From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 111643B8940 for ; Wed, 11 Mar 2026 07:56:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773215801; cv=none; b=KxJoWC1BYIaMS9qAnTGwaTpm2IwLPT0eMMV5IS8xIZzkXbe6TzJutJJWj5JNwNwZSGBrndLqdCg4bFttscSaAPYmbOoxWXFmez2+KjsAwpwn8IkBvlYWVKt26hvdUNt3vq+b6jzbQqNZRKmCihlQS5FyS6dVT7kQyZUstOl5EX4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773215801; c=relaxed/simple; bh=fcvksonGw03s2e99v+rQSRE4+Oj7GZWhbhUpm91Wl3Y=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=jHyIIY/6tBlz4hFHO3wBkO4mCUuQbZdzy7Zpio8b7/51pICa0WEmuMH2Mha98WxxDS+3dmEMWDvXbl9MJyrbZQ3qXt/jtlPffsXhShUVgHN+swjadmNZHOaoimAOWHSW+91goSJD7F7839QWT6Pkcq52V8jrxIEoRWPORsGZi4M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H68RJjH5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="H68RJjH5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B2EDEC2BC9E; Wed, 11 Mar 2026 07:56:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773215800; bh=fcvksonGw03s2e99v+rQSRE4+Oj7GZWhbhUpm91Wl3Y=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=H68RJjH5H4tnmA81EgPIj2vANAZ7cc3Ii8UV2w/PWkwuse11HfDFnEb0jq+kAcTth RkFVHLqoWjc4vbAVVjaEkGl+n4fNF3q0df9PJ+UgCOLD5wxHsCL9KRy71ozj54Phpk wi1fg1V57MTJUoHVezlS/znZJjQJAhnsWUzpsq1IFUWY9xXTOQLo2l2DhKUjRRbeh9 5U6zQFHjw0A5tBwsDbOt3ZJajF1fyonkfi0XdSIQXyQBwg6fN4f0ZL41vSVmzo91on +fiq4XeIBsldaxG6BlPRrGjwpteeecVIJowWSgiv/EkKqmsNfoB9lJHfBo2JYmPvuC PAXBWbO+6eekQ== From: Thomas Gleixner To: syzbot , linux-kernel@vger.kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com Cc: Steffen Klassert , Daniel Jordan Subject: Re: [syzbot] [kernel?] WARNING in _cpu_down In-Reply-To: <69af0a05.050a0220.310d8.002f.GAE@google.com> References: <69af0a05.050a0220.310d8.002f.GAE@google.com> Date: Wed, 11 Mar 2026 08:56:36 +0100 Message-ID: <87sea6re8b.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, Mar 09 2026 at 10:57, syzbot wrote: > syzbot found the following issue on: > > HEAD commit: 4ae12d8bd9a8 Merge tag 'kbuild-fixes-7.0-2' of git://git.k.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=177cca02580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=163cf0fb07ea84d3 > dashboard link: https://syzkaller.appspot.com/bug?extid=123e1b70473ce213f3af > compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 > smpboot: CPU 1 is now offline > smpboot: Booting Node 0 Processor 1 APIC 0x1 > ------------[ cut here ]------------ > DEAD callback error for CPU1 > WARNING: kernel/cpu.c:1463 at _cpu_down+0x759/0x1020 kernel/cpu.c:1463, CPU#0: syz.0.1960/14614 That means one of the hotplug state callbacks which are issued after a CPU is dead returned an error. That's wrong. Those callbacks are not supposed to fail as there is no way to rollback at that point. A quick coccinelle search finds exactly one callback in that stage which might return an error code: padata_cpu_dead() Not sure how to fix that. I leave it to the padata folks ... Thanks tglx