linux-kernel - [PATCHv2 0/4] perf tools: Fix top crashes

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Date:   Thu, 19 Jul 2018 16:33:41 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Kan Liang <kan.liang@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Lukasz Odzioba <lukasz.odzioba@...el.com>,
        Wang Nan <wangnan0@...wei.com>
Subject: [PATCHv2 0/4] perf tools: Fix top crashes

hi,
perf top is occasionaly crashes on hitting assert, because of
the synthesize function that runs on multiple threads now.

I found some issues with list/tree accessing and this patchset
is trying to fix them.

I was runing 'perf top' in a loop with attached change below
and haven't hit any other new crash. We're either clear now
or it's really hard to hit the rest ;-)

v2 changes:
  - remove the 'struct comm_str' only in the comm_str__put
    when the refcnt drops to 0 (Namhyung)

thanks,
jirka

---
Jiri Olsa (4):
      perf tools: Add threads__get_last_match function
      perf tools: Add threads__set_last_match function
      perf tools: Use last_match threads cache only in single thread mode
      perf tools: Fix struct comm_str removal crash

 tools/perf/util/comm.c    | 15 +++++++++------
 tools/perf/util/machine.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------
 2 files changed, 63 insertions(+), 22 deletions(-)
---
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index ffdc2769ff9f..1b57a66ef779 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1102,6 +1102,8 @@ static int __cmd_top(struct perf_top *top)
 	if (top->nr_threads_synthesize > 1)
 		perf_set_singlethreaded();
 
+	return 0;
+
 	if (perf_hpp_list.socket) {
 		ret = perf_env__read_cpu_topology_map(&perf_env);
 		if (ret < 0)