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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 0F684C31E5B for ; Wed, 19 Jun 2019 01:11:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D768921479 for ; Wed, 19 Jun 2019 01:11:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560906700; bh=cCLF6K6FQ3FcTT774CCrJNrNFM6jLvOhU6dCYKbghcE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=u1Q4UvBRBOnk4qJnhZbWJ94iAFKLIzpLvXXOhFITt8dfLozcpD41KUzlSy1YJFezD JmOb65xXsJwTssYs74zsuje6VJeX3WH15cnYQMoI2K4H1NU0rW4jYiPbVcK0XiskEM orDFFg8s51AOmiesKDnENWCNM26YCsyO8qYSLits= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729689AbfFSBLj (ORCPT ); Tue, 18 Jun 2019 21:11:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:44382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbfFSBLj (ORCPT ); Tue, 18 Jun 2019 21:11:39 -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 1C9692085A; Wed, 19 Jun 2019 01:11:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560906697; bh=cCLF6K6FQ3FcTT774CCrJNrNFM6jLvOhU6dCYKbghcE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qMOAk/EBl04SON3xurLy888U+L1ftFG74OMjHcN818LgQZ9+Jkb7rWz4LiWOEqLg7 YflD9UPQWYeX5Iz3tS/04IFlQM1ZWPwcpqHbSFVqxOPCd4P/j/O7mlsYdboHfe9b5F yXzcoJ0OMB8DVl67rce5O1obdZ7SvRdJtxTiexSk= Date: Wed, 19 Jun 2019 10:11:33 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Tom Zanussi , Ravi Bangoria , Namhyung Kim , Arnaldo Carvalho de Melo Subject: Re: [PATCH 10/21] tracing/probe: Split trace_event related data from trace_probe Message-Id: <20190619101133.f5aa78eac7a1cce4c24ae802@kernel.org> In-Reply-To: <20190618122322.6875b643@gandalf.local.home> References: <155931578555.28323.16360245959211149678.stgit@devnote2> <155931589667.28323.6107724588059072406.stgit@devnote2> <20190617215643.05a33541@oasis.local.home> <20190619011409.1a459906c14b8c851a5eb518@kernel.org> <20190618122322.6875b643@gandalf.local.home> X-Mailer: Sylpheed 3.5.1 (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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Jun 2019 12:23:22 -0400 Steven Rostedt wrote: > On Wed, 19 Jun 2019 01:14:09 +0900 > Masami Hiramatsu wrote: > > > On Mon, 17 Jun 2019 21:56:43 -0400 > > Steven Rostedt wrote: > > > > > > > +static nokprobe_inline struct trace_kprobe * > > > > +trace_kprobe_primary_from_call(struct trace_event_call *call) > > > > +{ > > > > + struct trace_probe *tp = trace_probe_primary_from_call(call); > > > > + > > > > + return container_of(tp, struct trace_kprobe, tp); > > > > > > > > > Hmm, is there a possibility that trace_probe_primary_from_call() may > > > not have a primary? > > > > Good question! Of course if given event_call is not a kprobe event, > > it doesn't have primary (or any) trace_probe. But that must not happen > > unless user misuses it. > > And that list never be the empty, when the last trace probe is released, > > the event_call also unregistered and released. See unregister_trace_kprobe() > > for details. If there is no siblings on the list, the event_call is also > > unregistered before unregistering kprobes, and after unregistering kprobes > > the list is unlinked. > > (Note that unregister_kprobe() will wait a quiescence period > > before return. This means all probe handlers are done before that.) > > Yeah, I thought something like that. But perhaps the > trace_probe_primary_from_call() code should add a WARN_ON() is the list > is empty. OK, I'll add that, and check in all callers. > > > > > > > > - ret = __enable_trace_kprobe(tk); > > > > - if (ret) { > > > > + enabled = false; > > > > + list_for_each_entry(pos, trace_probe_probe_list(tp), list) { > > > > + tk = container_of(pos, struct trace_kprobe, tp); > > > > + ecode = __enable_trace_kprobe(tk); > > > > + if (ecode) > > > > + ret = ecode; /* Save the last error code */ > > > > + else > > > > + enabled = true; > > > > > > So, if we have some enabled but return an error code, what should a > > > caller think of that? Wouldn't it be an inconsistent state? > > > > Oops, good catch! > > This part is related to caller (ftrace/perf) so should be more careful. > > Usually, kprobe enablement should not fail. If one of them has > > gone (like a probe on unloaded module), it can be fail but that > > should be ignored. I would like to add some additional check so that > > - If all kprobes are on the module which is unloaded, enablement > > must be failed and return error. > > - If any kprobe is enabled, and others are on non-exist modules, > > it should succeeded and return OK. > > - If any kprobe caused an error not because of unloaded module, > > all other enablement should be canceled and return error. > > > > Is that OK for you? > > > > Sounds good to me. Thank you! -- Masami Hiramatsu