Re: [PATCH 3/3] kernel/hung_task convert hung_task_panic boot parameter to sysctl

On 3/30/20 10:43 AM, Kees Cook wrote:
...

quoted

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" },

Hi Vlastimil,

Maybe best to delete the above line? Because:

     a) it was added as an example, and now that you have a real use case in this patch,
        the example is no longer required, and

     b) numa_zonelist_order is deprecated, as a boot param. Adding support to it in this
        brand-new mechanism seems to be going a bit in the opposite direction of deprecation.

And, I don't think you really want all the sysctls to be enabled as boot params, right? Your
comment right above sysctl_aliases[] (shown in patch 2) sort of indicates that only some items
are meant to be both sysctl's and boot params. And that makes sense.

In fact, the sysctl_aliases[] is (or could be) effectively the whitelist that Luis Chamberlain
was requesting in another thread. A whitelist makes good sense, for the reasons Luis listed.
As such, keeping it limited to items that we want, seems like the way to go, IMHO.


thanks,
-- 
John Hubbard
NVIDIA

quoted

+	{"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