Re: [PATCH v3 2/2] sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE

[Greg KH]

On Sun, Apr 10, 2022 at 12:42:24AM +0100, Qais Yousef wrote:
> +CC stable
> 
> On 01/20/22 16:25, Valentin Schneider wrote:
> > TASK_RTLOCK_WAIT currently isn't part of TASK_REPORT, thus a task blocking
> > on an rtlock will appear as having a task state == 0, IOW TASK_RUNNING.
> > 
> > The actual state is saved in p->saved_state, but reading it after reading
> > p->__state has a few issues:
> > o that could still be TASK_RUNNING in the case of e.g. rt_spin_lock
> > o ttwu_state_match() might have changed that to TASK_RUNNING
> > 
> > As pointed out by Eric, adding TASK_RTLOCK_WAIT to TASK_REPORT implies
> > exposing a new state to userspace tools which way not know what to do with
> > them. The only information that needs to be conveyed here is that a task is
> > waiting on an rt_mutex, which matches TASK_UNINTERRUPTIBLE - there's no
> > need for a new state.
> > 
> > Reported-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> 
> Any objection for this to be picked up by stable? We care about Patch 1 only in
> this series for stable, but it seems sensible to pick this one too, no strong
> feeling if it is omitted though.
> 
> AFAICT it seems the problem dates back since commit:
> 
> 	1593baab910d ("sched/debug: Implement consistent task-state printing")
> 
> or even before. I think v4.14+ is good enough.


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>