perf record: Fix continue profiling after draining the buffer

[ Upstream commit e16c2ce ]

Commit da23133 ("perf record: Use an eventfd to wakeup when
done") uses eventfd() to solve a rare race where the setting and
checking of 'done' which add done_fd to pollfd.  When draining buffer,
revents of done_fd is 0 and evlist__filter_pollfd function returns a
non-zero value.  As a result, perf record does not stop profiling.

The following simple scenarios can trigger this condition:

  # sleep 10 &
  # perf record -p $!

After the sleep process exits, perf record should stop profiling and exit.
However, perf record keeps running.

If pollfd revents contains only POLLERR or POLLHUP, perf record
indicates that buffer is draining and need to stop profiling.  Use
fdarray_flag__nonfilterable() to set done eventfd to nonfilterable
objects, so that evlist__filter_pollfd() does not filter and check done
eventfd.

Fixes: da23133 ("perf record: Use an eventfd to wakeup when done")
Signed-off-by: Yang Jihong <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Tested-by: Jiri Olsa <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alexey Budankov <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

tools/perf/builtin-record.c

@@ -1666,7 +1666,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		status = -1;
 		goto out_delete_session;
 	}
-	err = evlist__add_pollfd(rec->evlist, done_fd);
+	err = evlist__add_wakeup_eventfd(rec->evlist, done_fd);
 	if (err < 0) {
 		pr_err("Failed to add wakeup eventfd to poll list\n");
 		status = err;

tools/perf/util/evlist.c

@@ -508,6 +508,14 @@ int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask)
 	return perf_evlist__filter_pollfd(&evlist->core, revents_and_mask);
 }
 
+#ifdef HAVE_EVENTFD_SUPPORT
+int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd)
+{
+	return perf_evlist__add_pollfd(&evlist->core, fd, NULL, POLLIN,
+				       fdarray_flag__nonfilterable);
+}
+#endif
+
 int evlist__poll(struct evlist *evlist, int timeout)
 {
 	return perf_evlist__poll(&evlist->core, timeout);

tools/perf/util/evlist.h

@@ -160,6 +160,10 @@ perf_evlist__find_tracepoint_by_name(struct evlist *evlist,
 int evlist__add_pollfd(struct evlist *evlist, int fd);
 int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask);
 
+#ifdef HAVE_EVENTFD_SUPPORT
+int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd);
+#endif
+
 int evlist__poll(struct evlist *evlist, int timeout);
 
 struct evsel *perf_evlist__id2evsel(struct evlist *evlist, u64 id);