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=-4.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS 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 91B61C433E2 for ; Thu, 3 Sep 2020 02:02:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 671AA20786 for ; Thu, 3 Sep 2020 02:02:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599098553; bh=oXS2G4ZGoJ1ZSfjgka22/QmGCif9MbzQQtgewSUYIgc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=iEXAhETX0xGv0jUmcULLxa1jJ15XaHKzDFfdm676/bSAGhvRiGwPDsGosSJwltL+H g896rxTCo2bBKfGx+xiVl27HmVqr8TXFU8EsnlP6aO+IEZ3c3P+Nhzv2X2EhVw0jgw FjKEaVT/M9w5CD1G1yUZLsH8G+hBp1+8BKtDTgNw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726528AbgICCCd (ORCPT ); Wed, 2 Sep 2020 22:02:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:51484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726177AbgICCCc (ORCPT ); Wed, 2 Sep 2020 22:02:32 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 55BC82071B; Thu, 3 Sep 2020 02:02:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599098552; bh=oXS2G4ZGoJ1ZSfjgka22/QmGCif9MbzQQtgewSUYIgc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iGBysdCDoQ7S5l2sM4OOTwhGD85kpcOGwAZRZPInk0byviyBFEHh+BAjY6AFu/XGq dg9YYWydzm5vxEBic16jogzrdIJVi5Hs7pgfLpEO1bfLab+UV5mw6PaXlzxLoyYMP1 S+ItB222EMS6Adt+KWv/seS7slNhVvdlJCkuaqNI= Date: Thu, 3 Sep 2020 11:02:26 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: peterz@infradead.org, Ingo Molnar , linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com, x86@kernel.org, davem@davemloft.net, rostedt@goodmis.org, naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, linux-arch@vger.kernel.org, cameron@moodycamel.com, oleg@redhat.com, will@kernel.org, paulmck@kernel.org, systemtap@sourceware.org Subject: Re: [PATCH v5 00/21] kprobes: Unify kretprobe trampoline handlers and make kretprobe lockless Message-Id: <20200903110226.8963179e6a7c978e2d56c595@kernel.org> In-Reply-To: <20200903103954.68f0c97da57b3679169ce3a7@kernel.org> References: <159870598914.1229682.15230803449082078353.stgit@devnote2> <20200901190808.GK29142@worktop.programming.kicks-ass.net> <20200902093739.8bd13603380951eaddbcd8a5@kernel.org> <20200902070226.GG2674@hirez.programming.kicks-ass.net> <20200902171755.b126672093a3c5d1b3a62a4f@kernel.org> <20200902093613.GY1362448@hirez.programming.kicks-ass.net> <20200902221926.f5cae5b4ad00b8d8f9ad99c7@kernel.org> <20200902134252.GH1362448@hirez.programming.kicks-ass.net> <20200903103954.68f0c97da57b3679169ce3a7@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, 3 Sep 2020 10:39:54 +0900 Masami Hiramatsu wrote: > OK, I've confirmed that the lockdep warns on kretprobe from INT3 > with your fix. Of course make it lockless then warning is gone. > But even without the lockless patch, this warning can be false-positive > because we prohibit nested kprobe call, right? > > If the kprobe user handler uses a spinlock, the spinlock is used > only in that handler (and in the context between kprobe_busy_begin/end), > it will be safe since the spinlock is not nested. > But if the spinlock is shared with other context, it will be dangerous > because it can be interrupted by NMI (including INT3). This also applied > to the function which is called from kprobe user handlers, thus user > has to take care of it. Sorry, for noticing this point, I Cc'd to systemtap. Is systemtap taking care of spinlock too? Thank you, -- Masami Hiramatsu