From: John Ogness <john.ogness@linutronix.de>
To: Breno Leitao <leitao@debian.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Marco Elver <elver@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Vlastimil Babka <vbabka@kernel.org>,
Petr Mladek <pmladek@suse.com>,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com,
Breno Leitao <leitao@debian.org>,
Toshiyuki Sato <fj6611ie@aa.jp.fujitsu.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] stackdepot: don't WARN when the depot runs out of pools
Date: Wed, 04 Nov 2026 09:26:55 +0106 [thread overview]
Message-ID: <87wlqtxb14.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <20261103-stackdepot-full-warn-v1-1-41f1fc651b64@debian.org>
On 2026-11-03, Breno Leitao <leitao@debian.org> wrote:
> That deferral only applies to legacy consoles. ON nbcon WARN() puts the
> CPU in emergency mode, and in emergency mode printk() flushes all
> pending records to the nbcon consoles from the calling context.
Yes. WARN() is supposed to be for critical issues.
> With
> a slow serial console (pl011 is an nbcon console) and a backlog of
> messages, that flush can outlast the hard lockup threshold, all of it
> with pool_lock held and IRQs disabled, while every other CPU that needs
> to save a new stack trace spins on pool_lock.
Several serial drivers call touch_nmi_watchdog() (such as 8250) to avoid
this issue. Perhaps the pl011 should be doing this as well (at least for
the write_atomic() path)?
> Running out of depot space is an expected condition under heavy debug
> load, not a kernel bug, so report it with pr_warn_once() instead.
This is the key takeaway. WARN() is not appropriate here.
Reviewed-by: John Ogness <john.ogness@linutronix.de>
next prev parent reply other threads:[~2026-11-04 8:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-03 11:01 Breno Leitao
2026-11-03 12:19 ` Marco Elver
2026-11-04 8:20 ` John Ogness [this message]
2026-11-04 9:19 ` Petr Mladek
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