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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 B9E9BC34047 for ; Wed, 19 Feb 2020 16:54:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F27B2464E for ; Wed, 19 Feb 2020 16:54:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726582AbgBSQyT (ORCPT ); Wed, 19 Feb 2020 11:54:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:36590 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726528AbgBSQyT (ORCPT ); Wed, 19 Feb 2020 11:54:19 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 828E42465D; Wed, 19 Feb 2020 16:54:17 +0000 (UTC) Date: Wed, 19 Feb 2020 11:54:15 -0500 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , David Miller , bpf@vger.kernel.org, netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Sebastian Sewior , Peter Zijlstra , Clark Williams , Juri Lelli , Ingo Molnar Subject: Re: [RFC patch 04/19] bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run() Message-ID: <20200219115415.57ee6d3c@gandalf.local.home> In-Reply-To: <20200214161503.289763704@linutronix.de> References: <20200214133917.304937432@linutronix.de> <20200214161503.289763704@linutronix.de> X-Mailer: Claws Mail 3.17.3 (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: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, 14 Feb 2020 14:39:21 +0100 Thomas Gleixner wrote: > __bpf_trace_run() disables preemption around the BPF_PROG_RUN() invocation. > > This is redundant because __bpf_trace_run() is invoked from a trace point > via __DO_TRACE() which already disables preemption _before_ invoking any of > the functions which are attached to a trace point. > > Remove it. > > Signed-off-by: Thomas Gleixner > --- > kernel/trace/bpf_trace.c | 2 -- > 1 file changed, 2 deletions(-) > > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -1476,9 +1476,7 @@ static __always_inline > void __bpf_trace_run(struct bpf_prog *prog, u64 *args) > { Should there be a "cant_migrate()" added here? -- Steve > rcu_read_lock(); > - preempt_disable(); > (void) BPF_PROG_RUN(prog, args); > - preempt_enable(); > rcu_read_unlock(); > } >