linux-kernel - Re: [linus:master] [mm/vmalloc] a061578043: BUG:spinlock_trylock_failure_on_UP_on

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Message-ID: <aUXhy1Jyv7_GccIp@casper.infradead.org>
Date: Fri, 19 Dec 2025 23:37:47 +0000
From: Matthew Wilcox <willy@...radead.org>
To: kernel test robot <oliver.sang@...el.com>
Cc: Vishal Moola <vishal.moola@...il.com>, oe-lkp@...ts.linux.dev,
	lkp@...el.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Uladzislau Rezki <urezki@...il.com>, linux-mm@...ck.org,
	Mel Gorman <mgorman@...hsingularity.net>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [linus:master] [mm/vmalloc]  a061578043:
 BUG:spinlock_trylock_failure_on_UP_on_CPU

On Fri, Dec 19, 2025 at 08:26:14PM +0000, Matthew Wilcox wrote:
> Now, as I recall, we are very much doing this on purpose.  We decided
> not to disable interrupts at this point for improved interrupt
> latency, accepting the possibility that we'd occasionally fail
> the trylock.  Except on UP that's now an assertion failure.

This is stupid and wrong.  If we have CONFIG_SMP=n and
CONFIG_DEBUG_SPINLOCK=n, then trylock always succeeds.  And we'll end
up corrupting the data structure protected by the lock.  So the warning
is real, and we need to fix this.

With my distro hat on, I do not give two hoots.  We don't ship a nosmp
kernel.  I suspect all other distros (except maybe something targetting
m68k?) are in the same boat.