From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A8126332EC5 for ; Fri, 21 Aug 2026 01:20:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787275245; cv=none; b=KD8TMT4rqA1wbOHmDDlTa7FFiZGJgiI5ZBg6wmPusCQaxzNB+9yIYYO91IO85ypPTqLnrx/rSvyqV1sIbymUrT93YpyG0yDrnqSl3d4h1TN3/brULIFuJtCHV3cP66FWXKz5npcNI6k4pTt8vRdMvnISiK6ZlWS3QIKep1dBh4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787275245; c=relaxed/simple; bh=SNN2p2Qd7Yf1s7jAgSIRlMNVEzR9zJwSaNChHjycvDg=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=rnK3ErTQmiL1fUPpv2fcGo9DMHNU0zIppBHfj4K55d8Yn5nSpUBuGWhuIS2xsvdPj6Bu/S9kEQdTV6sOnB3M/Un4cUiJvgxpAuR13HE49zayt4s4wf5Y62U8HZ9syfFFw0omTsEys2QzuUbDrAvP710+tNsBtpHrtufWhx+joPM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=RNNV+cYZ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="RNNV+cYZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11ECB1F000E9; Fri, 21 Aug 2026 01:20:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787275239; bh=hfFyCgIVsZNfHPslBJGjBS2F3LWrEzkMWOBp11fXAF0=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=RNNV+cYZ5+aJda8P1sCv52PVqhOWoeLyirlvjLUKSUBqZOYAefQ/InbP9RhJaxp2+ iONedHR86FeYZsi0Ko0TyghBWfBrb5ZrVxVqnTL+/nF5ZvYgF0X3MqeYE03sZsDKb3 6Zzb6TLk5b2bSbnTKSPP+yG4YLX/t2vlFNWeNifc= Date: Thu, 20 Aug 2026 18:20:38 -0700 From: Andrew Morton To: Ye Liu Cc: syzbot , brendan.jackman@linux.dev, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, surenb@google.com, syzkaller-bugs@googlegroups.com, vbabka@kernel.org, ziy@nvidia.com, Zhen Ni , Oscar Salvador , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in kvm_vm_release (4) Message-Id: <20260820182038.c45e454506c8cd3c1f21930b@linux-foundation.org> In-Reply-To: References: <6a86fe29.f7a79266.2f965f.004a.GAE@google.com> <20260820092904.7a2b43fff85ed0c13b9c74ab@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 21 Aug 2026 09:06:48 +0800 Ye Liu wrote: > > : The combination of debug tools: KASAN quarantine processing + ORC > > : unwinder + page_owner stack tracing executed so slowly on the CPU that > > : it exceeded the RCU stall threshold. > > > > (I think we've recently seen the same thing, different callers) > > > > I can't say I'm terribly motivated. page_owner is expensive and if you > > run heavy stress testing with page_owner enabled then such things > > aren't surprising. > > > > Let me Cc a few page_owner and KASAN people, see if they feel > > differently. > > Adding cond_resched() to the qlist_free_all() loop would fix this . > kasan_quarantine_remove_cache() already dose the same in its scanning loop. I don't think cond_resched() does what we want for RCU stalls. And cond_resched() is a no-op without CONFIG_PREEMPT_NONE, which wasn't set here.