linux-kernel - [PATCH] sched/debug: print column titles of show_state

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Message-ID: <20210812140934.87476-1-shirish.s@amd.com>
Date:   Thu, 12 Aug 2021 19:39:34 +0530
From:   Shirish S <shirish.s@....com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        "Mel Gorman" <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, Shirish S <shirish.s@....com>
Subject: [PATCH] sched/debug: print column titles of show_state_filter()

This addition in the debug output shall improve readablitly..
Its not intuitive for users that the pid printed in last column
is of parent process.

Without this patch:
	localhost ~ # dmesg -w &
	localhost ~ # echo w > /proc/sysrq-trigger
	[22148.730225] sysrq: Show Blocked State
	localhost ~ #

With this patch:
	localhost ~ # dmesg -w &
	localhost ~ # echo w > /proc/sysrq-trigger
	[   99.979365] sysrq: Show Blocked State
-->	[   99.983471]   task                        PC stack   pid father
	localhost ~ #

v2: Dropped #ifdef logic
v3: Sample output in commit message

Signed-off-by: Shirish S <shirish.s@....com>
Suggested-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/sched/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 20ffcc044134..d9c7014870d5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8174,6 +8174,9 @@ void show_state_filter(unsigned int state_filter)
 {
 	struct task_struct *g, *p;
 
+	pr_info("  task%*s", BITS_PER_LONG == 32 ? 38 : 46,
+		"PC stack   ppid\n");
+
 	rcu_read_lock();
 	for_each_process_thread(g, p) {
 		/*
-- 
2.17.1