Re: [PATCH] printk: Don't WARN on kthread_run failure.

[John Ogness]

On 2026-08-04, Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:

> Since __kthread_create_on_node() returns -EINTR upon SIGKILL,
> we should not use WARN_ON() in order to catch kthread_run() failure.

For historical context, the WARN_ON() was suggested here [0].

But since a kthread_run() failure also prints a dedicated failure
message, the WARN_ON is overkill.

> Reported-by: syzbot+1ebbc20f223b99446034@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=1ebbc20f223b99446034
> Fixes: 5f53ca3ff83b ("printk: Implement legacy printer kthread for PREEMPT_RT")
> Fixes: 76f258bf3f2a ("printk: nbcon: Introduce printer kthreads")
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

Reviewed-by: John Ogness <john.ogness@xxxxxxxxxxxxx>

[0] https://lore.kernel.org/lkml/87ed95j8yh.fsf@xxxxxxxxxxxxxxxxxxxxx