perf script: Fix crash when processing recorded stat data

tonyj-suse · acmel · commit 8bf8c6da53c2 · 2019-01-21T11:29:07.000-03:00
While updating perf to work with Python3 and Python2 I noticed that the stat-cpi script was dumping core. $ perf stat -e cycles,instructions record -o /tmp/perf.data /bin/false Performance counter stats for '/bin/false': 802,148 cycles 604,622 instructions 802,148 cycles 604,622 instructions 0.001445842 seconds time elapsed $ perf script -i /tmp/perf.data -s scripts/python/stat-cpi.py Segmentation fault (core dumped) ... ... rblist=rblist@entry=0xb2a200 <rt_stat>, new_entry=new_entry@entry=0x7ffcb755c310) at util/rblist.c:33 ctx=<optimized out>, type=<optimized out>, create=<optimized out>, cpu=<optimized out>, evsel=<optimized out>) at util/stat-shadow.c:118 ctx=<optimized out>, type=<optimized out>, st=<optimized out>) at util/stat-shadow.c:196 count=count@entry=727442, cpu=cpu@entry=0, st=0xb2a200 <rt_stat>) at util/stat-shadow.c:239 config=config@entry=0xafeb40 <stat_config>, counter=counter@entry=0x133c6e0) at util/stat.c:372 ... ... The issue is that since 1fcd039 perf_stat__update_shadow_stats now calls update_runtime_stat passing rt_stat rather than calling update_stats but perf_stat__init_shadow_stats has never been called to initialize rt_stat in the script path processing recorded stat data. Since I can't see any reason why perf_stat__init_shadow_stats() is presently initialized like it is in builtin-script.c::perf_sample__fprint_metric() [4bd1bef] I'm proposing it instead be initialized once in __cmd_script Committer testing: After applying the patch: # perf script -i /tmp/perf.data -s tools/perf/scripts/python/stat-cpi.py 0.001970: cpu -1, thread -1 -> cpi 1.709079 (1075684/629394) # No segfault. Signed-off-by: Tony Jones <tonyj@suse.de> Reviewed-by: Jiri Olsa <jolsa@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Jin Yao <yao.jin@linux.intel.com> Fixes: 1fcd039 ("perf stat: Update per-thread shadow stats") Link: http://lkml.kernel.org/r/20190120191414.12925-1-tonyj@suse.de Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
@@ -1681,13 +1681,8 @@ static void perf_sample__fprint_metric(struct perf_script *script,
 		.force_header = false,
 	};
 	struct perf_evsel *ev2;
-	static bool init;
 	u64 val;
 
-	if (!init) {
-		perf_stat__init_shadow_stats();
-		init = true;
-	}
 	if (!evsel->stats)
 		perf_evlist__alloc_stats(script->session->evlist, false);
 	if (evsel_script(evsel->leader)->gnum++ == 0)
@@ -2359,6 +2354,8 @@ static int __cmd_script(struct perf_script *script)
 
 	signal(SIGINT, sig_handler);
 
+	perf_stat__init_shadow_stats();
+
 	/* override event processing functions */
 	if (script->show_task_events) {
 		script->tool.comm = process_comm_event;
