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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 EDA20C3F68F for ; Wed, 22 Jan 2020 07:23:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5E6924125 for ; Wed, 22 Jan 2020 07:23:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579677804; bh=bbAh3rhHmfmleomVp4XItkwvBRm3+pggpqJQcYaj0pw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=hUutUUxEDY3d0c7YgLgC36vaJE5TdXFiqjMeEyA63Vwjhr3K7Ai++9fajsslvbU2c i5qJh7WLU/6aSs3m/rW8jrheDjVBcZW+I8/yu7eqd9f9x6dDwkLEJdHjfUyZ5vJmFt pldkH6u00PFSKgI2D1s9f9IIhiIDAbtxF14K3LXw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728733AbgAVHXY (ORCPT ); Wed, 22 Jan 2020 02:23:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:51794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725975AbgAVHXX (ORCPT ); Wed, 22 Jan 2020 02:23:23 -0500 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 C3E8F2253D; Wed, 22 Jan 2020 07:23:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579677802; bh=bbAh3rhHmfmleomVp4XItkwvBRm3+pggpqJQcYaj0pw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Nw68NfTqgmtfdHWRdZhjK8XTTkzkkBbqDAlHJguxpOQHBCZ9k0h8oHLITVrXovekX Jbs/lNg5w1Fhwq+h/+Sj6hWzQT0taikEShjBomAjFAmx8I0ztz8GbX86VAoaHPc8rI 8XZgNtFfpn/UKaMgEwOfoMsF67orejhKxLrwHoFI= Date: Wed, 22 Jan 2020 16:23:17 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Brendan Gregg , Alexei Starovoitov , Ingo Molnar , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Borkmann , Arnaldo Carvalho de Melo , "David S . Miller" , paulmck@kernel.org, joel@joelfernandes.org, "Naveen N . Rao" , Anil S Keshavamurthy Subject: Re: [RFT PATCH 04/13] kprobes: Make optimizer delay to 1 second Message-Id: <20200122162317.0299cf722dd618147d97e89c@kernel.org> In-Reply-To: <20200121192905.0f001c61@gandalf.local.home> References: <157918584866.29301.6941815715391411338.stgit@devnote2> <157918589199.29301.4419459150054220408.stgit@devnote2> <20200121192905.0f001c61@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, 21 Jan 2020 19:29:05 -0500 Steven Rostedt wrote: > On Thu, 16 Jan 2020 23:44:52 +0900 > Masami Hiramatsu wrote: > > > Since the 5 jiffies delay for the optimizer is too > > short to wait for other probes, make it longer, > > like 1 second. > > Hi Masami, > > Can you explain more *why* 5 jiffies is too short. Yes, I had introduced this 5 jiffies delay for multiple probe registration and unregistration like systemtap, which will use array-based interface to register/unregister. In that case, 5 jiffies will be enough for the delay to wait for other kprobe registration/unregsitration. However, since perf and ftrace register/unregister probes one-by-one with RCU synchronization interval, the optimizer will be started before finishing to register/unregister all probes. And the optimizer locks kprobe_mutex a while -- RCU-tasks synchronization. Since the kprobe_mutex is also involved in disabling kprobes, this also stops probe-event disabling. Maybe 5 jiffies is enough for adding/removing a few probe events, but not enough for dozens of probe events. Thank you, > > Thanks! > > -- Steve > > > > > Signed-off-by: Masami Hiramatsu > > --- > > kernel/kprobes.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index 0dacdcecc90f..9c6e230852ad 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -469,7 +469,8 @@ static int kprobe_optimizer_queue_update; > > > > static void kprobe_optimizer(struct work_struct *work); > > static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer); > > -#define OPTIMIZE_DELAY 5 > > +/* Wait 1 second for starting optimization */ > > +#define OPTIMIZE_DELAY HZ > > > > /* > > * Optimize (replace a breakpoint with a jump) kprobes listed on > -- Masami Hiramatsu