From: Rik van Riel <riel@surriel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
vschneid@redhat.com
Subject: Re: [PATCH 0/9] sched: make WARN_ON under rq->lock deadlock-safe (SCHED_WARN_ON)
Date: Thu, 11 Jun 2026 21:53:45 -0400 [thread overview]
Message-ID: <91b346ee1dfe88390acb462c9c1a8cb8dc3c2b05.camel@surriel.com> (raw)
In-Reply-To: <20260611191922.GK187714@noisy.programming.kicks-ass.net>
On Thu, 2026-06-11 at 21:19 +0200, Peter Zijlstra wrote:
>
> Myself, I almost exclusively run with earlycon serial and force
> printk
> to be early_printk() (effectively not using printk at all). This
> works
> perfectly fine and is the most reliable thing ever. I can push out
> characters to the UART from any context.
>
Great for development, not so good for production.
When something like an OOM kill happens, the amount
of data printed by the kernel can take a long time
to get flushed out a serial port.
In fact, it can take long enough to cause things
like RCU stalls and soft lockups, and break
workloads that way.
Having the serial console deferred allows those
systems to survive.
If the system crashes before the messages were sent
out the serial port, the dmesg buffer will be in
the vmcore, and get extracted by the crash analysis
tooling.
It sounds like the printk people may be right with
making that behavior an option, since different
scenarios require different behavior.
--
All Rights Reversed.
next prev parent reply other threads:[~2026-06-12 1:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-11 2:14 Rik van Riel
2026-06-11 2:14 ` [PATCH 1/9] sched: add SCHED_WARN_ON()/SCHED_WARN_ON_ONCE()/SCHED_WARN()/SCHED_WARN_ONCE() Rik van Riel
2026-06-11 2:14 ` [PATCH 2/9] sched/core: defer WARN console output under rq->lock Rik van Riel
2026-06-11 2:14 ` [PATCH 3/9] sched/fair: " Rik van Riel
2026-06-11 2:14 ` [PATCH 4/9] sched/deadline: " Rik van Riel
2026-06-11 2:14 ` [PATCH 5/9] sched/rt: " Rik van Riel
2026-06-11 2:14 ` [PATCH 6/9] sched_ext: " Rik van Riel
2026-06-11 2:14 ` [PATCH 7/9] sched/core_sched: " Rik van Riel
2026-06-11 2:14 ` [PATCH 8/9] sched/deadline: " Rik van Riel
2026-06-11 2:14 ` [PATCH 9/9] sched/rt: " Rik van Riel
2026-06-11 7:43 ` [PATCH 0/9] sched: make WARN_ON under rq->lock deadlock-safe (SCHED_WARN_ON) Peter Zijlstra
2026-06-11 16:20 ` Rik van Riel
2026-06-11 19:19 ` Peter Zijlstra
2026-06-12 1:53 ` Rik van Riel [this message]
2026-06-12 6:52 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=91b346ee1dfe88390acb462c9c1a8cb8dc3c2b05.camel@surriel.com \
--to=riel@surriel.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=kernel-team@meta.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®