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=-5.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 89321C10DCE for ; Fri, 6 Mar 2020 10:44:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 589C62072D for ; Fri, 6 Mar 2020 10:44:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="L8bfEK9C" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726171AbgCFKoa (ORCPT ); Fri, 6 Mar 2020 05:44:30 -0500 Received: from merlin.infradead.org ([205.233.59.134]:43358 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbgCFKoa (ORCPT ); Fri, 6 Mar 2020 05:44:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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=GIbo4YZ93wGuhbTOVPQyLk7lgLSRN+bj2GNsqZE+sDA=; b=L8bfEK9CyNcdY+WYewTkCDB4bB LKb+5qNXgAZexm3AVkxQjcbMdtXd+yFmfb+ui1sWE7rgiqvMokmdGWc1Cy1hetPrEd0tRI/ZCEMm1 T6/3R5AS0E8ZXWFxU1q+WHbIVIPLzJyCvp9k3mu0KYN0JKrcH9FlDNR9ebpmaFrKFy7y5Gy+qcYoh VlE0ih/8Es10TWs+GQt/ocNVmdVpkdiOw2OUXAUT7oAywwYwQayxisVIWZXvPwd1YCBN4yVbqJeyv LVHuD6fK3kntxAlk3OzOUIkRRoUDqqHY4j9F94xnln/VcDDjVoZ4qagekd+hbNw2qIgoZsypiLKZw k1CslHqA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jAASA-000438-VY; Fri, 06 Mar 2020 10:43:39 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id B134C980DE9; Fri, 6 Mar 2020 11:43:35 +0100 (CET) Date: Fri, 6 Mar 2020 11:43:35 +0100 From: Peter Zijlstra To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org Cc: mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org Subject: Re: [PATCH v4 16/27] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Message-ID: <20200306104335.GF3348@worktop.programming.kicks-ass.net> References: <20200221133416.777099322@infradead.org> <20200221134216.051596115@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200221134216.051596115@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 21, 2020 at 02:34:32PM +0100, Peter Zijlstra wrote: > Effectively revert commit 865e63b04e9b2 ("tracing: Add back in > rcu_irq_enter/exit_irqson() for rcuidle tracepoints") now that we've > taught perf how to deal with not having an RCU context provided. > > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Steven Rostedt (VMware) > --- > include/linux/tracepoint.h | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-) > > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -179,10 +179,8 @@ static inline struct tracepoint *tracepo > * For rcuidle callers, use srcu since sched-rcu \ > * doesn't work from the idle path. \ > */ \ > - if (rcuidle) { \ > + if (rcuidle) \ > __idx = srcu_read_lock_notrace(&tracepoint_srcu);\ > - rcu_irq_enter_irqsave(); \ > - } \ > \ > it_func_ptr = rcu_dereference_raw((tp)->funcs); \ > \ > @@ -194,10 +192,8 @@ static inline struct tracepoint *tracepo > } while ((++it_func_ptr)->func); \ > } \ > \ > - if (rcuidle) { \ > - rcu_irq_exit_irqsave(); \ > + if (rcuidle) \ > srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\ > - } \ > \ > preempt_enable_notrace(); \ > } while (0) So what happens when BPF registers for these tracepoints? BPF very much wants RCU on AFAIU.