From 1a5620671a1b6fd9cc08761677d050f1702f910c Mon Sep 17 00:00:00 2001
From: Waiman Long <longman@redhat.com>
Date: Thu, 18 Nov 2021 14:14:37 -0500
Subject: [PATCH] clocksource: Reduce the default clocksource_watchdog()
retries to 2
Git-commit: 1a5620671a1b6fd9cc08761677d050f1702f910c
Patch-mainline: v5.16-rc1
References: bsc#1192724
With the previous patch, there is an extra watchdog read in each retry.
Now the total number of clocksource reads is increased to 4 per iteration.
In order to avoid increasing the clock skew check overhead, the default
maximum number of retries is reduced from 3 to 2 to maintain the same 12
clocksource reads in the worst case.
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Jiri Wiesner <jwiesner@suse.de>
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++--
kernel/time/clocksource.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9725c546a0d4..3ea934b034f7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -603,8 +603,8 @@
clocksource.max_cswd_read_retries= [KNL]
Number of clocksource_watchdog() retries due to
external delays before the clock will be marked
- unstable. Defaults to three retries, that is,
- four attempts to read the clock under test.
+ unstable. Defaults to two retries, that is,
+ three attempts to read the clock under test.
clocksource.verify_n_cpus= [KNL]
Limit the number of CPUs checked for clocksources
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index bcad1a1e5dcf..b7e52a642948 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -199,7 +199,7 @@ void clocksource_mark_unstable(struct clocksource *cs)
spin_unlock_irqrestore(&watchdog_lock, flags);
}
-ulong max_cswd_read_retries = 3;
+ulong max_cswd_read_retries = 2;
module_param(max_cswd_read_retries, ulong, 0644);
EXPORT_SYMBOL_GPL(max_cswd_read_retries);
static int verify_n_cpus = 8;
--
2.26.2