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 024B3C433EF for ; Tue, 19 Jul 2022 14:39:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239232AbiGSOjg (ORCPT ); Tue, 19 Jul 2022 10:39:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239349AbiGSOjB (ORCPT ); Tue, 19 Jul 2022 10:39:01 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id BE7896175 for ; Tue, 19 Jul 2022 07:34:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1658241255; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=kZg2cZmf6hGrHSxOeYKPZO01j9dYhoqI1V9JbnPWjHs=; b=CbzoO0wcYEw3848Ytu8AfLGLPOGY4ja36skJaRlztc7aLi5EE26YX+KX+EENos3pZKVSuS Z4KKnMgRYr/RSQ2S/08oghRq8yfy+FSCIdk6jYQYHtBC43rOqko0yUQr7z6+AQwirwPpLH 1oLHKlu/pvxI01QMaYM38ii604TeTxk= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-389-X8-ZaXc2PP2W0X1RxvbnlQ-1; Tue, 19 Jul 2022 10:34:07 -0400 X-MC-Unique: X8-ZaXc2PP2W0X1RxvbnlQ-1 Received: by mail-wr1-f70.google.com with SMTP id l17-20020adfc791000000b0021dc7dc268dso2315493wrg.0 for ; Tue, 19 Jul 2022 07:34:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=kZg2cZmf6hGrHSxOeYKPZO01j9dYhoqI1V9JbnPWjHs=; b=RU0Hlv03bnTpKV5g01RmYHzuPFh6w976mBLpbTwZrHYNzZvJMaf+VQbOS5Ba+iQZUu lL+S5bc02D9dldI2SfMA8979wXsfqGAPpSHMfJdhCmwRA5g4uKGG2KvioIm3b+cD2u5a Jvu2CfB4570PomvvJW0HGCq/7Pao1wjAcfaCVHIgPiq5MwYcfEWIZSsj3wXRIJKUdJgT wELsevmB1VlwaYQK0ES2YBEMbnYnOKPgSN5AjaWhJjLI/GrQ2GgCDnptzn/9gFTPJauy QPHaWNfTDbbD051D7CaURSKOTZ4P9HPaHgB/bpeepRRlROA1xfVcOmWYhArad7L83Mk8 F7Hg== X-Gm-Message-State: AJIora9XkwciHfhEM868eHqo8uorceHJcuYEhdxiGdkeDg/JJ+jvSp0f y3DmNuJP8DfSRiHbKCDPpwHo3snGRQshVhADpyDiIm92oqlf8tLFzJnQ9cIuiIQ1f1/pXTk7vwS zV5Y1kUHYq+UOv3VFirSG43bV X-Received: by 2002:a05:600c:4eca:b0:3a1:9c39:ac20 with SMTP id g10-20020a05600c4eca00b003a19c39ac20mr37375620wmq.61.1658241245564; Tue, 19 Jul 2022 07:34:05 -0700 (PDT) X-Google-Smtp-Source: AGRyM1vF2t4k1Dw5AmQrA+cG8EMbo7SySCI6IamIL1OhnNbMT7T4iiuU6S3lmVm/ECzG0GEwOTJC4w== X-Received: by 2002:a05:600c:4eca:b0:3a1:9c39:ac20 with SMTP id g10-20020a05600c4eca00b003a19c39ac20mr37375600wmq.61.1658241245397; Tue, 19 Jul 2022 07:34:05 -0700 (PDT) Received: from vschneid.remote.csb ([185.11.37.247]) by smtp.gmail.com with ESMTPSA id v10-20020a05600c428a00b003a2fc754313sm18032475wmc.10.2022.07.19.07.34.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jul 2022 07:34:04 -0700 (PDT) From: Valentin Schneider To: Phil Auld , linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH v3 1/2] cpuhp: make target_store() a nop when target == state In-Reply-To: <20220711211619.112854-2-pauld@redhat.com> References: <20220711211619.112854-1-pauld@redhat.com> <20220711211619.112854-2-pauld@redhat.com> Date: Tue, 19 Jul 2022 15:34:03 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/07/22 17:16, Phil Auld wrote: > writing the current state back in hotplug/target calls cpu_down() > which will set cpu dying even when it isn't and then nothing will > ever clear it. A stress test that reads values and writes them back > for all cpu device files in sysfs will trigger the BUG() in > select_fallback_rq once all cpus are marked as dying. > > kernel/cpu.c::target_store() > ... > if (st->state < target) > ret = cpu_up(dev->id, target); > else > ret = cpu_down(dev->id, target); > > cpu_down() -> cpu_set_state() > bool bringup = st->state < target; > ... > if (cpu_dying(cpu) != !bringup) > set_cpu_dying(cpu, !bringup); > > Fix this by letting state==target fall through in the target_store() > conditional. Also make sure st->target == target in that case. > > Signed-off-by: Phil Auld One nit below, otherwise: Reviewed-by: Valentin Schneider > --- > kernel/cpu.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index bbad5e375d3b..305694a2ca26 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -2326,8 +2326,10 @@ static ssize_t target_store(struct device *dev, struct device_attribute *attr, > > if (st->state < target) > ret = cpu_up(dev->id, target); > - else > + else if (st->state > target) > ret = cpu_down(dev->id, target); > + else if (st->target != target) Should we make this: else if (WARN(st->target != target)) > + st->target = target; > out: > unlock_device_hotplug(); > return ret ? ret : count; > -- > 2.31.1