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 76A6021C160; Thu, 19 Jun 2025 09:45:19 +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=1750326323; cv=none; b=THYojK0+bEQQqXLK1hnPRhibR/uMlUyGqR9aStqyCEjyMI5OlbqEmNHfe/uQDtOWiA3nuRtkMyhE30ZIdmbVCmgdMH4QXW8DJapQKd74+irie9FHCCGTxL0UQnbrRxBmaR0B1uJVLdn5iTqXwqG8AAcbdXD8koJvJoJcPAQOF9Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750326323; c=relaxed/simple; bh=NnIlT7i/zvs7VO4G/USht2MjNi1sZsoz+k3lOcRMCII=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=leLAvhOdpZcNwoxZI5H/ahpFOIGQ+14rmLcoUDtz/4SII504C8WaSs04WqGxzJFdpO3VLjsLKj3dD+EdexLK5pV1Us+RvlPQsiRF8e1UtUbY55D8APFqxLPqe4ImIKLVty4/yx+4W0tU0yr/dtyVvg4y4BH9A9/dR0txKvQjKbo= 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=O43+g/bn; 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="O43+g/bn" 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=t9vGqsGMLtKz8r6e0ZtTpdqqrhT7A+2/Hsvv7xIOiPM=; b=O43+g/bntkOwapSUleSx7FqaDb TwVMBDEOoTTe8LMlVDt56bHKf0zyqymWJyTzw4tBmOF/apL/H2/2NkCtNMnNgL6lRWIObVOwuYeIH S+Q/baaeBJLpFBNh6UQXXR/MjxYSWMibgiWuRr+QrPdZquvhcawW+57zp3DOqWuQMdraPpPPjRgfI qn7kEd+kcxim8OG9q/zChioZGpIutJhiVTwwusdQQloknAOvWIqV9UttOYsdLTk+JBsPjxJdMKgeT oWuvGu8ydBOGCwQCX8esLY+0Llm2DezO3eF8hkC6fbzVaEhZAYHlXN+JkcmU/RCYORqrixaYAnIhv Ihn6JDBA==; Received: from 2001-1c00-8d82-d000-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d82:d000:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1uSBpT-00000004OfE-1W5t; Thu, 19 Jun 2025 09:45:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id A8DA130890E; Thu, 19 Jun 2025 11:45:05 +0200 (CEST) Date: Thu, 19 Jun 2025 11:45:05 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, x86@kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Josh Poimboeuf , Ingo Molnar , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , Linus Torvalds , Andrew Morton Subject: Re: [PATCH v10 07/14] unwind_user/deferred: Make unwind deferral requests NMI-safe Message-ID: <20250619094505.GC1613376@noisy.programming.kicks-ass.net> References: <20250611005421.144238328@goodmis.org> <20250611010428.938845449@goodmis.org> <20250619085717.GB1613376@noisy.programming.kicks-ass.net> <20250619093226.GH1613200@noisy.programming.kicks-ass.net> <80DBA3D8-5B52-43DB-8234-EAC51D0FC0E1@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-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: <80DBA3D8-5B52-43DB-8234-EAC51D0FC0E1@goodmis.org> On Thu, Jun 19, 2025 at 05:42:31AM -0400, Steven Rostedt wrote: > > > On June 19, 2025 5:32:26 AM EDT, Peter Zijlstra wrote: > >On Thu, Jun 19, 2025 at 05:07:10AM -0400, Steven Rostedt wrote: > > > >> Does #DB make in_nmi() true? If that's the case then we do need to handle that. > > > >Yes: #DF, #MC, #BP (int3), #DB and NMI all have in_nmi() true. > > > >Ignoring #DF because that's mostly game over, you can get them all > >nested for up to 4 (you're well aware of the normal NMI recursion > >crap). > > We probably can implement this with stacked counters. I would seriously consider dropping support for anything that can't do cmpxchg at the width you need.