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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 A9A01C6787C for ; Sat, 13 Oct 2018 02:31:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 558D920868 for ; Sat, 13 Oct 2018 02:31:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dZNWozwu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 558D920868 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726340AbeJMKHD (ORCPT ); Sat, 13 Oct 2018 06:07:03 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:38821 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725970AbeJMKHD (ORCPT ); Sat, 13 Oct 2018 06:07:03 -0400 Received: by mail-pl1-f194.google.com with SMTP id q19-v6so3644056pll.5; Fri, 12 Oct 2018 19:31:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ZfrBtM5rZl984irl4Xcc+nCf/LTw6boDhHYObfCHvS4=; b=dZNWozwuTT0OzYcMzSHS67H27dkEPpkHeh2CVzkfy90W9QoHJrRE6dKFh2ToiFP5WZ i8BoJLH9kZ2gtBDOJEPEeRoIJsaUqli/3pM7lfhnPriVnNCNcXhedKAawYgkmKmKZ7Ba 5qWLialTEmtwbBnOGVQeLtSURrwGTIm/LpuHmmxfpx598J0MfLNT64YDroPCanZ4UHfX 50wDN9agG8+vi07Np7VR6BgnHE7Tp8e5cauGbt/kJIrJUBzlzLczHJt6qgKjqHoOgp7S HuUS7kaqTkxW6qnLuOBVfxUcEaX12Fn0QIYM6DpZJkIAnTjNTDeZybF/xp6V9Jn3nC4x pQ7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=ZfrBtM5rZl984irl4Xcc+nCf/LTw6boDhHYObfCHvS4=; b=bozNtBP7Ggd/Q1Fhy1BcH3O/NezSC4l28zLvWpPXqGWJ42oE7rnigZnlyULDXOpfjg 18auWl83a+d24p4LneCs/kqYSNytr+3K4O5n9TVx8bfAkmIKpXrulLQ5YLiAx7kEZj8a 5aq8gFTLZbIimByaFhBUCDYt5HCXYiTe0bUoQZR70rlZT7zusFkib6yX8Ir5sRlCWI3j 2uOdZo6o/AQLyXgWyoibJJvP/4FJ76VUTgJEtvqMua/AfIyAQOx8eFiZ43ke+MhlFEI7 Cp7SNQ0vg9RDkU0jLiHP+YYSYD/943BonRhzN77EHKWfFlffXCKFN8jAGIWZvGKr6Bv6 dGqw== X-Gm-Message-State: ABuFfojZuvC3ZPdPkNtseZJ8ic3f7z9oPUCZKab5XiR6J5bgmFxvpkdz HZBJ7wbFeH0OtUT0GUPMdvM= X-Google-Smtp-Source: ACcGV61VmXmyp5L6SWX9s4ZkyKrSdKbStqNZfuO2+qU6tg3q8f5YubMKzffxgsdAy+aSw2eKjLKeFw== X-Received: by 2002:a17:902:b611:: with SMTP id b17-v6mr8216277pls.217.1539397903806; Fri, 12 Oct 2018 19:31:43 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:180::1:4ee2]) by smtp.gmail.com with ESMTPSA id d197-v6sm3891276pga.1.2018.10.12.19.31.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Oct 2018 19:31:42 -0700 (PDT) Date: Fri, 12 Oct 2018 19:31:40 -0700 From: Alexei Starovoitov To: Daniel Colascione Cc: joelaf@google.com, linux-kernel@vger.kernel.org, timmurray@google.com, netdev@vger.kernel.org, Lorenzo Colitti , Chenbo Feng , Mathieu Desnoyers , Alexei Starovoitov , Daniel Borkmann Subject: Re: [PATCH v4] Wait for running BPF programs when updating map-in-map Message-ID: <20181013023138.m445q6itdmyxdtoc@ast-mbp.dhcp.thefacebook.com> References: <20180816040145.gqzqicab4s6kcbye@ast-mbp.dhcp.thefacebook.com> <20181012105427.243779-1-dancol@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181012105427.243779-1-dancol@google.com> User-Agent: NeoMutt/20180223 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 12, 2018 at 03:54:27AM -0700, Daniel Colascione wrote: > The map-in-map frequently serves as a mechanism for atomic > snapshotting of state that a BPF program might record. The current > implementation is dangerous to use in this way, however, since > userspace has no way of knowing when all programs that might have > retrieved the "old" value of the map may have completed. > > This change ensures that map update operations on map-in-map map types > always wait for all references to the old map to drop before returning > to userspace. > > Signed-off-by: Daniel Colascione > --- > kernel/bpf/syscall.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 8339d81cba1d..d7c16ae1e85a 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -741,6 +741,18 @@ static int map_lookup_elem(union bpf_attr *attr) > return err; > } > > +static void maybe_wait_bpf_programs(struct bpf_map *map) > +{ > + /* Wait for any running BPF programs to complete so that > + * userspace, when we return to it, knows that all programs > + * that could be running use the new map value. > + */ > + if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS || > + map->map_type == BPF_MAP_TYPE_ARRAY_OF_MAPS) { > + synchronize_rcu(); > + } extra {} were not necessary. I removed them while applying to bpf-next. Please run checkpatch.pl next time. Thanks