perf sched timehist: decode process names of processes in zombie state

Previously when running perf trace timehist --state, when recording
processes in the zombie state the process name would not be decoded
properly and appears with just the PID:

1140057.412177 [0006] Mutter Input Th[3139/3104] 0.956 0.019 0.041 S
1140057.412222 [0012] :1248612[1248612] 0.000 0.000 0.332 Z
1140057.412275 [0004] <idle> 0.052 0.052 0.953 I
1140057.412284 [0008] <idle> 0.070 0.070 0.932 I
1140057.412333 [0004] KMS thread[3126/3104] 0.953 0.112 0.058 S

Now some extra processing has been added to decode the process name:

1140057.412177 [0006] Mutter Input Th[3139/3104] 0.956 0.019 0.041 S
1140057.412222 [0012] sleep[1248612] 0.000 0.000 0.332 Z
1140057.412275 [0004] <idle> 0.052 0.052 0.953 I
1140057.412284 [0008] <idle> 0.070 0.070 0.932 I
1140057.412333 [0004] KMS thread[3126/3104] 0.953 0.112 0.058 S

Signed-off-by: Anubhav Shelat <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/builtin-sched.c

···
 		printf(" ");
 	}
 
+	if (!thread__comm_set(thread)) {
+                const char *prev_comm = evsel__strval(evsel, sample, "prev_comm");
+                thread__set_comm(thread, prev_comm, sample->time);
+        }
+
 	printf(" %-*s ", comm_width, timehist_get_commstr(thread));
 
 	if (sched->show_prio)