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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 AD7FDC4338F for ; Thu, 12 Aug 2021 11:17:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 483CC6109D for ; Thu, 12 Aug 2021 11:17:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236781AbhHLLSG (ORCPT ); Thu, 12 Aug 2021 07:18:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236732AbhHLLSF (ORCPT ); Thu, 12 Aug 2021 07:18:05 -0400 Received: from mail-io1-xd2f.google.com (mail-io1-xd2f.google.com [IPv6:2607:f8b0:4864:20::d2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4882C061798 for ; Thu, 12 Aug 2021 04:17:38 -0700 (PDT) Received: by mail-io1-xd2f.google.com with SMTP id d22so7793589ioy.11 for ; Thu, 12 Aug 2021 04:17:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2sQr7vmtUINEa0XKlK/vdTFId1lazwJ8I153LpJr+Lw=; b=agCS/MX3aDzpwCyfD0wZXU6uRRybvE2jMODPJXLCQmDC/GgJ2T3gJfgdjF94QO5MEK CVr2s+BSnnv/RQ35HdOkDi/l1PMGMNsreUyAPoHH9qn8kzhflwSoaUG2AAEVHkU2IhVJ 8syu8PV/DEFE0xcag22dbqORJLyB6WskMyK56oJ2Ad5BbkiVRTP1AuhucbSkYAv1K4VG jmCCtl4t054SCppeYGppFTftbKKGtnRPmTLpnVWjuYIF3AbFiDJCOVa8FBEzeDmRF6NR hgvPUa2kdy8PcU0PDqlXS2Sd8+FHcO///Fo9w5ubIbGkn1HjPWUOaGWBL/KtQ8BdmuUf emeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2sQr7vmtUINEa0XKlK/vdTFId1lazwJ8I153LpJr+Lw=; b=fIHIoFQ1qnsEtNd3JepfOja+KJVX1VBfJRC5SLuj7QosAIELAj4nm9vYoq8qmzBBst vYSAsJsQv5qht5nEzGnYUOpgsWAX0unHxKWHvIwBBhbrZl/bqBCvg9SGYFEaNEdL4jIj wY6giZcxYpGgMKpf2Wve0rwodZGnyl9pIa5Korh9quth7Ul4WiSYRHUqu9e+/UFqm+9u k3xQLX13fxoiRLXHGVKqtB3abuXqN0jXbuOJDl5TS8gv1qpKqhaNFGDugRev8VJ8gR7S h3gyokBCH8aPT6gzfY3o3bPSrTbQQWGb0sU2+B8R87n6vXUz0Xo+rV0KZJtS6GEfmw/F 9JSQ== X-Gm-Message-State: AOAM532BfZxtBc0l6+9Z9d3yPbrSnBIZyUK64bEXP+SYdoPOxSk+nzXP 7rhdZ3psOiyCf/zikvQ9lQsQdEaGSqOPpZvxxtw= X-Google-Smtp-Source: ABdhPJyiYkIIbkDaCUMEphd/WrPdFAyvJ8zYH8wPBwdwSouNDnaw67j15T7FeOsgPug+UaTRtJgL40HinFdadwswepY= X-Received: by 2002:a05:6602:48c:: with SMTP id y12mr2673303iov.14.1628767058357; Thu, 12 Aug 2021 04:17:38 -0700 (PDT) MIME-Version: 1.0 References: <20210706041820.1536502-1-chenhuacai@loongson.cn> <20210706041820.1536502-8-chenhuacai@loongson.cn> In-Reply-To: From: Huacai Chen Date: Thu, 12 Aug 2021 19:17:26 +0800 Message-ID: Subject: Re: [PATCH 07/19] LoongArch: Add process management To: Peter Zijlstra Cc: Arnd Bergmann , Huacai Chen , Andy Lutomirski , Thomas Gleixner , Andrew Morton , David Airlie , Linus Torvalds , linux-arch , Xuefeng Li , Jiaxun Yang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org Hi, Peter and Arnd, On Tue, Jul 6, 2021 at 7:09 PM Peter Zijlstra wrote: > > On Tue, Jul 06, 2021 at 12:16:37PM +0200, Arnd Bergmann wrote: > > On Tue, Jul 6, 2021 at 6:18 AM Huacai Chen wrote: > > > > > +void arch_cpu_idle(void) > > > +{ > > > + local_irq_enable(); > > > + __arch_cpu_idle(); > > > +} > > > > This looks racy: What happens if an interrupt is pending and hits before > > entering __arch_cpu_idle()? > > They fix it up in their interrupt handler by moving the IP over the > actual IDLE instruction.. > > Still the above is broken in that local_irq_enable() will have all sorts > of tracing, but RCU is disabled at this point, so it is still very much > broken. This is a sad story, the idle instruction cannot execute with irq disabled, we can only copy ugly code from MIPS. Huacai