From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 576D9C77B73 for ; Thu, 27 Apr 2023 10:07:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243472AbjD0KHF (ORCPT ); Thu, 27 Apr 2023 06:07:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243429AbjD0KHE (ORCPT ); Thu, 27 Apr 2023 06:07:04 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B6D11FC0; Thu, 27 Apr 2023 03:07:03 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 21610633E7; Thu, 27 Apr 2023 10:07:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDF70C433EF; Thu, 27 Apr 2023 10:07:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1682590022; bh=NpPUxdiGmbPhMzPhGolYoqA+iiu2qAbTIUmG3IlvkBg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uopaMlnxAadrlJeOvUyXERVtGXrAzEIpeMldv/tk06iMcNE7F3/hWfRj+Ca/EUtXb YdUsi6lCe8viviR8eAZm5/Mnv2f3WZ1wmXnrniXiesePc/22nBQmZe6vdlGPiPjsH1 jZssnpP9l4KgpFNHBQeeMoM6ebmwHpWYxqoDMsDOgYwByzaBkJALj6i+dGbH2Inby6 pgWeOqazPR8GxI6JJUoI64n6zcMvKDj9OajMirX+Bb3VrtSvPa5zWdkv1PY/PKjulx 7nNWEq7qTf2PJpukuqRlk21euEUCxN1l/ctfm6C/5c2AhQJqLMSS6gvez1G09U6EMk j8aceljwHzt7A== Date: Thu, 27 Apr 2023 11:06:57 +0100 From: Will Deacon To: "Bouska, Zdenek" Cc: Thomas Gleixner , Catalin Marinas , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Kiszka, Jan" , "linux-rt-users@vger.kernel.org" , Nishanth Menon , Puranjay Mohan Subject: Re: Unfair qspinlocks on ARM64 without LSE atomics => 3ms delay in interrupt handling Message-ID: <20230427100656.GA10855@willie-the-truck> References: <87pm7qxrg6.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Thu, Apr 27, 2023 at 09:38:59AM +0000, Bouska, Zdenek wrote: > > Why is this interrupt handling specific? Just because it's the place > > where you observed it? > Yes. > > > So if that helps, then this needs to be addressed globaly and not with > > some crude hack in the interrupt handling code. > I just wrote, what helps for me. I didn't mean it as a proposal for merge. > Sorry for confusion. > > I tried using Will's cpu_relax() implementation [1] everywhere but I was not > successful with that yet. ARM64's VDSO makes it complicating and even > if I left original cpu_relax() just in VDSO, Linux did not boot for me. It definitely seemed to work when I posted it all those years ago, but I'm not surprised if it needs some TLC to revive it on more recent kernels. Will