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Date: Fri, 20 Nov 2015 09:05:23 +0000
From: 平松雅巳 / HIRAMATU，MASAMI
<masami.hiramatsu.pt@...achi.com>
To: "'Namhyung Kim'" <namhyung@...nel.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>
CC: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Jiri Olsa <jolsa@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
"David Ahern" <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>
Subject: RE: [RFC/PATCH] perf tools: Introduce perf_thread for backtrace
>From: Namhyung Kim [mailto:namhyung@...nel.org]
>
>Backtrace is a crucial info for debugging. And upcoming refcnt
>tracking facility also wants to use it.
>
>So instead of relying on glibc's backtrace_symbols[_fd] which misses
>some (static) functions , use our own symbol searching mechanism. To
>do that, add perf_thread global variable to keep its maps and symbols.
Hmm, I doubt that this can work for debugging situation, because
sometimes backtrace facilities has to debug itself by itself.
For the some (static) functions, I'd rather like to use glibc's
backtrace_symbols and addr2line or even with raw address for
reliability...
Thank you,
>
>The backtrace output from TUI is changed like below. (I made a key
>action to generate a segfault for testing):
>
>Before:
> perf: Segmentation fault
> -------- backtrace --------
> perf[0x544a8b]
> /usr/lib/libc.so.6(+0x33680)[0x7fc46420b680]
> perf[0x54041b]
> perf(perf_evlist__tui_browse_hists+0x91)[0x5432e1]
> perf(cmd_report+0x1d20)[0x43cb10]
> perf[0x487073]
> perf(main+0x62f)[0x42cb1f]
> /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7fc4641f8610]
> perf(_start+0x29)[0x42cc39]
> [0x0]
>
>After:
> perf: Segmentation fault
> -------- backtrace --------
> perf_evsel__hists_browse(+0x43b) in perf [0x54066b]
> perf_evlist__tui_browse_hists(+0x91) in perf [0x543531]
> cmd_report(+0x1d20) in perf [0x43cb50]
> run_builtin(+0x53) in perf [0x4870b3]
> main(+0x634) in perf [0x42cb54]
> __libc_start_main(+0xf0) in libc-2.22.so [0x7fea3577c610]
> _start(+0x29) in perf [0x42cc79]
> [0x0]
>
>Cc: Frederic Weisbecker <fweisbec@...il.com>
>Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>---
> tools/perf/perf.c | 7 +++++-
> tools/perf/ui/tui/setup.c | 21 ++++++++++++++--
> tools/perf/util/util.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/util.h | 5 ++++
> 4 files changed, 92 insertions(+), 3 deletions(-)
>
>diff --git a/tools/perf/perf.c b/tools/perf/perf.c
>index 4bee53c3f796..f77eb440b05c 100644
>--- a/tools/perf/perf.c
>+++ b/tools/perf/perf.c
>@@ -604,6 +604,8 @@ int main(int argc, const char **argv)
> */
> pthread__block_sigwinch();
>
>+ create_perf_thread();
>+
> while (1) {
> static int done_help;
> int was_alias = run_argv(&argc, &argv);
>@@ -615,7 +617,7 @@ int main(int argc, const char **argv)
> fprintf(stderr, "Expansion of alias '%s' failed; "
> "'%s' is not a perf-command\n",
> cmd, argv[0]);
>- goto out;
>+ goto out_destroy;
> }
> if (!done_help) {
> cmd = argv[0] = help_unknown_cmd(cmd);
>@@ -626,6 +628,9 @@ int main(int argc, const char **argv)
>
> fprintf(stderr, "Failed to run command '%s': %s\n",
> cmd, strerror_r(errno, sbuf, sizeof(sbuf)));
>+
>+out_destroy:
>+ destroy_perf_thread();
> out:
> return 1;
> }
>diff --git a/tools/perf/ui/tui/setup.c b/tools/perf/ui/tui/setup.c
>index 7dfeba0a91f3..bc2da884e65a 100644
>--- a/tools/perf/ui/tui/setup.c
>+++ b/tools/perf/ui/tui/setup.c
>@@ -13,6 +13,8 @@
> #include "../libslang.h"
> #include "../keysyms.h"
> #include "tui.h"
>+#include "../../util/symbol.h"
>+#include "../../util/thread.h"
>
> static volatile int ui__need_resize;
>
>@@ -96,14 +98,29 @@ int ui__getch(int delay_secs)
> static void ui__signal_backtrace(int sig)
> {
> void *stackdump[32];
>- size_t size;
>+ size_t size, i;
>
> ui__exit(false);
> psignal(sig, "perf");
>
> printf("-------- backtrace --------\n");
> size = backtrace(stackdump, ARRAY_SIZE(stackdump));
>- backtrace_symbols_fd(stackdump, size, STDOUT_FILENO);
>+ /* skip first two stack frame (for this function and signal stack) */
>+ for (i = 2; i < size; i++) {
>+ struct addr_location al = {
>+ .sym = NULL,
>+ };
>+
>+ thread__find_addr_location(perf_thread, PERF_RECORD_MISC_USER,
>+ MAP__FUNCTION, (long)stackdump[i], &al);
>+
>+ if (al.sym)
>+ printf("%s(+0x%"PRIx64") in ", al.sym->name,
>+ map__map_ip(al.map, (u64)stackdump[i]) - al.sym->start);
>+ if (al.map)
>+ printf("%s ", al.map->dso->short_name);
>+ printf("[0x%lx]\n", (unsigned long)stackdump[i]);
>+ }
>
> exit(0);
> }
>diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
>index 75759aebc7b8..f1a26ea14053 100644
>--- a/tools/perf/util/util.c
>+++ b/tools/perf/util/util.c
>@@ -16,6 +16,9 @@
> #include <linux/kernel.h>
> #include <unistd.h>
> #include "callchain.h"
>+#include "machine.h"
>+#include "thread.h"
>+#include "thread_map.h"
>
> struct callchain_param callchain_param = {
> .mode = CHAIN_GRAPH_ABS,
>@@ -696,3 +699,62 @@ fetch_kernel_version(unsigned int *puint, char *str,
> *puint = (version << 16) + (patchlevel << 8) + sublevel;
> return 0;
> }
>+
>+
>+static int process_event(struct perf_tool *tool, union perf_event *event,
>+ struct perf_sample *sample, struct machine *machine)
>+{
>+ switch (event->header.type) {
>+ case PERF_RECORD_COMM:
>+ return tool->comm(tool, event, sample, machine);
>+ case PERF_RECORD_MMAP:
>+ return tool->mmap(tool, event, sample, machine);
>+ case PERF_RECORD_MMAP2:
>+ return tool->mmap2(tool, event, sample, machine);
>+ default:
>+ break;
>+ }
>+ return 0;
>+}
>+
>+struct thread *perf_thread;
>+
>+void create_perf_thread(void)
>+{
>+ struct perf_tool tool = {
>+ .comm = perf_event__process_comm,
>+ .mmap = perf_event__process_mmap,
>+ .mmap2 = perf_event__process_mmap2,
>+ };
>+ struct thread_map *tm;
>+ struct machine *machine;
>+ int pid = getpid();
>+
>+ machine = machine__new_host();
>+ if (machine == NULL)
>+ return;
>+
>+ tm = thread_map__new_dummy();
>+ if (tm == NULL) {
>+ machine__delete(machine);
>+ return;
>+ }
>+
>+ thread_map__set_pid(tm, 0, pid);
>+
>+ perf_event__synthesize_thread_map(&tool, tm, process_event, machine,
>+ false, 500);
>+
>+ perf_thread = machine__find_thread(machine, pid, pid);
>+ BUG_ON(perf_thread == NULL);
>+
>+ thread_map__put(tm);
>+}
>+
>+void destroy_perf_thread(void)
>+{
>+ struct machine *machine = perf_thread->mg->machine;
>+
>+ machine__delete_threads(machine);
>+ machine__delete(machine);
>+}
>diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
>index dcc659017976..630e145049aa 100644
>--- a/tools/perf/util/util.h
>+++ b/tools/perf/util/util.h
>@@ -358,4 +358,9 @@ int fetch_kernel_version(unsigned int *puint,
> #define KVER_FMT "%d.%d.%d"
> #define KVER_PARAM(x) KVER_VERSION(x), KVER_PATCHLEVEL(x), KVER_SUBLEVEL(x)
>
>+extern struct thread *perf_thread;
>+
>+void create_perf_thread(void);
>+void destroy_perf_thread(void);
>+
> #endif /* GIT_COMPAT_UTIL_H */
>--
>2.6.2
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