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Date: Fri, 20 Nov 2015 09:10:44 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: 平松雅巳 / HIRAMATU，MASAMI
<masami.hiramatsu.pt@...achi.com>
Cc: 'Namhyung Kim' <namhyung@...nel.org>,
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
Em Fri, Nov 20, 2015 at 09:05:23AM +0000, 平松雅巳 / HIRAMATU，MASAMI escreveu:
> >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.
That is a valid point, possibly we can have both and when we think that
the code we rely on for resolving symbols has issues, activate the
other, more expensive, binutils/elfutils spawned command line utilities
to do compare the results?
> 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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