From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757457AbcBSDM0 (ORCPT ); Thu, 18 Feb 2016 22:12:26 -0500 Received: from mail-pf0-f169.google.com ([209.85.192.169]:36726 "EHLO mail-pf0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757437AbcBSDMX (ORCPT ); Thu, 18 Feb 2016 22:12:23 -0500 Date: Thu, 18 Feb 2016 19:12:20 -0800 From: Alexei Starovoitov To: Sasha Levin Cc: ast@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net Subject: Re: [PATCH] bpf: grab rcu read lock for bpf_percpu_hash_update Message-ID: <20160219031219.GA86962@ast-mbp.thefacebook.com> References: <1455850582-9490-1-git-send-email-sasha.levin@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1455850582-9490-1-git-send-email-sasha.levin@oracle.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 18, 2016 at 09:56:22PM -0500, Sasha Levin wrote: > bpf_percpu_hash_update() expects rcu lock to be held and warns if it's not, > which pointed out a missing rcu read lock. > > Fixes: 15a07b338 ("bpf: add lookup/update support for per-cpu hash and array maps") > Signed-off-by: Sasha Levin > --- > kernel/bpf/syscall.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index c95a753..94324b8 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -348,7 +348,9 @@ static int map_update_elem(union bpf_attr *attr) > goto free_value; > > if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH) { > + rcu_read_lock(); > err = bpf_percpu_hash_update(map, key, value, attr->flags); > + rcu_read_unlock(); good catch. thanks, but could you add rcu_read_lock/unlock inside bpf_percpu_hash_update() instead... to match what bpf_percpu_hash_copy/bpf_percpu_array_update/bpf_percpu_array_copy are doing. Otherwise it's inconsistent.