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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A8AA0C34026 for ; Tue, 18 Feb 2020 19:50:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E23224654 for ; Tue, 18 Feb 2020 19:50:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="ieJujH8x" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726605AbgBRTul (ORCPT ); Tue, 18 Feb 2020 14:50:41 -0500 Received: from mail.skyhub.de ([5.9.137.197]:52642 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726283AbgBRTuk (ORCPT ); Tue, 18 Feb 2020 14:50:40 -0500 Received: from zn.tnic (p200300EC2F0C1F00DCB96C3517B36067.dip0.t-ipconnect.de [IPv6:2003:ec:2f0c:1f00:dcb9:6c35:17b3:6067]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 097011EC0CE8; Tue, 18 Feb 2020 20:50:39 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1582055439; 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:in-reply-to:in-reply-to: references:references; bh=Sd0idf+pvuS0yKFB+N6Kg8uZlTUf9H7N7/1BmNzZISM=; b=ieJujH8xM2RvduR1wQlc6ugEoNbuyqQ6vOPFLxmtAAlCox3aSXr5dHPE+EOwjdrUk4epH7 +moLXXcNcnCXodI/UhSwhyD38Op7FBaJhJEr4h3+pUe+BLNyM9ZPs/jPC1KRQqOd0g/R5m NuUZZvOeAukrBw/w6IqVlR/r0AhWpnw= Date: Tue, 18 Feb 2020 20:50:35 +0100 From: Borislav Petkov To: Steven Rostedt Cc: Peter Zijlstra , Andy Lutomirski , Tony Luck , x86-ml , lkml Subject: Re: [RFC] #MC mess Message-ID: <20200218195035.GN14449@zn.tnic> References: <20200218173150.GK14449@zn.tnic> <20200218131158.693eeefc@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200218131158.693eeefc@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 18, 2020 at 01:11:58PM -0500, Steven Rostedt wrote: > What's the issue with tracing? Does this affect the tracing done by the > edac_mc_handle_error code? > > It has a trace event in it, that the rasdaemon uses. Nah, that code is called from process context. The problem with tracing the #MC handler is the same as tracing the NMI handler. And the NMI handler does all kinds of dancing wrt breakpoints and nested NMIs and the #MC handler doesn't do any of that. Not sure if it should at all, btw. > I believe static_key_disable() sleeps, and does all kinds of crazing > things (like update the code). True story, thanks for that hint! static_key_disable() |-> cpus_read_lock() |-> percpu_down_read(&cpu_hotplug_lock) |->might_sleep() Yuck. Which means, the #MC handler must switch to __rdmsr()/__wrmsr() now. I wish I could travel back in time and NAK the hell of that MSR tracepoint crap. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette