linux-kernel - [PATCH 3/3] kernel/hung_task convert hung_task

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Date:   Mon, 30 Mar 2020 13:55:35 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Ivan Teterevkov <ivan.teterevkov@...anix.com>,
        Michal Hocko <mhocko@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Guilherme G . Piccoli" <gpiccoli@...onical.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 3/3] kernel/hung_task convert hung_task_panic boot parameter to sysctl

We can now handle sysctl parameters on kernel command line and have
infrastructure to convert legacy command line options that duplicate sysctl
to become a sysctl alias.

This patch converts the hung_task_panic parameter. Note that the sysctl handler
is more strict and allows only 0 and 1, while the legacy parameter allowed
any non-zero value. But there is little reason anyone would not be using 1.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 +-
 fs/proc/proc_sysctl.c                           |  1 +
 kernel/hung_task.c                              | 10 ----------
 3 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 81ff626fc700..e0b8840404a1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1457,7 +1457,7 @@
 			[KNL] Should the hung task detector generate panics.
 			Format: <integer>
 
-			A nonzero value instructs the kernel to panic when a
+			A value of 1 instructs the kernel to panic when a
 			hung task is detected. The default value is controlled
 			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
 			option. The value selected by this boot parameter can
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 97eb0b552bf8..77b1b844b02b 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1743,6 +1743,7 @@ struct sysctl_alias {
  */
 static const struct sysctl_alias sysctl_aliases[] = {
 	{"numa_zonelist_order",		"vm.numa_zonelist_order" },
+	{"hung_task_panic",		"kernel.hung_task_panic" },
 	{ }
 };
 
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 14a625c16cb3..b22b5eeab3cb 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -63,16 +63,6 @@ static struct task_struct *watchdog_task;
 unsigned int __read_mostly sysctl_hung_task_panic =
 				CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
 
-static int __init hung_task_panic_setup(char *str)
-{
-	int rc = kstrtouint(str, 0, &sysctl_hung_task_panic);
-
-	if (rc)
-		return rc;
-	return 1;
-}
-__setup("hung_task_panic=", hung_task_panic_setup);
-
 static int
 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
 {
-- 
2.25.1