perf tools: Fix synthesizing tracepoint names from the perf.data headers

We need to use the per event info snapshoted at record time to
synthesize the events name, so do it just after reading the perf.data
headers, when we already processed the /sys events data, otherwise we'll
end up using the local /sys that only by sheer luck will have the same
tracepoint ID -> real event association.

Example:

  # uname -a
  Linux felicio.ghostprotocols.net 3.4.0-rc5+ svenkatr#1 SMP Sat May 19 15:27:11 BRT 2012 x86_64 x86_64 x86_64 GNU/Linux
  # perf record -e sched:sched_switch usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.015 MB perf.data (~648 samples) ]
  # cat /t/events/sched/sched_switch/id
  279
  # perf evlist -v
  sched:sched_switch: sample_freq=1, type: 2, config: 279, size: 80, sample_type: 1159, read_format: 7, disabled: 1, inherit: 1, mmap: 1, comm: 1, enable_on_exec: 1, sample_id_all: 1, exclude_guest: 1
  #

So on the above machine the sched:sched_switch has tracepoint id 279, but on
the machine were we'll analyse it it has a different id:

  $ cat /t/events/sched/sched_switch/id
  56
  $ perf evlist -i /tmp/perf.data
  kmem:mm_balancedirty_writeout
  $ cat /t/events/kmem/mm_balancedirty_writeout/id
  279

With this fix:

  $ perf evlist -i /tmp/perf.data
  sched:sched_switch

Reported-by: Dmitry Antipov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: acmel

tools/perf/util/header.c

@@ -2093,6 +2093,35 @@ static int read_attr(int fd, struct perf_header *ph,
 	return ret <= 0 ? -1 : 0;
 }
 
+static int perf_evsel__set_tracepoint_name(struct perf_evsel *evsel)
+{
+	struct event_format *event = trace_find_event(evsel->attr.config);
+	char bf[128];
+
+	if (event == NULL)
+		return -1;
+
+	snprintf(bf, sizeof(bf), "%s:%s", event->system, event->name);
+	evsel->name = strdup(bf);
+	if (event->name == NULL)
+		return -1;
+
+	return 0;
+}
+
+static int perf_evlist__set_tracepoint_names(struct perf_evlist *evlist)
+{
+	struct perf_evsel *pos;
+
+	list_for_each_entry(pos, &evlist->entries, node) {
+		if (pos->attr.type == PERF_TYPE_TRACEPOINT &&
+		    perf_evsel__set_tracepoint_name(pos))
+			return -1;
+	}
+
+	return 0;
+}
+
 int perf_session__read_header(struct perf_session *session, int fd)
 {
 	struct perf_header *header = &session->header;
@@ -2174,6 +2203,9 @@ int perf_session__read_header(struct perf_session *session, int fd)
 
 	lseek(fd, header->data_offset, SEEK_SET);
 
+	if (perf_evlist__set_tracepoint_names(session->evlist))
+		goto out_delete_evlist;
+
 	header->frozen = 1;
 	return 0;
 out_errno: