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Date: Mon, 23 Nov 2015 18:39:36 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...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>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [RFC/PATCH] perf tools: Introduce perf_thread for backtrace
Em Fri, Nov 20, 2015 at 03:03:03PM +0900, Namhyung Kim escreveu:
> 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.
>
> The backtrace output from TUI is changed like below. (I made a key
> action to generate a segfault for testing):
This is a really nice use of what we have, I guess we could simplify
things further, not having to create a struct machine, as we have just
one thread, and we're not interested in kernel addresses, so no need for
kmaps, etc.
But as-is it already looks better than what we were using :-)
I'll try testing it further and will probably switch to using it if
nobody voices any problem we haven't realised with such approach.
- Arnaldo
> 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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