From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9885A195FEC for ; Thu, 28 Nov 2024 09:28:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732786089; cv=none; b=mFFQ6xs++zlyIIgqSDnXTKTx24dMp8vDeveP/L5jXeoTp7mjGIVs3HpbxD/ZbJX65mK5ZzFv2nI8HMamd40dsRj/ut1c49KACV7nBE38OHiOkPDkSblC0Y5GOmcG9RZ1o1MF58tA0Oo0bDIgiEqrPWdtOb7VKfXfp/LWzfO2f2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732786089; c=relaxed/simple; bh=aMpYn4R0EIeydkdloBQcGhRW0AGtuXc3BSIgeKf6BEk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FpMRYv9JVb4ZipKCnXKsssQgzy6zV4mCSh5GVk/A3Y1lPhGPnuluoik1fxDaSPaWaZQ4AvXaF4cXol6l7oh+vOXFBwBnf/LwjVUM3cB+tTbm1+BY+iW8+fbmIbQ4chuRKJrItj0kj8R2dcfiRzZ6VdFCxi8cfxyScXC18OAlUKM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=TSA0kfjl; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="TSA0kfjl" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=aMpYn4R0EIeydkdloBQcGhRW0AGtuXc3BSIgeKf6BEk=; b=TSA0kfjl8tAoIqBfD8kIJ31b9d OiOFePhfMUFEdq99p4NDkKC4KTFtpA1YArnlpW9Ho8XdxoUjExHZGccU/P6HHkFVgSLGg3Gk2qgA5 YjayKybnAl0ZHv5H56eMWxlQ0qvPTDuXlGJOLswAWfFzH+oUfEFdHNTa8l+HlxR80+x5CacRQx05n 5BLCmDBVZtAMySlkbprEEiF3g2NRSvoDlKsIdrrXLjgZqvvvWbZvYK8LcuPZy8P+DKwgB1m+TeufI o26/j5uUXgyjl6RlgoMxi8lp5JJNMa8vKWF5X7dnOWmLPGaGmqqPSbEtABORgodsmh/XjN7382Nid c5E5BLng==; Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tGaob-00000001ZxL-2NTs; Thu, 28 Nov 2024 09:28:01 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 93F5330026A; Thu, 28 Nov 2024 10:28:00 +0100 (CET) Date: Thu, 28 Nov 2024 10:28:00 +0100 From: Peter Zijlstra To: Waiman Long Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org, "H. Peter Anvin" Subject: Re: [PATCH] x86/nmi: Use trylock in __register_nmi_handler() when in_nmi() Message-ID: <20241128092800.GB35539@noisy.programming.kicks-ass.net> References: <20241127233455.76904-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241127233455.76904-1-longman@redhat.com> On Wed, Nov 27, 2024 at 06:34:55PM -0500, Waiman Long wrote: > The __register_nmi_handler() function can be called in NMI context from > nmi_shootdown_cpus() leading to a lockdep splat like the following. This seems fundamentally insane. Why are we okay with this?