* [PATCH] printk: Don't WARN on kthread_run failure.
@ 2026-08-04 13:52 Tetsuo Handa
2026-08-20 9:52 ` John Ogness
2026-08-20 13:17 ` Petr Mladek
0 siblings, 2 replies; 3+ messages in thread
From: Tetsuo Handa @ 2026-08-04 13:52 UTC (permalink / raw)
To: Petr Mladek, Steven Rostedt, John Ogness, Sergey Senozhatsky,
Thomas Gleixner, LKML
Since __kthread_create_on_node() returns -EINTR upon SIGKILL,
we should not use WARN_ON() in order to catch kthread_run() failure.
Reported-by: syzbot+1ebbc20f223b99446034@syzkaller.appspotmail.com
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@I-love.SAKURA.ne.jp>
---
kernel/printk/nbcon.c | 2 +-
kernel/printk/printk.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 4b03b019cd5e..a5921a84a80e 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1382,7 +1382,7 @@ bool nbcon_kthread_create(struct console *con)
return true;
kt = kthread_run(nbcon_kthread_func, con, "pr/%s%d", con->name, con->index);
- if (WARN_ON(IS_ERR(kt))) {
+ if (IS_ERR(kt)) {
con_printk(KERN_ERR, con, "failed to start printing thread\n");
return false;
}
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2fe9a963c823..cf15ed75fd26 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3725,7 +3725,7 @@ static bool legacy_kthread_create(void)
lockdep_assert_console_list_lock_held();
kt = kthread_run(legacy_kthread_func, NULL, "pr/legacy");
- if (WARN_ON(IS_ERR(kt))) {
+ if (IS_ERR(kt)) {
pr_err("failed to start legacy printing thread\n");
return false;
}
--
2.52.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] printk: Don't WARN on kthread_run failure.
2026-08-04 13:52 [PATCH] printk: Don't WARN on kthread_run failure Tetsuo Handa
@ 2026-08-20 9:52 ` John Ogness
2026-08-20 13:17 ` Petr Mladek
1 sibling, 0 replies; 3+ messages in thread
From: John Ogness @ 2026-08-20 9:52 UTC (permalink / raw)
To: Tetsuo Handa, Petr Mladek, Steven Rostedt, Sergey Senozhatsky,
Thomas Gleixner, LKML
On 2026-08-04, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> 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@syzkaller.appspotmail.com
> 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@I-love.SAKURA.ne.jp>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
[0] https://lore.kernel.org/lkml/87ed95j8yh.fsf@jogness.linutronix.de
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] printk: Don't WARN on kthread_run failure.
2026-08-04 13:52 [PATCH] printk: Don't WARN on kthread_run failure Tetsuo Handa
2026-08-20 9:52 ` John Ogness
@ 2026-08-20 13:17 ` Petr Mladek
1 sibling, 0 replies; 3+ messages in thread
From: Petr Mladek @ 2026-08-20 13:17 UTC (permalink / raw)
To: Tetsuo Handa
Cc: Steven Rostedt, John Ogness, Sergey Senozhatsky, Thomas Gleixner,
LKML
On Tue 2026-08-04 22:52:19, Tetsuo Handa wrote:
> Since __kthread_create_on_node() returns -EINTR upon SIGKILL,
> we should not use WARN_ON() in order to catch kthread_run() failure.
>
> Reported-by: syzbot+1ebbc20f223b99446034@syzkaller.appspotmail.com
> 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@I-love.SAKURA.ne.jp>
Makes sense.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Best Regards,
Petr
PS: We are in the middle of the merge window. I am going to
push this into printk tree on top of the pending merge
request once it gets accepted.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-08-20 13:17 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-08-04 13:52 [PATCH] printk: Don't WARN on kthread_run failure Tetsuo Handa
2026-08-20 9:52 ` John Ogness
2026-08-20 13:17 ` Petr Mladek
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.