[PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[Jun Miao]

It's "mustn't", not "musn't". Let's fix that.

Signed-off-by: Jun Miao <jun.miao@windriver.com>
---
 kernel/hung_task.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 9888e2bc8c76..ea5ba912db06 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 	/*
 	 * When a freshly created task is scheduled once, changes its state to
 	 * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
-	 * musn't be checked.
+	 * mustn't be checked.
 	 */
 	if (unlikely(!switch_count))
 		return;
-- 
2.32.0

Re: [PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[Daniel Bristot de Oliveira]

On 8/6/21 1:40 PM, Jun Miao wrote:

> It's "mustn't", not "musn't". Let's fix that.
> 
> Signed-off-by: Jun Miao <jun.miao@windriver.com>

Reviewed-by: Daniel Bristot de Oliveira <bristot@kernel.org>

-- Daniel
> ---
>  kernel/hung_task.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 9888e2bc8c76..ea5ba912db06 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
>  	/*
>  	 * When a freshly created task is scheduled once, changes its state to
>  	 * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
> -	 * musn't be checked.
> +	 * mustn't be checked.
>  	 */
>  	if (unlikely(!switch_count))
>  		return;
> 

Re: [PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[Lukas Bulwahn]

On Fri, Aug 6, 2021 at 1:41 PM Jun Miao <jun.miao@windriver.com> wrote:
>
> It's "mustn't", not "musn't". Let's fix that.
>
> Signed-off-by: Jun Miao <jun.miao@windriver.com>
> ---
>  kernel/hung_task.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 9888e2bc8c76..ea5ba912db06 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
>         /*
>          * When a freshly created task is scheduled once, changes its state to
>          * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
> -        * musn't be checked.
> +        * mustn't be checked.

I cannot even parse this comment.

Does "When a freshly created task is scheduled once, changes its state
to TASK_UNINTERRUPTIBLE" mean "When a freshly created task is
scheduled once and it changes its state to TASK_UNINTERRUPTIBLE"?

Does this "it must not be checked" read as "it shall not be checked"
(as in "because if you check it, something goes wrong") or "it is not
required to be checked" (as in "usually, you need to check it
(otherwise something goes wrong), but here in this case, you do not
need to check it, because it cannot go wrong in this case")?

Fixing spelling mistakes is okay, but it is even better to check the
sentence you are correcting and try to comprehend it.

Lukas

Re: [PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[Jun Miao]

On 8/6/21 10:27 PM, Lukas Bulwahn wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Fri, Aug 6, 2021 at 1:41 PM Jun Miao <jun.miao@windriver.com> wrote:
>> It's "mustn't", not "musn't". Let's fix that.
>>
>> Signed-off-by: Jun Miao <jun.miao@windriver.com>
>> ---
>>   kernel/hung_task.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
>> index 9888e2bc8c76..ea5ba912db06 100644
>> --- a/kernel/hung_task.c
>> +++ b/kernel/hung_task.c
>> @@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
>>          /*
>>           * When a freshly created task is scheduled once, changes its state to
>>           * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
>> -        * musn't be checked.
>> +        * mustn't be checked.
> I cannot even parse this comment.
>
> Does "When a freshly created task is scheduled once, changes its state
> to TASK_UNINTERRUPTIBLE" mean "When a freshly created task is
> scheduled once and it changes its state to TASK_UNINTERRUPTIBLE"?
>
> Does this "it must not be checked" read as "it shall not be checked"
> (as in "because if you check it, something goes wrong") or "it is not
> required to be checked" (as in "usually, you need to check it
> (otherwise something goes wrong), but here in this case, you do not
> need to check it, because it cannot go wrong in this case")?
>
> Fixing spelling mistakes is okay, but it is even better to check the
> sentence you are correcting and try to comprehend it.

Hi Lukas, thanks for your advice from my heart.

 From the context of code:
---
  90         unsigned long switch_count = t->nvcsw + t->nivcsw;
  91
  ... ...
  99         /*
100          * When a freshly created task is scheduled once, changes 
its state to
101          * TASK_UNINTERRUPTIBLE without having ever been switched 
out once, it
102          * mustn't be checked.
103          */
104         if (unlikely(!switch_count))
105                 return;
---

It should read as "it shall not be checked" (as in "because if you check 
it, something goes wrong")
. When create a task and set it as "TASK_UNINTERRUPTIBLE" we don`t need 
to check "swtich_count=0".
If check will report a false positive.

 From a history commit cf2592f59c0e, there is a detail explain:
     - the task is freshly created and scheduled
     - it puts its state to TASK_UNINTERRUPTIBLE and is not yet switched out
     - check_hung_task() scans this task and will report a false 
positive because
       t->nvcsw + t->nivcsw == t->last_switch_count == 0

     Add a check for such cases.

Thanks
Jun
> Lukas

Re: [PATCH] kernel/hung_task.c: Fix a typo in check_hung_task() comment

[Jun Miao]

Hi,

     What about this spelling mistakes ?

Thanks
Jun


On 8/7/21 8:21 PM, Jun Miao wrote:
>
> On 8/6/21 10:27 PM, Lukas Bulwahn wrote:
>> [Please note: This e-mail is from an EXTERNAL e-mail address]
>>
>> On Fri, Aug 6, 2021 at 1:41 PM Jun Miao <jun.miao@windriver.com> wrote:
>>> It's "mustn't", not "musn't". Let's fix that.
>>>
>>> Signed-off-by: Jun Miao <jun.miao@windriver.com>
>>> ---
>>>   kernel/hung_task.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
>>> index 9888e2bc8c76..ea5ba912db06 100644
>>> --- a/kernel/hung_task.c
>>> +++ b/kernel/hung_task.c
>>> @@ -99,7 +99,7 @@ static void check_hung_task(struct task_struct *t, 
>>> unsigned long timeout)
>>>          /*
>>>           * When a freshly created task is scheduled once, changes 
>>> its state to
>>>           * TASK_UNINTERRUPTIBLE without having ever been switched 
>>> out once, it
>>> -        * musn't be checked.
>>> +        * mustn't be checked.
>> I cannot even parse this comment.
>>
>> Does "When a freshly created task is scheduled once, changes its state
>> to TASK_UNINTERRUPTIBLE" mean "When a freshly created task is
>> scheduled once and it changes its state to TASK_UNINTERRUPTIBLE"?
>>
>> Does this "it must not be checked" read as "it shall not be checked"
>> (as in "because if you check it, something goes wrong") or "it is not
>> required to be checked" (as in "usually, you need to check it
>> (otherwise something goes wrong), but here in this case, you do not
>> need to check it, because it cannot go wrong in this case")?
>>
>> Fixing spelling mistakes is okay, but it is even better to check the
>> sentence you are correcting and try to comprehend it.
>
> Hi Lukas, thanks for your advice from my heart.
>
> From the context of code:
> ---
>  90         unsigned long switch_count = t->nvcsw + t->nivcsw;
>  91
>  ... ...
>  99         /*
> 100          * When a freshly created task is scheduled once, changes 
> its state to
> 101          * TASK_UNINTERRUPTIBLE without having ever been switched 
> out once, it
> 102          * mustn't be checked.
> 103          */
> 104         if (unlikely(!switch_count))
> 105                 return;
> ---
>
> It should read as "it shall not be checked" (as in "because if you 
> check it, something goes wrong")
> . When create a task and set it as "TASK_UNINTERRUPTIBLE" we don`t 
> need to check "swtich_count=0".
> If check will report a false positive.
>
> From a history commit cf2592f59c0e, there is a detail explain:
>     - the task is freshly created and scheduled
>     - it puts its state to TASK_UNINTERRUPTIBLE and is not yet 
> switched out
>     - check_hung_task() scans this task and will report a false 
> positive because
>       t->nvcsw + t->nivcsw == t->last_switch_count == 0
>
>     Add a check for such cases.
>
> Thanks
> Jun
>> Lukas