linux-kernel - [PATCH 2/2] perf trace: Fix call-graph output

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Date:   Tue, 30 Jan 2018 11:00:53 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     acme@...nel.org
Cc:     alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [PATCH 2/2] perf trace: Fix call-graph output

Recently, Arnaldo fixed global vs event specific --max-stack usage
with commit bd3dda9ab0fb ("perf trace: Allow overriding global
--max-stack per event"). This commit is having a regression when
we don't use --max-stack at all with perf trace. Ex,

  $ ./perf trace record -g ls
  $ ./perf trace -i perf.data
     0.076 ( 0.002 ms): ls/9109 brk(
     0.196 ( 0.008 ms): ls/9109 access(filename: 0x9f998b70, mode: R
     0.209 ( 0.031 ms): ls/9109 open(filename: 0x9f998978, flags: CLOEXEC

This is missing call-traces.
After patch:

  $ ./perf trace -i perf.data
     0.076 ( 0.002 ms): ls/9109 brk(
                                do_syscall_trace_leave ([kernel.kallsyms])
                                [0] ([unknown])
                                syscall_exit_work ([kernel.kallsyms])
                                brk (/usr/lib64/ld-2.17.so)
                                _dl_sysdep_start (/usr/lib64/ld-2.17.so)
                                _dl_start_final (/usr/lib64/ld-2.17.so)
                                _dl_start (/usr/lib64/ld-2.17.so)
                                _start (/usr/lib64/ld-2.17.so)
     0.196 ( 0.008 ms): ls/9109 access(filename: 0x9f998b70, mode: R
                                do_syscall_trace_leave ([kernel.kallsyms])
                                [0] ([unknown])

Fixes: bd3dda9ab0fb ("perf trace: Allow overriding global --max-stack per event")
Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
---
 tools/perf/builtin-trace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 17d11de..e90f5c3 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1661,9 +1661,12 @@ static int trace__resolve_callchain(struct trace *trace, struct perf_evsel *evse
 				    struct callchain_cursor *cursor)
 {
 	struct addr_location al;
+	int max_stack = evsel->attr.sample_max_stack ?
+			evsel->attr.sample_max_stack :
+			trace->max_stack;
 
 	if (machine__resolve(trace->host, &al, sample) < 0 ||
-	    thread__resolve_callchain(al.thread, cursor, evsel, sample, NULL, NULL, evsel->attr.sample_max_stack))
+	    thread__resolve_callchain(al.thread, cursor, evsel, sample, NULL, NULL, max_stack))
 		return -1;
 
 	return 0;
-- 
1.8.3.1