Re: [PATCH 0/3] Suppress undesirable hung task warnings.

[Peter Zijlstra]

On Mon, Sep 22, 2025 at 05:41:43PM +0800, Julian Sun wrote:
> As suggested by Andrew Morton in [1], we need a general mechanism 
> that allows the hung task detector to ignore unnecessary hung 
> tasks. This patch set implements this functionality.
> 
> Patch 1 introduces a PF_DONT_HUNG flag. The hung task detector will 
> ignores all tasks that have the PF_DONT_HUNG flag set.
> 
> Patch 2 introduces wait_event_no_hung() and wb_wait_for_completion_no_hung(), 
> which enable the hung task detector to ignore hung tasks caused by these
> wait events.
> 
> Patch 3 uses wb_wait_for_completion_no_hung() in the final phase of memcg 
> teardown to eliminate the hung task warning.
> 
> Julian Sun (3):
>   sched: Introduce a new flag PF_DONT_HUNG.
>   writeback: Introduce wb_wait_for_completion_no_hung().
>   memcg: Don't trigger hung task when memcg is releasing.

This is all quite terrible. I'm not at all sure why a task that is
genuinely not making progress and isn't killable should not be reported.