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 90D6726CE17; Mon, 12 Jan 2026 15:09:53 +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=1768230593; cv=none; b=HSNtC5UcL9zjeS96Zyrz1CXSursnEq5+uNsa+U53kyQUKTYfn4Xzja+AzfDTcKouHR1Npbe8+1L7uOmWmuYSm4OYpYq60YFEmi/oHB7KSLFB8Xj0uPM3EpNyuY5KafiIInkTM4cQ8bSNDet8sUnOO9t/Phfgai7ffV8HxyAYWSQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768230593; c=relaxed/simple; bh=SLLkOQ5pxC+Xfk84C/8GnkXcwep/asaQqw3bn0kNW0c=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=MvP1uZOHVM/bsd/IaUsFyrBJYXkTVdxHL6Q47iTdpbKDcqZPSYeaa6GkRVX7OgPeUNN3cnFpkDbu4D0fDd2VcOgXRzLGlHHP2co3k3qw0QEgVN6biTfhoEnbjmeUaWhSpWYatodt5Z9utj66L3UPdO1IgQqj07lfGB/QBwQS/nE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PoQG3MNb; 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="PoQG3MNb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D25EC16AAE; Mon, 12 Jan 2026 15:09:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768230593; bh=SLLkOQ5pxC+Xfk84C/8GnkXcwep/asaQqw3bn0kNW0c=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=PoQG3MNbzDflVzcD8PDZTq+p3TS6E4HKQMo/CnosiFbQgC6ToFRKjRh8W7BtW1j+/ F2KSeN0J1sO74fQ6WkQnw0BiRv8ROqBrIMdIVWheMozYjHI6Fe88+8sx/2B4fjbaEf qwwfikKji8Hb4ug0YcpLbYkxhd+xDKj4aQOIMDihcCD9TpwkHW+9v50MVZDVewZ8py tLJpx9mPsIE40lEtYy7JM+1OddpQsyjn+/uYdmku45XRrt1GqFs9NaqLWTwUAFxO1g MsR87UOq+cSoYZl4w4cqDqfrBLgz3QhzeiBzadvBXCglJC47OiLn7KCxgO1fpGac3d 8tVNRQMSYv0KA== From: Thomas Gleixner To: Waiman Long , Marc Zyngier Cc: Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH] irqchip/gic-v3-its: Don't acquire rt_spin_lock in allocate_vpe_l1_table() In-Reply-To: <40cec799-f363-4642-969b-24f5a2d56dfb@redhat.com> References: <20260107215353.75612-1-longman@redhat.com> <864iowmrx6.wl-maz@kernel.org> <87ms2nsqju.ffs@tglx> <86wm1qlq7l.wl-maz@kernel.org> <87ecnwij44.ffs@tglx> <86v7h8l9ht.wl-maz@kernel.org> <40cec799-f363-4642-969b-24f5a2d56dfb@redhat.com> Date: Mon, 12 Jan 2026 16:09:49 +0100 Message-ID: <87cy3eg94y.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 Sun, Jan 11 2026 at 18:02, Waiman Long wrote: > On 1/11/26 5:38 AM, Marc Zyngier wrote: >>> Also that patch seems to be incomplete because there is another >>> allocation further down in allocate_vpe_l1_table().... >> Yeah, I wondered why page allocation wasn't affected by this issue, >> but didn't try to find out. > > The use of GFP_ATOMIC flag in the page allocation request may help it to > dip into the reserved area and avoid taking any spinlock. In my own > test, just removing the kzalloc() call is enough to avoid any invalid > context warning. In the page allocation code, there is a zone lock and a > per_cpu_pages lock. They were not acquired in my particular test case, > though further investigation may be needed to make sure it is really safe. They might be acquired though. Only alloc_pages_nolock() guarantees that no lock is taken IIRC.