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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 1238EC11D34 for ; Mon, 24 Feb 2020 15:04:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E65E22082F for ; Mon, 24 Feb 2020 15:04:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728012AbgBXPDY (ORCPT ); Mon, 24 Feb 2020 10:03:24 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:50191 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727718AbgBXPDV (ORCPT ); Mon, 24 Feb 2020 10:03:21 -0500 Received: from [5.158.153.52] (helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j6FFv-0004sR-IQ; Mon, 24 Feb 2020 16:02:47 +0100 Received: from nanos.tec.linutronix.de (localhost [IPv6:::1]) by nanos.tec.linutronix.de (Postfix) with ESMTP id 46DF210408F; Mon, 24 Feb 2020 16:02:42 +0100 (CET) Message-Id: <20200224145643.365930116@linutronix.de> User-Agent: quilt/0.65 Date: Mon, 24 Feb 2020 15:01:40 +0100 From: Thomas Gleixner To: LKML Cc: David Miller , bpf@vger.kernel.org, netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Sebastian Sewior , Peter Zijlstra , Clark Williams , Steven Rostedt , Juri Lelli , Ingo Molnar , Mathieu Desnoyers , Vinicius Costa Gomes , Jakub Kicinski Subject: [patch V3 09/22] bpf: Dont iterate over possible CPUs with interrupts disabled References: <20200224140131.461979697@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org pcpu_freelist_populate() is disabling interrupts and then iterates over the possible CPUs. The reason why this disables interrupts is to silence lockdep because the invoked ___pcpu_freelist_push() takes spin locks. Neither the interrupt disabling nor the locking are required in this function because it's called during initialization and the resulting map is not yet visible to anything. Split out the actual push assignement into an inline, call it from the loop and remove the interrupt disable. Signed-off-by: Thomas Gleixner --- kernel/bpf/percpu_freelist.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/kernel/bpf/percpu_freelist.c +++ b/kernel/bpf/percpu_freelist.c @@ -25,12 +25,18 @@ void pcpu_freelist_destroy(struct pcpu_f free_percpu(s->freelist); } +static inline void pcpu_freelist_push_node(struct pcpu_freelist_head *head, + struct pcpu_freelist_node *node) +{ + node->next = head->first; + head->first = node; +} + static inline void ___pcpu_freelist_push(struct pcpu_freelist_head *head, struct pcpu_freelist_node *node) { raw_spin_lock(&head->lock); - node->next = head->first; - head->first = node; + pcpu_freelist_push_node(head, node); raw_spin_unlock(&head->lock); } @@ -56,21 +62,16 @@ void pcpu_freelist_populate(struct pcpu_ u32 nr_elems) { struct pcpu_freelist_head *head; - unsigned long flags; int i, cpu, pcpu_entries; pcpu_entries = nr_elems / num_possible_cpus() + 1; i = 0; - /* disable irq to workaround lockdep false positive - * in bpf usage pcpu_freelist_populate() will never race - * with pcpu_freelist_push() - */ - local_irq_save(flags); for_each_possible_cpu(cpu) { again: head = per_cpu_ptr(s->freelist, cpu); - ___pcpu_freelist_push(head, buf); + /* No locking required as this is not visible yet. */ + pcpu_freelist_push_node(head, buf); i++; buf += elem_size; if (i == nr_elems) @@ -78,7 +79,6 @@ void pcpu_freelist_populate(struct pcpu_ if (i % pcpu_entries) goto again; } - local_irq_restore(flags); } struct pcpu_freelist_node *__pcpu_freelist_pop(struct pcpu_freelist *s)