[PATCH 1/2] doc: Fixup definition of rcupdate.rcu_task_stall_timeout

[PATCH 1/2] doc: Fixup definition of rcupdate.rcu_task_stall_timeout

[Zhenzhong Duan]

A positive value of rcupdate.rcu_task_stall_timeout is an interval
in seconds rather than jiffies.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
---
 Documentation/RCU/stallwarn.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 1ab70c3..13e88fc 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -153,7 +153,7 @@ rcupdate.rcu_task_stall_timeout
 	This boot/sysfs parameter controls the RCU-tasks stall warning
 	interval.  A value of zero or less suppresses RCU-tasks stall
 	warnings.  A positive value sets the stall-warning interval
-	in jiffies.  An RCU-tasks stall warning starts with the line:
+	in seconds.  An RCU-tasks stall warning starts with the line:
 
 		INFO: rcu_tasks detected stalls on tasks:
 
-- 
1.8.3.1

[PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

[Zhenzhong Duan]

As stated in "Documentation/lockup-watchdogs.txt:line 22", the default
behaivor after 'hardlockup' is to stay locked up rather than panic.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2b8ee90..fcc9579 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2769,7 +2769,7 @@
 			0 - turn hardlockup detector in nmi_watchdog off
 			1 - turn hardlockup detector in nmi_watchdog on
 			When panic is specified, panic when an NMI watchdog
-			timeout occurs (or 'nopanic' to override the opposite
+			timeout occurs (or 'nopanic' which is the opposite
 			default). To disable both hard and soft lockup detectors,
 			please see 'nowatchdog'.
 			This is useful when you use a panic=... timeout and
-- 
1.8.3.1

Re: [PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

[Zhenzhong Duan]

On 2019/4/14 11:11, Zhenzhong Duan wrote:
> As stated in "Documentation/lockup-watchdogs.txt:line 22", the default
> behaivor after 'hardlockup' is to stay locked up rather than panic.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> ---
>   Documentation/admin-guide/kernel-parameters.txt | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 2b8ee90..fcc9579 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2769,7 +2769,7 @@
>   			0 - turn hardlockup detector in nmi_watchdog off
>   			1 - turn hardlockup detector in nmi_watchdog on
>   			When panic is specified, panic when an NMI watchdog
> -			timeout occurs (or 'nopanic' to override the opposite
> +			timeout occurs (or 'nopanic' which is the opposite
>   			default). To disable both hard and soft lockup detectors,
>   			please see 'nowatchdog'.
>   			This is useful when you use a panic=... timeout and

Hi Maintainers,

Any comment?


Thanks

Zhenzhong

Re: [PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

[Steven Rostedt]

As nobody else commented, I will ;)

Hi Zhenzhong!

On Sun, 14 Apr 2019 11:11:04 +0800
Zhenzhong Duan <zhenzhong.duan@oracle.com> wrote:

> As stated in "Documentation/lockup-watchdogs.txt:line 22", the default
> behaivor after 'hardlockup' is to stay locked up rather than panic.

That actually says:

 A 'hardlockup' is defined as a bug that causes the CPU to loop in
 kernel mode for more than 10 seconds (see "Implementation" below for 
 details), without letting other interrupts have a chance to run.
 Similarly to the softlockup case, the current stack trace is displayed
 upon detection and the system will stay locked up unless the default
 behavior is changed, which can be done through a sysctl,
 'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC",
 and a kernel parameter, "nmi_watchdog"

If your config has:

 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y

The kernel will panic on hard lockup by default unless you add nopanic.

If your config has:

 # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set

Then the default will be not to panic unless you add "panic" to the
kernel command line.

> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 2b8ee90..fcc9579 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2769,7 +2769,7 @@
>  			0 - turn hardlockup detector in nmi_watchdog off
>  			1 - turn hardlockup detector in nmi_watchdog on
>  			When panic is specified, panic when an NMI watchdog
> -			timeout occurs (or 'nopanic' to override the opposite
> +			timeout occurs (or 'nopanic' which is the opposite
>  			default). To disable both hard and soft lockup detectors,

Honestly, I think the original text states what it does better than
your update. Because the nopanic is added to override the "opposite
default" which is if the config was set to do so.

That said, this all still can be explained better. What about:

        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
                        Format: [panic,][nopanic,][num]
                        Valid num: 0 or 1
                        0 - turn hardlockup detector in nmi_watchdog off
                        1 - turn hardlockup detector in nmi_watchdog on
                        When panic is specified, panic when an NMI watchdog
                        timeout occurs (or 'nopanic' to not panic on an NMI
			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
                        To disable both hard and soft lockup detectors,
                        please see 'nowatchdog'.
                        This is useful when you use a panic=... timeout and
                        need the box quickly up again.

-- Steve


>  			please see 'nowatchdog'.
>  			This is useful when you use a panic=... timeout and

Re: [PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

[Joel Fernandes]

On Fri, May 10, 2019 at 02:47:49PM -0400, Steven Rostedt wrote:
> 
> As nobody else commented, I will ;)
> 
> Hi Zhenzhong!
> 
> On Sun, 14 Apr 2019 11:11:04 +0800
> Zhenzhong Duan <zhenzhong.duan@oracle.com> wrote:
> 
> > As stated in "Documentation/lockup-watchdogs.txt:line 22", the default
> > behaivor after 'hardlockup' is to stay locked up rather than panic.
> 
> That actually says:
> 
>  A 'hardlockup' is defined as a bug that causes the CPU to loop in
>  kernel mode for more than 10 seconds (see "Implementation" below for 
>  details), without letting other interrupts have a chance to run.
>  Similarly to the softlockup case, the current stack trace is displayed
>  upon detection and the system will stay locked up unless the default
>  behavior is changed, which can be done through a sysctl,
>  'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC",
>  and a kernel parameter, "nmi_watchdog"
> 
> If your config has:
> 
>  CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
> 
> The kernel will panic on hard lockup by default unless you add nopanic.
> 
> If your config has:
> 
>  # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
> 
> Then the default will be not to panic unless you add "panic" to the
> kernel command line.
> 
> > 
> > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 2b8ee90..fcc9579 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2769,7 +2769,7 @@
> >  			0 - turn hardlockup detector in nmi_watchdog off
> >  			1 - turn hardlockup detector in nmi_watchdog on
> >  			When panic is specified, panic when an NMI watchdog
> > -			timeout occurs (or 'nopanic' to override the opposite
> > +			timeout occurs (or 'nopanic' which is the opposite
> >  			default). To disable both hard and soft lockup detectors,
> 
> Honestly, I think the original text states what it does better than
> your update. Because the nopanic is added to override the "opposite
> default" which is if the config was set to do so.
> 
> That said, this all still can be explained better. What about:
> 
>         nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
>                         Format: [panic,][nopanic,][num]
>                         Valid num: 0 or 1
>                         0 - turn hardlockup detector in nmi_watchdog off
>                         1 - turn hardlockup detector in nmi_watchdog on
>                         When panic is specified, panic when an NMI watchdog
>                         timeout occurs (or 'nopanic' to not panic on an NMI
> 			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
>                         To disable both hard and soft lockup detectors,
>                         please see 'nowatchdog'.
>                         This is useful when you use a panic=... timeout and
>                         need the box quickly up again.

Steven, your update makes it more clear to me. If patch is being written with
such update, here is my Reviewed-by:

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

thanks!

 - Joel

> 
> -- Steve
> 
> 
> >  			please see 'nowatchdog'.
> >  			This is useful when you use a panic=... timeout and
> 

Re: [PATCH 2/2] doc: kernel-parameters.txt: fix documentation of nmi_watchdog parameter

[Zhenzhong Duan]

Hi Steven,

On 2019/5/11 2:47, Steven Rostedt wrote:
> As nobody else commented, I will ;)
>
> Hi Zhenzhong!
>
> On Sun, 14 Apr 2019 11:11:04 +0800
> Zhenzhong Duan <zhenzhong.duan@oracle.com> wrote:
>
>> As stated in "Documentation/lockup-watchdogs.txt:line 22", the default
>> behaivor after 'hardlockup' is to stay locked up rather than panic.
> That actually says:
>
>   A 'hardlockup' is defined as a bug that causes the CPU to loop in
>   kernel mode for more than 10 seconds (see "Implementation" below for
>   details), without letting other interrupts have a chance to run.
>   Similarly to the softlockup case, the current stack trace is displayed
>   upon detection and the system will stay locked up unless the default
>   behavior is changed, which can be done through a sysctl,
>   'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC",
>   and a kernel parameter, "nmi_watchdog"
>
> If your config has:
>
>   CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
>
> The kernel will panic on hard lockup by default unless you add nopanic.
>
> If your config has:
>
>   # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
>
> Then the default will be not to panic unless you add "panic" to the
> kernel command line.
>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
>> ---
>>   Documentation/admin-guide/kernel-parameters.txt | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 2b8ee90..fcc9579 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -2769,7 +2769,7 @@
>>   			0 - turn hardlockup detector in nmi_watchdog off
>>   			1 - turn hardlockup detector in nmi_watchdog on
>>   			When panic is specified, panic when an NMI watchdog
>> -			timeout occurs (or 'nopanic' to override the opposite
>> +			timeout occurs (or 'nopanic' which is the opposite
>>   			default). To disable both hard and soft lockup detectors,
> Honestly, I think the original text states what it does better than
> your update. Because the nopanic is added to override the "opposite
> default" which is if the config was set to do so.
>
> That said, this all still can be explained better. What about:
>
>          nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
>                          Format: [panic,][nopanic,][num]
>                          Valid num: 0 or 1
>                          0 - turn hardlockup detector in nmi_watchdog off
>                          1 - turn hardlockup detector in nmi_watchdog on
>                          When panic is specified, panic when an NMI watchdog
>                          timeout occurs (or 'nopanic' to not panic on an NMI
> 			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
>                          To disable both hard and soft lockup detectors,
>                          please see 'nowatchdog'.
>                          This is useful when you use a panic=... timeout and
>                          need the box quickly up again.

Thanks Seeve for your comments, so the default behavior of hardlockup 
depends on the setting of CONFIG_BOOTPARAM_HARDLOCKUP_PANIC.

It did confused me previously. You suggested fix is better, I'll fix it 
later.


Zhenzhong

Re: [PATCH 1/2] doc: Fixup definition of rcupdate.rcu_task_stall_timeout

[Paul E. McKenney]

On Sun, Apr 14, 2019 at 11:11:03AM +0800, Zhenzhong Duan wrote:
> A positive value of rcupdate.rcu_task_stall_timeout is an interval
> in seconds rather than jiffies.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>

Good catch, applied, thank you!

Your other patch I must leave to others.

							Thanx, Paul

> ---
>  Documentation/RCU/stallwarn.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
> index 1ab70c3..13e88fc 100644
> --- a/Documentation/RCU/stallwarn.txt
> +++ b/Documentation/RCU/stallwarn.txt
> @@ -153,7 +153,7 @@ rcupdate.rcu_task_stall_timeout
>  	This boot/sysfs parameter controls the RCU-tasks stall warning
>  	interval.  A value of zero or less suppresses RCU-tasks stall
>  	warnings.  A positive value sets the stall-warning interval
> -	in jiffies.  An RCU-tasks stall warning starts with the line:
> +	in seconds.  An RCU-tasks stall warning starts with the line:
>  
>  		INFO: rcu_tasks detected stalls on tasks:
>  
> -- 
> 1.8.3.1
>