > > ``` > > > 8: PERF_RECORD_* events & perf_sample fields = : Running (1 active) > > > ^C > > > Signal (2) while running tests. > > > Terminating tests with the same signal > > > Internal test harness failure. Completing any started tests: > > > : 8: PERF_RECORD_* events & perf_sample fields: > > > > So you are testing it with: > > > > root@number:~# perf test PERF_RECORD > > 8: PERF_RECORD_* events & perf_sample fields : = Running (1 active) > > ^C > > Signal (2) while running tests. > > Terminating tests with the same signal > > Internal test harness failure. Completing any started tests: > > 8: PERF_RECORD_* events & perf_sample fields : = Skip (permissions) > > root@number:~# > > > > ? > > You are running the test as a child and by default the child test > output is only displayed if verbose is enabled. I use verbose=3D2 below > as verbose=3D1 won't display anything unless the child test gives a fail > exit value: > ``` > $ git log --oneline > b9ac06abfde9 perf debug: Add function symbols to dump_stack > e561806265ed perf machine: Factor creating a "live" machine out of dwarf-= unwind > 628e124404b3 perf tests switch-tracking: Fix timestamp comparison > $ make -C tools/perf O=3D/tmp/perf > ... > $ sudo /tmp/perf/perf test -vv PERF_RECORD > 8: PERF_RECORD_* events & perf_sample fields: > 8: PERF_RECORD_* events & perf_sample fields : > Running (1 active) > ^C > Signal (2) while running tests. > Terminating tests with the same signal > Internal test harness failure. Completing any started tests: > : 8: PERF_RECORD_* events & perf_sample fields: > > ---- unexpected signal (2) ---- > #0 0x5617ec45e5e3 in child_test_sig_handler builtin-test.c:0 > #1 0x7f855c649df0 in __restore_rt libc_sigaction.c:0 > #2 0x7f855c699687 in __internal_syscall_cancel cancellation.c:64 > #3 0x7f855c6e5f7a in clock_nanosleep@GLIBC_2.2.5 clock_nanosleep.c:72 > #4 0x7f855c6f1393 in __nanosleep nanosleep.c:26 > #5 0x7f855c702d68 in __sleep sleep.c:55 > #6 0x5617ec46ebfb in test__PERF_RECORD perf-record.c:0 > #7 0x5617ec45e4f0 in run_test_child builtin-test.c:0 > #8 0x5617ec3faf0d in start_command run-command.c:127 > #9 0x5617ec45f433 in __cmd_test builtin-test.c:0 > #10 0x5617ec45faff in cmd_test perf[147aff] > #11 0x5617ec3ed960 in run_builtin perf.c:0 > #12 0x5617ec3edc7b in handle_internal_command perf.c:0 > #13 0x5617ec368d33 in main perf[50d33] > #14 0x7f855c633ca8 in __libc_start_call_main libc_start_call_main.h:74 > #15 0x7f855c633d65 in __libc_start_main@@GLIBC_2.34 libc-start.c:128 > #16 0x5617ec369381 in _start perf[51381] > > ---- unexpected signal (2) ---- > #0 0x5617ec45e5e3 in child_test_sig_handler builtin-test.c:0 > #1 0x7f855c649df0 in __restore_rt libc_sigaction.c:0 > #2 0x7f855c6a3a14 in pthread_sigmask@GLIBC_2.2.5 pthread_sigmask.c:45 > #3 0x7f855c649fd9 in __GI___sigprocmask sigprocmask.c:26 > #4 0x7f855c72601b in __longjmp_chk longjmp.c:36 > #5 0x5617ec45e600 in print_test_result.isra.0 builtin-test.c:0 > #6 0x7f855c649df0 in __restore_rt libc_sigaction.c:0 > #7 0x7f855c699687 in __internal_syscall_cancel cancellation.c:64 > #8 0x7f855c6e5f7a in clock_nanosleep@GLIBC_2.2.5 clock_nanosleep.c:72 > #9 0x7f855c6f1393 in __nanosleep nanosleep.c:26 > #10 0x7f855c702d68 in __sleep sleep.c:55 > #11 0x5617ec46ebfb in test__PERF_RECORD perf-record.c:0 > #12 0x5617ec45e4f0 in run_test_child builtin-test.c:0 > #13 0x5617ec3faf0d in start_command run-command.c:127 > #14 0x5617ec45f433 in __cmd_test builtin-test.c:0 > #15 0x5617ec45faff in cmd_test perf[147aff] > #16 0x5617ec3ed960 in run_builtin perf.c:0 > #17 0x5617ec3edc7b in handle_internal_command perf.c:0 > #18 0x5617ec368d33 in main perf[50d33] > #19 0x7f855c633ca8 in __libc_start_call_main libc_start_call_main.h:74 > #20 0x7f855c633d65 in __libc_start_main@@GLIBC_2.34 libc-start.c:128 > #21 0x5617ec369381 in _start perf[51381] > 8: PERF_RECORD_* events & perf_sample fields : > Skip (permissions) > ``` > > > > I built it with DEBUG=3D1 and without, and with your patch, following y= our > > example output, I'm not being able to reproduce. > > > > Tried it as well with: > > > > =E2=AC=A2 [acme@toolbx perf-tools-next]$ cat segv.patch > > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c > > index 8b30c6f16a9eeac1..e55d86f1097d6d79 100644 > > --- a/tools/perf/util/symbol.c > > +++ b/tools/perf/util/symbol.c > > @@ -402,6 +402,8 @@ static struct symbol *symbols__find(struct rb_root_= cached *symbols, u64 ip) > > { > > struct rb_node *n; > > > > + *(int *)NULL =3D 0; > > + > > if (symbols =3D=3D NULL) > > return NULL; > > > > =E2=AC=A2 [acme@toolbx perf-tools-next]$ patch -p1 < segv.patch > > patching file tools/perf/util/symbol.c > > =E2=AC=A2 [acme@toolbx perf-tools-next]$ m > > rm: cannot remove '/home/acme/libexec/perf-core/scripts/python/Perf-Tra= ce-Util/lib/Perf/Trace/__pycache__/Core.cpython-313.pyc': Permission denied > > make: Entering directory '/home/acme/git/perf-tools-next/tools/perf' > > BUILD: Doing 'make -j32' parallel build > > Warning: Kernel ABI header differences: > > diff -u tools/arch/arm64/include/asm/cputype.h arch/arm64/include/asm= /cputype.h > > > > Auto-detecting system features: > > ... libdw: [ on ] > > ... glibc: [ on ] > > ... libelf: [ on ] > > ... libnuma: [ on ] > > ... numa_num_possible_cpus: [ on ] > > ... libperl: [ on ] > > ... libpython: [ on ] > > ... libcrypto: [ on ] > > ... libcapstone: [ on ] > > ... llvm-perf: [ on ] > > ... zlib: [ on ] > > ... lzma: [ on ] > > ... get_cpuid: [ on ] > > ... bpf: [ on ] > > ... libaio: [ on ] > > ... libzstd: [ on ] > > > > INSTALL libsubcmd_headers > > INSTALL libperf_headers > > INSTALL libapi_headers > > INSTALL libsymbol_headers > > INSTALL libbpf_headers > > CC /tmp/build/perf-tools-next/util/symbol.o > > LD /tmp/build/perf-tools-next/util/perf-util-in.o > > LD /tmp/build/perf-tools-next/perf-util-in.o > > AR /tmp/build/perf-tools-next/libperf-util.a > > LINK /tmp/build/perf-tools-next/perf > > GEN /tmp/build/perf-tools-next/python/perf.cpython-313-x86_64-lin= ux-gnu.so > > INSTALL binaries > > INSTALL tests > > INSTALL libperf-jvmti.so > > INSTALL libexec > > INSTALL perf-archive > > INSTALL perf-iostat > > INSTALL perl-scripts > > INSTALL python-scripts > > INSTALL dlfilters > > INSTALL perf_completion-script > > INSTALL perf-tip > > make: Leaving directory '/home/acme/git/perf-tools-next/tools/perf' > > 18: 'import perf' in python : = Ok > > =E2=AC=A2 [acme@toolbx perf-tools-next]$ > > > > root@number:~# perf top > > perf: Segmentation fault > > -------- backtrace -------- > > Segmentation fault (core dumped) > > root@number:~# > > > > Tried also with this, but probably something else is at play: > > > > root@number:~# perf probe -x ~/bin/perf dump_stack > > Added new event: > > probe_perf:dump_stack (on dump_stack in /home/acme/bin/perf) > > > > You can now use it in all perf tools, such as: > > > > perf record -e probe_perf:dump_stack -aR sleep 1 > > > > root@number:~# > > root@number:~# perf trace -e probe_perf:dump_stack/max-stack=3D16/ perf= top > > perf: Segmentation fault > > -------- backtrace -------- > > root@number:~# > > > > Running perf trace on a separate terminal it also doesn't catch > > dump_stack being called (that probe point). > > > > root@number:~# perf top --stdio > > PerfTop: 0 irqs/sec kernel: 0.0% exact: 0.0% lost: 0/0 drop= : 0/0 [4000Hz cycles:P], (all, 32 CPUs) > > -----------------------------------------------------------------------= ---------------------------------------------------------------------------= ---------------------- > > > > perf: Segmentation fault > > Segmentation fault (core dumped) > > root@number:~# > > > > root@number:~# nm ~/bin/perf | grep dump_stack > > 0000000000637eaa T __dump_stack > > 00000000006380fa T dump_stack > > 000000000063816b T sighandler_dump_stack > > root@number:~# > > > > =E2=AC=A2 [acme@toolbx perf-tools-next]$ rpm -q glibc > > glibc-2.41-5.fc42.x86_64 > > root@number:~# uname -a > > Linux number 6.14.8-300.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Thu May 22 1= 9:26:02 UTC 2025 x86_64 GNU/Linux > > root@number:~# > > > > What am I missing? > > For perf top I can do: > ``` > $ sudo /tmp/perf/perf top > ``` > in a different terminal: > ``` > $ sudo killall -11 perf > ``` > then back in the first terminal: > ``` > perf: Segmentation fault > -------- backtrace -------- > #0 0x55ee68647918 in ui__signal_backtrace setup.c:110 > #1 0x7fe2d3849df0 in __restore_rt libc_sigaction.c:0 > #2 0x7fe2d38a49ee in __syscall_cancel_arch syscall_cancel.S:56 > #3 0x7fe2d3899668 in __internal_syscall_cancel cancellation.c:54 > #4 0x7fe2d38996ad in __syscall_cancel cancellation.c:79 > #5 0x7fe2d390d9c6 in __poll poll.c:43 > #6 0x55ee6855dfcb in fdarray__poll array.c:139 > #7 0x55ee68565a05 in perf_evlist__poll evlist.c:391 > #8 0x55ee68673b5a in evlist__poll evlist.c:594 > #9 0x55ee684e7a61 in __cmd_top builtin-top.c:1369 > #10 0x55ee684e9a6c in cmd_top builtin-top.c:1856 > #11 0x55ee6855d1f0 in run_builtin perf.c:351 > #12 0x55ee6855d497 in handle_internal_command perf.c:404 > #13 0x55ee6855d5f0 in run_argv perf.c:451 > #14 0x55ee6855d939 in main perf.c:558 > #15 0x7fe2d3833ca8 in __libc_start_call_main libc_start_call_main.h:74 > #16 0x7fe2d3833d65 in __libc_start_main@@GLIBC_2.34 libc-start.c:128 > #17 0x55ee684b0a91 in _start perf[4ca91] > ``` > As the same symbol code is used for the backtrace then adding the segv > there is likely causing a segv in the signal handler in __dump_stack. Just to note, it would be nice for this to land as I need to rebase: https://lore.kernel.org/lkml/20250529044000.759937-19-irogers@google.com/ due to the machine changes. I believe the patches are WAI as shown in the output. Thanks, Ian > Thanks, > Ian > > > - Arnaldo > > > > > ____ unexpected signal (2) ____ > > > #0 0x5590fb6209b6 in child_test_sig_handler builtin-test.c:243 > > > #1 0x7f4a91e49e20 in __restore_rt libc_sigaction.c:0 > > > #2 0x7f4a91ee4f33 in clock_nanosleep@GLIBC_2.2.5 clock_nanosleep.= c:71 > > > #3 0x7f4a91ef0333 in __nanosleep nanosleep.c:26 > > > #4 0x7f4a91f01f68 in __sleep sleep.c:55 > > > #5 0x5590fb638c63 in test__PERF_RECORD perf-record.c:295 > > > #6 0x5590fb620b43 in run_test_child builtin-test.c:269 > > > #7 0x5590fb5b83ab in start_command run-command.c:127 > > > #8 0x5590fb621572 in start_test builtin-test.c:467 > > > #9 0x5590fb621a47 in __cmd_test builtin-test.c:573 > > > #10 0x5590fb6225ea in cmd_test builtin-test.c:775 > > > #11 0x5590fb5a9099 in run_builtin perf.c:351 > > > #12 0x5590fb5a9340 in handle_internal_command perf.c:404 > > > #13 0x5590fb5a9499 in run_argv perf.c:451 > > > #14 0x5590fb5a97e2 in main perf.c:558 > > > #15 0x7f4a91e33d68 in __libc_start_call_main libc_start_call_main= .h:74 > > > #16 0x7f4a91e33e25 in __libc_start_main@@GLIBC_2.34 libc-start.c:= 128 > > > #17 0x5590fb4fd6d1 in _start perf[436d1] > > > ``` > > > > > > Signed-off-by: Ian Rogers > > > --- > > > v2: Fix NO_BACKTRACE=3D1 build (Arnaldo) > > > --- > > > tools/perf/tests/builtin-test.c | 15 +++++++- > > > tools/perf/ui/tui/setup.c | 2 +- > > > tools/perf/util/debug.c | 68 +++++++++++++++++++++++++++----= -- > > > tools/perf/util/debug.h | 1 + > > > 4 files changed, 73 insertions(+), 13 deletions(-) > > > > > > diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/built= in-test.c > > > index 45d3d8b3317a..80375ca39a37 100644 > > > --- a/tools/perf/tests/builtin-test.c > > > +++ b/tools/perf/tests/builtin-test.c > > > @@ -6,6 +6,9 @@ > > > */ > > > #include > > > #include > > > +#ifdef HAVE_BACKTRACE_SUPPORT > > > +#include > > > +#endif > > > #include > > > #include > > > #include > > > @@ -231,6 +234,16 @@ static jmp_buf run_test_jmp_buf; > > > > > > static void child_test_sig_handler(int sig) > > > { > > > +#ifdef HAVE_BACKTRACE_SUPPORT > > > + void *stackdump[32]; > > > + size_t stackdump_size; > > > +#endif > > > + > > > + fprintf(stderr, "\n---- unexpected signal (%d) ----\n", sig); > > > +#ifdef HAVE_BACKTRACE_SUPPORT > > > + stackdump_size =3D backtrace(stackdump, ARRAY_SIZE(stackdump)); > > > + __dump_stack(stderr, stackdump, stackdump_size); > > > +#endif > > > siglongjmp(run_test_jmp_buf, sig); > > > } > > > > > > @@ -244,7 +257,7 @@ static int run_test_child(struct child_process *p= rocess) > > > > > > err =3D sigsetjmp(run_test_jmp_buf, 1); > > > if (err) { > > > - fprintf(stderr, "\n---- unexpected signal (%d) ----\n",= err); > > > + /* Received signal. */ > > > err =3D err > 0 ? -err : -1; > > > goto err_out; > > > } > > > diff --git a/tools/perf/ui/tui/setup.c b/tools/perf/ui/tui/setup.c > > > index 16c6eff4d241..022534eed68c 100644 > > > --- a/tools/perf/ui/tui/setup.c > > > +++ b/tools/perf/ui/tui/setup.c > > > @@ -108,7 +108,7 @@ static void ui__signal_backtrace(int sig) > > > > > > printf("-------- backtrace --------\n"); > > > size =3D backtrace(stackdump, ARRAY_SIZE(stackdump)); > > > - backtrace_symbols_fd(stackdump, size, STDOUT_FILENO); > > > + __dump_stack(stdout, stackdump, size); > > > > > > exit(0); > > > } > > > diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c > > > index f9ef7d045c92..0c7c6a9e158b 100644 > > > --- a/tools/perf/util/debug.c > > > +++ b/tools/perf/util/debug.c > > > @@ -14,11 +14,18 @@ > > > #ifdef HAVE_BACKTRACE_SUPPORT > > > #include > > > #endif > > > +#include "addr_location.h" > > > #include "color.h" > > > -#include "event.h" > > > #include "debug.h" > > > +#include "event.h" > > > +#include "machine.h" > > > +#include "map.h" > > > #include "print_binary.h" > > > +#include "srcline.h" > > > +#include "symbol.h" > > > +#include "synthetic-events.h" > > > #include "target.h" > > > +#include "thread.h" > > > #include "trace-event.h" > > > #include "ui/helpline.h" > > > #include "ui/ui.h" > > > @@ -298,21 +305,60 @@ void perf_debug_setup(void) > > > libapi_set_print(pr_warning_wrapper, pr_warning_wrapper, pr_deb= ug_wrapper); > > > } > > > > > > +void __dump_stack(FILE *file, void **stackdump, size_t stackdump_siz= e) > > > +{ > > > + /* TODO: async safety. printf, malloc, etc. aren't safe inside = a signal handler. */ > > > + pid_t pid =3D getpid(); > > > + struct machine *machine =3D machine__new_live(/*kernel_maps=3D*= /false, pid); > > > + struct thread *thread =3D NULL; > > > + > > > + if (machine) > > > + thread =3D machine__find_thread(machine, pid, pid); > > > + > > > +#ifdef HAVE_BACKTRACE_SUPPORT > > > + if (!machine || !thread) { > > > + /* > > > + * Backtrace functions are async signal safe. Fall back= on them > > > + * if machine/thread creation fails. > > > + */ > > > + backtrace_symbols_fd(stackdump, stackdump_size, fileno(= file)); > > > + machine__delete(machine); > > > + return; > > > + } > > > +#endif > > > + > > > + for (size_t i =3D 0; i < stackdump_size; i++) { > > > + struct addr_location al; > > > + u64 addr =3D (u64)stackdump[i]; > > > + bool printed =3D false; > > > + > > > + addr_location__init(&al); > > > + if (thread && thread__find_map(thread, PERF_RECORD_MISC= _USER, addr, &al)) { > > > + al.sym =3D map__find_symbol(al.map, al.addr); > > > + if (al.sym) { > > > + fprintf(file, " #%zd %p in %s ", i, = stackdump[i], al.sym->name); > > > + printed =3D true; > > > + } > > > + } > > > + if (!printed) > > > + fprintf(file, " #%zd %p ", i, stackdump[i]); > > > + > > > + map__fprintf_srcline(al.map, al.addr, "", file); > > > + fprintf(file, "\n"); > > > + addr_location__exit(&al); > > > + } > > > + thread__put(thread); > > > + machine__delete(machine); > > > +} > > > + > > > /* Obtain a backtrace and print it to stdout. */ > > > #ifdef HAVE_BACKTRACE_SUPPORT > > > void dump_stack(void) > > > { > > > - void *array[16]; > > > - size_t size =3D backtrace(array, ARRAY_SIZE(array)); > > > - char **strings =3D backtrace_symbols(array, size); > > > - size_t i; > > > - > > > - printf("Obtained %zd stack frames.\n", size); > > > - > > > - for (i =3D 0; i < size; i++) > > > - printf("%s\n", strings[i]); > > > + void *stackdump[32]; > > > + size_t size =3D backtrace(stackdump, ARRAY_SIZE(stackdump)); > > > > > > - free(strings); > > > + __dump_stack(stdout, stackdump, size); > > > } > > > #else > > > void dump_stack(void) {} > > > diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h > > > index a4026d1fd6a3..6b737e195ce1 100644 > > > --- a/tools/perf/util/debug.h > > > +++ b/tools/perf/util/debug.h > > > @@ -85,6 +85,7 @@ void debug_set_display_time(bool set); > > > void perf_debug_setup(void); > > > int perf_quiet_option(void); > > > > > > +void __dump_stack(FILE *file, void **stackdump, size_t stackdump_siz= e); > > > void dump_stack(void); > > > void sighandler_dump_stack(int sig); > > > > > > -- > > > 2.49.0.1204.g71687c7c1d-goog > > >