Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung on mutex

[Waiman Long <llong@redhat.com>]

On 2/19/25 9:08 PM, Masami Hiramatsu (Google) wrote:
> On Wed, 19 Feb 2025 18:58:10 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> On Thu, 20 Feb 2025 08:09:08 +0900
>> Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
>>
>>> So something like this?
>>>
>>> unsigned int	block_flags;
>>> union {
>>> 	struct mutex	*mutex;
>>> 	struct rwsem	+rwsem;
>>> 	struct rtmutex	*rtmutex;
>>> } blocked_on;
>>>
>>> enum {
>>> 	BLOCKED_ON_MUTEX;
>>> 	BLOCKED_ON_RWSEM;
>>> 	BLOCKED_ON_RTMUTEX;
>>> 	BLOCKED_ON_IO;
>>> } block_reason;
>>>
>>> For the safety, we may anyway lock the task anyway, but that is the
>>> same as stacktrace.
>> Why not make it into a single entity?
>>
>> struct blocked_on {
>> 	unsigned int	flags;
>> 	union {
>> 		struct mutex	*mutex;
>> 		struct rwsem	*rwsem;
>> 		struct rtmutex	*rtmutex;
>> 	} blocked_on;
>> };
> Yes, and we also merge current mutex_waiter too.

I don't think we should merge mutex_waiter as it contains additional 
fields that are not useful to others. We don't want enlarge the size of 
task_struct unnecessarily.

Cheers,
Longman