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

JIRA: https://issues.redhat.com/browse/RHEL-68347

upstream
========
commit 39f473f
Author: Anubhav Shelat <ashelat@redhat.com>
Date: Wed Jul 16 16:39:15 2025 -0400

description
===========
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 <ashelat@redhat.com>
    Link: https://lore.kernel.org/r/20250716203914.45772-2-ashelat@redhat.com
    Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Signed-off-by: Anubhav Shelat <ashelat@redhat.com>

Author: AnubhavS1

tools/perf/builtin-sched.c

@@ -2174,6 +2174,11 @@ static void timehist_print_sample(struct perf_sched *sched,
 		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)