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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 BCF5AC432C3 for ; Fri, 15 Nov 2019 20:43:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91C8020733 for ; Fri, 15 Nov 2019 20:43:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=netronome-com.20150623.gappssmtp.com header.i=@netronome-com.20150623.gappssmtp.com header.b="L4BOM+ma" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726995AbfKOUnC (ORCPT ); Fri, 15 Nov 2019 15:43:02 -0500 Received: from mail-lf1-f68.google.com ([209.85.167.68]:39588 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726549AbfKOUnC (ORCPT ); Fri, 15 Nov 2019 15:43:02 -0500 Received: by mail-lf1-f68.google.com with SMTP id j14so8973270lfk.6 for ; Fri, 15 Nov 2019 12:43:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :organization:mime-version:content-transfer-encoding; bh=t1kmXn3DyN+oFbpE0GUcOMwvt7CaLBdPQtzGMkEvuuo=; b=L4BOM+ma7vZ+5IMmlzYDyPuXeIG8inY6qKkKLmdIa6fwTU1Oox/CRwFDH6cEUwPHvn gUhmjArFefBw2iBF0sXANS3OtgQ9ldypJP+hiBYPfEslHky01GluebRRvCmT64ajDOd9 W1SQkD+Mryy7+KtbKHkBoaLJRcO/GVJZX6ez7FQKD7XRFxdq3Z/lXV7wrAku7l6OZaQQ t9qIEEnzXTQaz63YQainhYftsVm15y8xLJ0dwDHCsSN4Z9HZj6cr8Dz7xV9D7Ks+KU23 aY3lg9rfRbycQaoDe2H0h6YeiLJ03jXx/1FdYNhWl3uD39HDxc0e/B8NNRvF3UMHlI/1 x06w== 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:in-reply-to :references:organization:mime-version:content-transfer-encoding; bh=t1kmXn3DyN+oFbpE0GUcOMwvt7CaLBdPQtzGMkEvuuo=; b=dZK5ByebzcY6YyD+00bgU+QyzB+uPQSSwm0R3jantF4ja8lLyfykxM5IYS4hnx++dq 9NpEdjgDRi0OHSBj1il47qLva0ChYm+lIjbzqY//fNwbFhj0c1OhZcfuk6zsyytyHxRu lEglUNf6UiPdUIXmsjoyTMkEF/okPh1HzeFPRfsI36VCnuKzGpf302DYsXrFDXIofL5f x0SVhYkiqxNEGApHV3/QRCTtqZ/PHFDM9xOqvIeIkeCyj2noHz7IBEvwn6UIHDyxW1MD sXjejmzJLAVpWkzPHwMiuX2zdzAVuU1vDtW0Kn3O9hWJBvWLdBmACR7K0QnOTW4aIBzF U3Wg== X-Gm-Message-State: APjAAAVZ1ehK2XIiqlDxYCo1z9xwx18iUtUrrwaj23Qub21CavfZsNUS U+E9FKr5Zg2Kya08NkV4osfHNw== X-Google-Smtp-Source: APXvYqxfIcKVLtbBh2FpSLw2e7hTrC36NJile3EdMyK78ZMtjgyZxfmfvXXqKdVHw+zm2Tv0rY9Dfw== X-Received: by 2002:a19:cb4a:: with SMTP id b71mr12475061lfg.90.1573850579868; Fri, 15 Nov 2019 12:42:59 -0800 (PST) Received: from cakuba.netronome.com ([66.60.152.14]) by smtp.gmail.com with ESMTPSA id 30sm4539202ljw.29.2019.11.15.12.42.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2019 12:42:59 -0800 (PST) Date: Fri, 15 Nov 2019 12:42:49 -0800 From: Jakub Kicinski To: Andrii Nakryiko Cc: Alexei Starovoitov , Andrii Nakryiko , bpf , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team , Johannes Weiner , Rik van Riel Subject: Re: [PATCH v4 bpf-next 2/4] bpf: add mmap() support for BPF_MAP_TYPE_ARRAY Message-ID: <20191115124249.0ad3496d@cakuba.netronome.com> In-Reply-To: References: <20191115040225.2147245-1-andriin@fb.com> <20191115040225.2147245-3-andriin@fb.com> <20191115044518.sqh3y3bwtjfp5zex@ast-mbp.dhcp.thefacebook.com> <20191115050824.76gmttbxd32jnnhb@ast-mbp.dhcp.thefacebook.com> Organization: Netronome Systems, Ltd. 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, 15 Nov 2019 08:36:56 -0800, Andrii Nakryiko wrote: > Alternatively we can use spinlock. I don't think it's too ugly, tbh. See below. > > From 0da495b911adad495857f1c0fc3596f1d06a705f Mon Sep 17 00:00:00 2001 > From: Andrii Nakryiko > Date: Fri, 15 Nov 2019 08:32:43 -0800 > Subject: [PATCH bpf-next] bpf: switch freeze locking to use spin_lock and save > space > > Switch to spin_lock in favor of mutex. Due to mmap-ing itself happening not > under spinlock, there needs to be an extra "correction" step for writecnt, if > mapping fails. FWIW I was pondering that too, and thought your initial design was nicer, the transient errors sometimes become a major PITA.