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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 87EA2C35669 for ; Fri, 21 Feb 2020 22:21:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E935206D7 for ; Fri, 21 Feb 2020 22:21:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582323708; bh=U/Oe2Su9cuXS7/C3XLr+LnlhDygRGvtF3EzpD4iJeKY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=iRd5opOlm23XyP4CKBo9fv7tYMlX0iE/OtK34Rt5TZ77QcNMos9fnFHY1eCOBZAGm skR0u4ofrEEosfVtd6nM19mrTyAlVhZlQ1r6B93h66C42FeiEUFFVoDqYiUYmyRiCn OZDaxe/QxRpdbCXezoGWk02T+DJMIGeMa6yoaHU0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728405AbgBUWVd (ORCPT ); Fri, 21 Feb 2020 17:21:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:51716 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726731AbgBUWVc (ORCPT ); Fri, 21 Feb 2020 17:21:32 -0500 Received: from localhost (lfbn-ncy-1-985-231.w90-101.abo.wanadoo.fr [90.101.63.231]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A9E95206EF; Fri, 21 Feb 2020 22:21:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582323692; bh=U/Oe2Su9cuXS7/C3XLr+LnlhDygRGvtF3EzpD4iJeKY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mwDTTULy0+GJiAIQNMKNw6SrH+g+EQukVaXs8PSIYZHhbcGmJvpqFnWHqZi0/yrfU n/6ZtG9Olr90e7B1THF5lFr7PosQFm0DVYE3beSXlddM9Lm5s+vnntqCZARt3ocu+r khkX0m5CocedMaPFXA22dN3eoErFRG9lMJbiOOQc= Date: Fri, 21 Feb 2020 23:21:30 +0100 From: Frederic Weisbecker To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, dan.carpenter@oracle.com, mhiramat@kernel.org, Will Deacon , Petr Mladek , Marc Zyngier Subject: Re: [PATCH v4 02/27] hardirq/nmi: Allow nested nmi_enter() Message-ID: <20200221222129.GB28251@lenoir> References: <20200221133416.777099322@infradead.org> <20200221134215.149193474@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200221134215.149193474@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 21, 2020 at 02:34:18PM +0100, Peter Zijlstra wrote: > Since there are already a number of sites (ARM64, PowerPC) that > effectively nest nmi_enter(), lets make the primitive support this > before adding even more. > > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Petr Mladek > Acked-by: Will Deacon > Acked-by: Marc Zyngier > --- > arch/arm64/include/asm/hardirq.h | 4 ++-- > arch/arm64/kernel/sdei.c | 14 ++------------ > arch/arm64/kernel/traps.c | 8 ++------ > arch/powerpc/kernel/traps.c | 22 ++++++---------------- > include/linux/hardirq.h | 5 ++++- > include/linux/preempt.h | 4 ++-- > kernel/printk/printk_safe.c | 6 ++++-- > 7 files changed, 22 insertions(+), 41 deletions(-) > > --- a/kernel/printk/printk_safe.c > +++ b/kernel/printk/printk_safe.c > @@ -296,12 +296,14 @@ static __printf(1, 0) int vprintk_nmi(co > > void notrace printk_nmi_enter(void) > { > - this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK); > + if (!in_nmi()) > + this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK); > } > > void notrace printk_nmi_exit(void) > { > - this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK); > + if (!in_nmi()) > + this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK); > } If the outermost NMI is interrupted while between printk_nmi_enter() and preempt_count_add(), there is still a risk that we race and clear?