linux-kernel - [tip: sched/core] sched/debug: Reset watchdog on all CPUs while processing sysrq-t

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Date:   Fri, 17 Jan 2020 10:08:42 -0000
From:   "tip-bot2 for Wei Li" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Wei Li <liwei391@...wei.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] sched/debug: Reset watchdog on all CPUs while
 processing sysrq-t

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     02d4ac5885a18d326b500b94808f0956dcce2832
Gitweb:        https://git.kernel.org/tip/02d4ac5885a18d326b500b94808f0956dcce2832
Author:        Wei Li <liwei391@...wei.com>
AuthorDate:    Thu, 26 Dec 2019 16:52:24 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 17 Jan 2020 10:19:20 +01:00

sched/debug: Reset watchdog on all CPUs while processing sysrq-t

Lengthy output of sysrq-t may take a lot of time on slow serial console
with lots of processes and CPUs.

So we need to reset NMI-watchdog to avoid spurious lockup messages, and
we also reset softlockup watchdogs on all other CPUs since another CPU
might be blocked waiting for us to process an IPI or stop_machine.

Add to sysrq_sched_debug_show() as what we did in show_state_filter().

Signed-off-by: Wei Li <liwei391@...wei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Link: https://lkml.kernel.org/r/20191226085224.48942-1-liwei391@huawei.com
---
 kernel/sched/debug.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index f7e4579..879d3cc 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -751,9 +751,16 @@ void sysrq_sched_debug_show(void)
 	int cpu;
 
 	sched_debug_header(NULL);
-	for_each_online_cpu(cpu)
+	for_each_online_cpu(cpu) {
+		/*
+		 * Need to reset softlockup watchdogs on all CPUs, because
+		 * another CPU might be blocked waiting for us to process
+		 * an IPI or stop_machine.
+		 */
+		touch_nmi_watchdog();
+		touch_all_softlockup_watchdogs();
 		print_cpu(NULL, cpu);
-
+	}
 }
 
 /*