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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,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 5061DC282C3 for ; Fri, 25 Jan 2019 02:34:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21978218D0 for ; Fri, 25 Jan 2019 02:34:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GpsYL6s9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728839AbfAYCeI (ORCPT ); Thu, 24 Jan 2019 21:34:08 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:41281 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728606AbfAYCeH (ORCPT ); Thu, 24 Jan 2019 21:34:07 -0500 Received: by mail-pf1-f196.google.com with SMTP id b7so3989876pfi.8 for ; Thu, 24 Jan 2019 18:34:07 -0800 (PST) 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=EAKpPUuBIlc6HBeIAdYCfEFTRC60ouwmnYL+hcnNqyU=; b=GpsYL6s9x9YSaLEkIbI+f6wP4Vtf7cUZZcDtA7jSMautVw9OVvrL7r1Opz9JR40JN8 Je9yic8r+Ohs2I7iU/wzt5I6kbgsrWhJ6uw+hXBRImTdrgXaMaq4skCIDRvMf0tVaR2X 6EryicF3gdxNvwmXs0RLxcQVvQhsYJdJV0wPC8KLi/ZAvI0IWww0FsScNcSSVYbWXk7J HlCu+LXvrm7vdoVZ/l2qQkP8xefC8QEG508uEBzFnEGG76fDdylVzexAzczGg6NFdiZU eAKEKKBOhW9Qya8fqK9aqcftz6L3pj2aE3xIlO+WWZvcgrbxF+0C4zSQC3PmI7RtXh8s kyOQ== 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=EAKpPUuBIlc6HBeIAdYCfEFTRC60ouwmnYL+hcnNqyU=; b=drq+KmmchrkjnoZOu0A3XAUYo/LjtKZ/eeIIlpRgN40DyPqIJ2q0c25wBVlCH36bFn gFSm04hqI9LRq4YZzJ5JFfiFRJt6jf+hR9KS56OXkCQAhO7UpD8G+nZ0pNmHhmlRgiWX 1ybYLtyDNR7xzSwyqNqGt6P7DakXtS0KuPZ3I6grF4mL3URmU2CTyiMJAim208+hGx6D aeXEznUVhlKDkOFQ+CXSml3m1nK6XfDSFJsZzPb0AV68phE311nu3uqmk4qa+xiWA0lI Rb6zE3Yedn6rCTMm/XhkkQlrYhipdHmQRiU+CGzNO7xnKPNUkkIuVQR2QCS8QpNvqOZR 6S3g== X-Gm-Message-State: AJcUukfgISLDw/Uy/saDEUIxWXH53bcO7p4PkTDNSCd8UL3T0IZQSDW1 t0pQN+aFBmwbC8n0uzOLO6w= X-Google-Smtp-Source: ALg8bN6ghU2wERRuPChmt/KP8ucmMe6ni4puQ3GGHIcbIRrj/Kl3OMpcqUgicSgZRfzXjZSutKesIg== X-Received: by 2002:a62:36c1:: with SMTP id d184mr9155567pfa.242.1548383646482; Thu, 24 Jan 2019 18:34:06 -0800 (PST) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:200::7:5429]) by smtp.gmail.com with ESMTPSA id v13sm27888000pff.20.2019.01.24.18.34.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 24 Jan 2019 18:34:05 -0800 (PST) Date: Thu, 24 Jan 2019 18:34:03 -0800 From: Alexei Starovoitov To: Eric Dumazet Cc: Peter Zijlstra , Alexei Starovoitov , davem@davemloft.net, daniel@iogearbox.net, jakub.kicinski@netronome.com, netdev@vger.kernel.org, kernel-team@fb.com, mingo@redhat.com, will.deacon@arm.com, Paul McKenney , jannh@google.com Subject: Re: [PATCH v4 bpf-next 1/9] bpf: introduce bpf_spin_lock Message-ID: <20190125023402.34a5k62furpdismi@ast-mbp.dhcp.thefacebook.com> References: <20190124041403.2100609-1-ast@kernel.org> <20190124041403.2100609-2-ast@kernel.org> <20190124180109.GA27771@hirez.programming.kicks-ass.net> <20190124235857.xyb5xx2ufr6x5mbt@ast-mbp.dhcp.thefacebook.com> <395a3741-70c9-c345-08a4-77bc3bd3cae2@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <395a3741-70c9-c345-08a4-77bc3bd3cae2@gmail.com> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jan 24, 2019 at 06:29:55PM -0800, Eric Dumazet wrote: > > > On 01/24/2019 03:58 PM, Alexei Starovoitov wrote: > > On Thu, Jan 24, 2019 at 07:01:09PM +0100, Peter Zijlstra wrote: > > >> and from NMI ... > > > > progs are not preemptable and map syscall accessors have bpf_prog_active counters. > > So nmi/kprobe progs will not be running when syscall is running. > > Hence dead lock is not possible and irq_save is not needed. > > > Speaking of NMI, how pcpu_freelist_push() and pop() can actually work ? > > It seems bpf_get_stackid() can be called from NMI, and lockdep seems to complain loudly it's a known false positive. https://lkml.org/lkml/2018/7/25/756 and the same answer as before: we're not going to penalize performance to shut up false positive.