Re: [PATCH v2 4/5] workqueue: Show all busy workers in stall diagnostics

[Breno Leitao <leitao@debian.org>]

Hi Jiri,

On Thu, May 07, 2026 at 12:20:33PM +0200, Jiri Slaby wrote:
> On 05. 03. 26, 17:15, Breno Leitao wrote:
>
>   BUG: workqueue lockup - pool cpus=144 node=0 flags=0x4 nice=0 stuck for
> 168224s!

That's an extremely long stall (~1.95 days).

> ...
>   Showing busy workqueues and worker pools:
>   workqueue rcu_gp: flags=0x108
>     pwq 578: cpus=144 node=0 flags=0x4 nice=0 active=3 refcnt=4
> in:
>   https://bugzilla.suse.com/show_bug.cgi?id=1263947
> ?
>
> Can this (or other patch from the series) cause this? Should there be
> something like cpu_online() instead of task_is_running() somewhere?

This series only affects stall reporting, not detection. The changes run
after the watchdog has identified a stall, so the detection logic itself
remains unchanged.

To help diagnose this issue, could you provide some additional information:

1) Was CPU 144 online at any point? If so, when was it taken offline?
2) Does this message appear repeatedly? If you bring CPU 144 online, does
   the issue resolve?
3) Have you run similar tests on earlier kernel versions without seeing
   this behavior, or is this a clear regression?


Thanks for the report,
--breno