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=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 AFAFCC4338F for ; Fri, 20 Aug 2021 03:27:51 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 759C8610D2 for ; Fri, 20 Aug 2021 03:27:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 759C8610D2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:Cc:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nUyggqCuW8Phl9cd2+G6fBWY+ArJVf1/36YQF4fvv4o=; b=HYtc2A7pHb3LzQ kINfcTukGA/aqPg7K8POfyHgQh5ecICi0TY5We1ytoneeil/EUfm3PRiQz0KXzt/IPzLT00IQgNV6 iy7+Q0W3rSpIPJXXInxHM3Dw+AtjdrpnoZnqdDNsBBy+m3DoEXPEupSsah/aTNLmyr1n1TkmM0lKy tcVQxvN20ubv8ju7gldxkD/u8TmsxsOxrF5VmQk7V4/x+NLF6taOebJulEmXkif+IInTqeqbQsNNt NztuyDAiEG56bbd6w+zyAuC34NO2Y5OCykVmvenrNMHaj7l+yYdpv26l0Zk+HhmM3fP5RDgbYEjd7 D+RbbzlPvJevN7whqFmA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mGvAY-009zda-85; Fri, 20 Aug 2021 03:26:10 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mGvAU-009zcq-TX for linux-arm-kernel@lists.infradead.org; Fri, 20 Aug 2021 03:26:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629429964; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oWdTs6izqiA/pimZyzqfzwAT5R8dcZcICeLEyrt5S/U=; b=iHU6DpzrUwOXz1a53EACmmf59avdBqIQoJg4M1/HFZzovs2eGqOckzhahDnN1TP6lyEZnS +Ilw9485gIiEJCSKeqIeL0OXp9UeGDZYzCg1ZV3UGykVWHFrR+BAxaIk6o5hUIHpzAdJaY LFiMSWQoc1oxAX3w2KyL50n/adYN2gk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-547-hqiP0e4XOxq-BwqdJck-_g-1; Thu, 19 Aug 2021 23:23:53 -0400 X-MC-Unique: hqiP0e4XOxq-BwqdJck-_g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AD375C73A4; Fri, 20 Aug 2021 03:23:44 +0000 (UTC) Received: from ovpn-113-78.phx2.redhat.com (ovpn-113-78.phx2.redhat.com [10.3.113.78]) by smtp.corp.redhat.com (Postfix) with ESMTP id 19C13189BB; Fri, 20 Aug 2021 03:23:37 +0000 (UTC) Message-ID: <20b9051fe47b7068ed3496bd7f5d417b1af69e3a.camel@redhat.com> Subject: Re: [PATCH] rcutorture: Avoid problematic critical section nesting on RT From: Scott Wood To: Sebastian Andrzej Siewior , Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org, linux-rt-users@vger.kernel.org, Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Steven Rostedt , Daniel Bristot de Oliveira , "Paul E. McKenney" , Frederic Weisbecker , Josh Triplett , Mathieu Desnoyers , Davidlohr Bueso , Lai Jiangshan , Joel Fernandes , Anshuman Khandual , Vincenzo Frascino , Steven Price , Ard Biesheuvel , Boqun Feng , Mike Galbraith Date: Thu, 19 Aug 2021 22:23:37 -0500 In-Reply-To: <20210817144018.nqssoq475vitrqlv@linutronix.de> References: <20210811201354.1976839-1-valentin.schneider@arm.com> <20210811201354.1976839-2-valentin.schneider@arm.com> <20210817121345.5iyj5epemczn3a52@linutronix.de> <20210817131741.evduh4fw7vyv2dzt@linutronix.de> <20210817144018.nqssoq475vitrqlv@linutronix.de> Organization: Red Hat User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210819_202607_181967_3FF5F63E X-CRM114-Status: GOOD ( 12.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 2021-08-17 at 16:40 +0200, Sebastian Andrzej Siewior wrote: > [bigeasy: remove 'preempt_disable(); local_bh_disable(); preempt_enable(); > local_bh_enable();' from the examples because this works on RT now. ] Does it actually work? If preemption is disabled during local_bh_disable, softirq_ctrl.lock won't be taken. If you then get preempted between the preempt_enable() and the local_bh_enable(), and another task tries to do local_bh_disable(), won't it successfully get softirq_ctrl.lock, add to softirq_ctrl.cnt, and proceed right into the critical section? Or am I missing something? -Scott _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel