hung_task: Add detection count to hung task warning message

[PATCH v2] hung_task: Add detection count to hung task warning message

Posted by Ye Liu 2 months, 1 week ago

From: Ye Liu <liuye@kylinos.cn>

Add [#N] to hung task warnings to show occurrence count.
This helps quickly identify warning order when multiple
messages appear in logs.

Signed-off-by: Ye Liu <liuye@kylinos.cn>

Changes in v2:
- Directly use sysctl_hung_task_detect_count.
- Link to v1:https://lore.kernel.org/all/20250721031755.1418556-1-ye.liu@linux.dev/
---
 kernel/hung_task.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 8708a1205f82..231afdb68bb2 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -232,8 +232,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 	if (sysctl_hung_task_warnings || hung_task_call_panic) {
 		if (sysctl_hung_task_warnings > 0)
 			sysctl_hung_task_warnings--;
-		pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
-		       t->comm, t->pid, (jiffies - t->last_switch_time) / HZ);
+		pr_err("INFO: task %s:%d blocked for more than %ld seconds. [#%ld]\n",
+		       t->comm, t->pid, (jiffies - t->last_switch_time) / HZ,
+		       sysctl_hung_task_detect_count);
 		pr_err("      %s %s %.*s\n",
 			print_tainted(), init_utsname()->release,
 			(int)strcspn(init_utsname()->version, " "),
-- 
2.43.0

Re: [PATCH v2] hung_task: Add detection count to hung task warning message

Posted by Lance Yang 2 months, 1 week ago


On 2025/7/24 15:23, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
> 
> Add [#N] to hung task warnings to show occurrence count.
> This helps quickly identify warning order when multiple
> messages appear in logs.

Hmm... once we have this number, what do we do with it?

While I totally get the desire for a quick reference number, my thinking
is that the hung_task_detect_count counter is the intended and more
reliable way for users to check.

But like I said before, let's see what Andrew thinks ;)

Thanks,
Lance

> 
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> 
> Changes in v2:
> - Directly use sysctl_hung_task_detect_count.
> - Link to v1:https://lore.kernel.org/all/20250721031755.1418556-1-ye.liu@linux.dev/
> ---
>   kernel/hung_task.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 8708a1205f82..231afdb68bb2 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -232,8 +232,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
>   	if (sysctl_hung_task_warnings || hung_task_call_panic) {
>   		if (sysctl_hung_task_warnings > 0)
>   			sysctl_hung_task_warnings--;
> -		pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
> -		       t->comm, t->pid, (jiffies - t->last_switch_time) / HZ);
> +		pr_err("INFO: task %s:%d blocked for more than %ld seconds. [#%ld]\n",
> +		       t->comm, t->pid, (jiffies - t->last_switch_time) / HZ,
> +		       sysctl_hung_task_detect_count);
>   		pr_err("      %s %s %.*s\n",
>   			print_tainted(), init_utsname()->release,
>   			(int)strcspn(init_utsname()->version, " "),

Re: [PATCH v2] hung_task: Add detection count to hung task warning message

Posted by Andrew Morton 2 months, 1 week ago

On Thu, 24 Jul 2025 20:06:52 +0800 Lance Yang <lance.yang@linux.dev> wrote:

> 
> 
> On 2025/7/24 15:23, Ye Liu wrote:
> > From: Ye Liu <liuye@kylinos.cn>
> > 
> > Add [#N] to hung task warnings to show occurrence count.
> > This helps quickly identify warning order when multiple
> > messages appear in logs.
> 
> Hmm... once we have this number, what do we do with it?

Yes, adding to the changelog a more comprehensive description of the
use-cases would help get this patch into Linux.

> While I totally get the desire for a quick reference number, my thinking
> is that the hung_task_detect_count counter is the intended and more
> reliable way for users to check.

But that's what this patch does?  Confused.

> But like I said before, let's see what Andrew thinks ;)

Andrew thinks it's a pain when the title of a patch is changed! 
Fortunately the changelog had a "Link to v1".

Re: [PATCH v2] hung_task: Add detection count to hung task warning message

Posted by Lance Yang 2 months, 1 week ago


On 2025/7/25 06:10, Andrew Morton wrote:
> On Thu, 24 Jul 2025 20:06:52 +0800 Lance Yang <lance.yang@linux.dev> wrote:
> 
>>
>>
>> On 2025/7/24 15:23, Ye Liu wrote:
>>> From: Ye Liu <liuye@kylinos.cn>
>>>
>>> Add [#N] to hung task warnings to show occurrence count.
>>> This helps quickly identify warning order when multiple
>>> messages appear in logs.
>>
>> Hmm... once we have this number, what do we do with it?
> 
> Yes, adding to the changelog a more comprehensive description of the
> use-cases would help get this patch into Linux.

Yep, exactly. Please sell this change to us! A good changelog should
explain not just what the patch does, but why it's necessary ;p

> 
>> While I totally get the desire for a quick reference number, my thinking
>> is that the hung_task_detect_count counter is the intended and more
>> reliable way for users to check.
> 
> But that's what this patch does?  Confused.

I'm just not sure if this quick reference number is something users
actually need, as there doesn't seem to be a strong use-case for it yet.

My point was that actively checking the sysctl is the proper way to get the
total count. But of course, if users genuinely need this inline number, I
have no objection ;)

> 
>> But like I said before, let's see what Andrew thinks ;)
> 
> Andrew thinks it's a pain when the title of a patch is changed!
> Fortunately the changelog had a "Link to v1".

https://lore.kernel.org/lkml/20250721031755.1418556-1-ye.liu@linux.dev/

Thanks,
Lance