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 D9FCBC433EF for ; Thu, 26 May 2022 16:06:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348116AbiEZQGa (ORCPT ); Thu, 26 May 2022 12:06:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348096AbiEZQGX (ORCPT ); Thu, 26 May 2022 12:06:23 -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 51584E08F for ; Thu, 26 May 2022 09:06:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1653581181; 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=/Y46BWpHrd9tkntXCOk51y3fuj4rMYPJnHD26/b0FwE=; b=i9EAyOChnG92hjAu1CAYm8W/7je8LWgGv7qpzlNSr2FX20YaDrEz/mDpPmPwqVooHTPNxl jiwfQ1579gUs+UQmwsI5o7ByzX/c/7I9St+ax46vKz7EqMO82MTUWiwN7fgDr68/QGBfnm Y1SkWKPB/cR8Idh0VeJt6oxWuTGrY6g= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-669-M_BZ9zLKNcWY5QZK7ylQbg-1; Thu, 26 May 2022 12:06:16 -0400 X-MC-Unique: M_BZ9zLKNcWY5QZK7ylQbg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 92956100BAB8; Thu, 26 May 2022 16:06:16 +0000 (UTC) Received: from pauld.bos.com (dhcp-17-51.bos.redhat.com [10.18.17.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 709B4400F3E8; Thu, 26 May 2022 16:06:16 +0000 (UTC) From: Phil Auld To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Peter Zijlstra , Valentin Schneider Subject: [PATCH v2 1/2] cpuhp: make target_store() a nop when target == state Date: Thu, 26 May 2022 12:06:14 -0400 Message-Id: <20220526160615.7976-2-pauld@redhat.com> In-Reply-To: <20220526160615.7976-1-pauld@redhat.com> References: <20220526160615.7976-1-pauld@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Phil Auld --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index d0a9aa0b42e8..cdb6ac10ad94 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2315,7 +2315,7 @@ 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); out: unlock_device_hotplug(); -- 2.18.0