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 X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F829C04EBD for ; Tue, 16 Oct 2018 04:16:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 540B3214AB for ; Tue, 16 Oct 2018 04:16:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="JlmA7YSv"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="ber74H4A" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 540B3214AB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730092AbeJPMEb (ORCPT ); Tue, 16 Oct 2018 08:04:31 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:39630 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728480AbeJPMEa (ORCPT ); Tue, 16 Oct 2018 08:04:30 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 7978661364; Tue, 16 Oct 2018 04:16:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1539663366; bh=XD6yAbdKU+W1gaQrsNMVMdA7e/vMB9VIT5n8m0qce0M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JlmA7YSvbTGolKZ1RxPHC9MCo9L3VcMn08TDDbHn+og6BmGA0NWzKik7dy8E/3EE0 A2nFJKxcv1k8PB2/1INM59O7t7Y2PBZ2dy9zoe6JsbkLBdTUmUVu6ezGubNb0yayIn sMp4Sm15W03JutymQ4uoZ0mxKqu/84zenEcOroWI= Received: from codeaurora.org (blr-c-bdr-fw-01_globalnat_allzones-outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: pkondeti@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 4113061472; Tue, 16 Oct 2018 04:15:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1539663359; bh=XD6yAbdKU+W1gaQrsNMVMdA7e/vMB9VIT5n8m0qce0M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ber74H4A7h/2w9dh/yU/Rb2DgcNgFzsYNAJeXNu8s7uH3HGJZqgfpUslJJn4tLzVs N0QRzAv3xGMiuRVW2d1o56qPhn842AZe/t4TDlamK1Opp6CB+EPOhccNGSnzCgL31H Z3PjGE8C4uf8+vmHiuTYvmoI+nJYD5Kgr2gnM9KI= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 4113061472 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=pkondeti@codeaurora.org Date: Tue, 16 Oct 2018 09:45:52 +0530 From: Pavan Kondeti To: Frederic Weisbecker Cc: LKML , Frederic Weisbecker , Sebastian Andrzej Siewior , Peter Zijlstra , "David S . Miller" , Linus Torvalds , Thomas Gleixner , "Paul E . McKenney" , Ingo Molnar , Mauro Carvalho Chehab Subject: Re: [RFC PATCH 29/30] softirq: Make softirq processing softinterruptible Message-ID: <20181016041552.GA27587@codeaurora.org> References: <1539213137-13953-1-git-send-email-frederic@kernel.org> <1539213137-13953-30-git-send-email-frederic@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1539213137-13953-30-git-send-email-frederic@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Frederic, On Thu, Oct 11, 2018 at 01:12:16AM +0200, Frederic Weisbecker wrote: > From: Frederic Weisbecker > > Make do_softirq() re-entrant and allow a vector, being either processed > or disabled, to be interrupted by another vector. This way a vector > won't be able to monopolize the CPU for a long while at the expense of > the others that may rely on some predictable latency, especially on > softirq disabled sections that used to disable all vectors. > I understand that a long running softirq can be preempted/interrupted by other softirqs which is not possible today. I have few questions on your patches. (1) When softirq processing is pushed to ksoftirqd, then the long running softirq can still block other softirqs (not in SOFTIRQ_NOW_MASK) for a while. correct? (2) When softirqs processing happens asynchronously, a particular softirq like TASKLET can keep interrupting an already running softirq like TIMER/NET_RX, correct? In worse case scenario, a long running softirq like NET_RX interrupt a TIMER softirq. But I guess this is something expected with this. i.e each softirq is independent and whichever comes recent gets to interrupt the previously running softirqs. Thanks, Pavan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.