perf trace: Handle multiple threads better wrt syscalls being intermixed

 $ trace time taskset -c 0 usleep 1
   0.845 ( 0.021 ms): time/16722 wait4(upid: 4294967295, stat_addr: 0x7fff17f443d4, ru: 0x7fff17f44438 ) ...
   0.865 ( 0.008 ms): time/16723 execve(arg0: 140733595272004, arg1: 140733595272720, arg2: 140733595272768, arg3: 139755107218496, arg4: 7307199665339051828, arg5: 3) = -2
   2.395 ( 1.523 ms): taskset/16723 execve(arg0: 140733595272013, arg1: 140733595272720, arg2: 140733595272768, arg3: 139755107218496, arg4: 7307199665339051828, arg5: 3) = 0
   2.411 ( 0.002 ms): taskset/16723 brk(                                                                  ) = 0x1915000
   3.300 ( 0.058 ms): usleep/16723 nanosleep(rqtp: 0x7ffff4ada190                                        ) = 0
 <SNIP>
   3.305 ( 0.000 ms): usleep/16723 exit_group(
   3.363 ( 2.539 ms): time/16722  ... [continued]: wait4()) = 16723
   3.366 ( 0.001 ms): time/16722 rt_sigaction(sig: INT, act: 0x7fff17f44160, oact: 0x7fff17f44200, sigsetsize: 8) = 0

We we're not seeing this line:

  0.845 ( 0.021 ms): time/16722 wait4(upid: 4294967295, stat_addr: 0x7fff17f443d4, ru: 0x7fff17f44438 ) ...

just the one when it finishes:

  3.363 ( 2.539 ms): time/16722  ... [continued]: wait4()) = 16723

Still some issues left till we move to ordered_samples when multiple
CPUs/threads are involved...

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-zq9x30a1ky3djqewqn2v3ja3@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -1220,6 +1220,7 @@ struct trace {
 	} syscalls;
 	struct record_opts	opts;
 	struct machine		*host;
+	struct thread		*current;
 	u64			base_time;
 	FILE			*output;
 	unsigned long		nr_events;
@@ -1642,6 +1643,29 @@ static void thread__update_stats(struct thread_trace *ttrace,
 	update_stats(stats, duration);
 }
 
+static int trace__printf_interrupted_entry(struct trace *trace, struct perf_sample *sample)
+{
+	struct thread_trace *ttrace;
+	u64 duration;
+	size_t printed;
+
+	if (trace->current == NULL)
+		return 0;
+
+	ttrace = thread__priv(trace->current);
+
+	if (!ttrace->entry_pending)
+		return 0;
+
+	duration = sample->time - ttrace->entry_time;
+
+	printed  = trace__fprintf_entry_head(trace, trace->current, duration, sample->time, trace->output);
+	printed += fprintf(trace->output, "%-70s) ...\n", ttrace->entry_str);
+	ttrace->entry_pending = false;
+
+	return printed;
+}
+
 static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
 			    union perf_event *event __maybe_unused,
 			    struct perf_sample *sample)
@@ -1673,6 +1697,8 @@ static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
 			return -1;
 	}
 
+	printed += trace__printf_interrupted_entry(trace, sample);
+
 	ttrace->entry_time = sample->time;
 	msg = ttrace->entry_str;
 	printed += scnprintf(msg + printed, 1024 - printed, "%s(", sc->name);
@@ -1688,6 +1714,8 @@ static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
 	} else
 		ttrace->entry_pending = true;
 
+	trace->current = thread;
+
 	return 0;
 }