linux-kernel - [PATCH] Modify the explanation and documentation related to watchdog thread

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Message-Id: <1616554602-1857-1-git-send-email-wangqing@vivo.com>
Date:   Wed, 24 Mar 2021 10:56:39 +0800
From:   Wang Qing <wangqing@...o.com>
To:     Jonathan Corbet <corbet@....net>, Wang Qing <wangqing@...o.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Santosh Sivaraj <santosh@...six.org>,
        Petr Mladek <pmladek@...e.com>, Andrey Ignatov <rdna@...com>,
        "Guilherme G. Piccoli" <gpiccoli@...onical.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Modify the explanation and documentation related to watchdog thread

"watchdog/%u" threads has be replaced by cpu_stop_work, So we need to modify 
the explanation and documentation related to this.

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 .../admin-guide/kernel-per-CPU-kthreads.rst          | 20 --------------------
 kernel/watchdog.c                                    | 12 ++++--------
 2 files changed, 4 insertions(+), 28 deletions(-)

diff --git a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
index 531f689..5e51ee5
--- a/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
+++ b/Documentation/admin-guide/kernel-per-CPU-kthreads.rst
@@ -332,23 +332,3 @@ To reduce its OS jitter, do at least one of the following:
 	kthreads from being created in the first place.  However, please
 	note that this will not eliminate OS jitter, but will instead
 	shift it to RCU_SOFTIRQ.
-
-Name:
-  watchdog/%u
-
-Purpose:
-  Detect software lockups on each CPU.
-
-To reduce its OS jitter, do at least one of the following:
-
-1.	Build with CONFIG_LOCKUP_DETECTOR=n, which will prevent these
-	kthreads from being created in the first place.
-2.	Boot with "nosoftlockup=0", which will also prevent these kthreads
-	from being created.  Other related watchdog and softlockup boot
-	parameters may be found in Documentation/admin-guide/kernel-parameters.rst
-	and Documentation/watchdog/watchdog-parameters.rst.
-3.	Echo a zero to /proc/sys/kernel/watchdog to disable the
-	watchdog timer.
-4.	Echo a large number of /proc/sys/kernel/watchdog_thresh in
-	order to reduce the frequency of OS jitter due to the watchdog
-	timer down to a level that is acceptable for your workload.
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 7110906..d7fb4fb
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -92,7 +92,7 @@ __setup("nmi_watchdog=", hardlockup_panic_setup);
  * own hardlockup detector.
  *
  * watchdog_nmi_enable/disable can be implemented to start and stop when
- * softlockup watchdog threads start and stop. The arch must select the
+ * softlockup watchdog start and stop. The arch must select the
  * SOFTLOCKUP_DETECTOR Kconfig.
  */
 int __weak watchdog_nmi_enable(unsigned int cpu)
@@ -322,7 +322,7 @@ static DEFINE_PER_CPU(struct completion, softlockup_completion);
 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 
 /*
- * The watchdog thread function - touches the timestamp.
+ * The watchdog feed function - touches the timestamp.
  *
  * It only runs once every sample_period seconds (4 seconds by
  * default) to reset the softlockup timestamp. If this gets delayed
@@ -551,11 +551,7 @@ static void lockup_detector_reconfigure(void)
 }
 
 /*
- * Create the watchdog thread infrastructure and configure the detector(s).
- *
- * The threads are not unparked as watchdog_allowed_mask is empty.  When
- * the threads are successfully initialized, take the proper locks and
- * unpark the threads in the watchdog_cpumask if the watchdog is enabled.
+ * Create the watchdog infrastructure and configure the detector(s).
  */
 static __init void lockup_detector_setup(void)
 {
@@ -621,7 +617,7 @@ void lockup_detector_soft_poweroff(void)
 
 #ifdef CONFIG_SYSCTL
 
-/* Propagate any changes to the watchdog threads */
+/* Propagate any changes to the watchdog infrastructure */
 static void proc_watchdog_update(void)
 {
 	/* Remove impossible cpus to keep sysctl output clean. */
-- 
2.7.4