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=-6.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 155B5C43461 for ; Thu, 17 Sep 2020 06:33:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A408820707 for ; Thu, 17 Sep 2020 06:33:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="RZMGGdrU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726273AbgIQGdi (ORCPT ); Thu, 17 Sep 2020 02:33:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726109AbgIQGde (ORCPT ); Thu, 17 Sep 2020 02:33:34 -0400 Received: from mail-qv1-xf44.google.com (mail-qv1-xf44.google.com [IPv6:2607:f8b0:4864:20::f44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5FFB1C061756 for ; Wed, 16 Sep 2020 23:33:34 -0700 (PDT) Received: by mail-qv1-xf44.google.com with SMTP id q10so466830qvs.1 for ; Wed, 16 Sep 2020 23:33:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=C33+1DOqnTOdhGEShIG3XwfWH0GCMYX8FFAlfTyHRQk=; b=RZMGGdrUq5VvBwNoudF+YLRuvCQOaepLpAKGZTFjM1tgqFw2xBnoKhcDdkVPEGTYt4 R2dNLvD6wlqoz0+RPcN0qHmUozglwOIL1qFO7CVY4JEAjh8dTHbUjKMSABe0j9K/PZ+7 4oFdFEVAUBLyJuz+zRKwGX67a+oMOEuB1j6P37HLxnjdKUSd/wJyUaNpN0WuWYpcEPCN s79iBtph4ObtoCWxx2N0SAy4w9bluc7xsXC67ey7DXeCH2CrH1mRfcQtIzvAnHDBDfRW 74Az4lWPq+cmouAnZIm1I4Y4t+iygx/lg7JaQsg+yOrQQixpOCXiTngrKTDy8OjzGtH4 SzZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=C33+1DOqnTOdhGEShIG3XwfWH0GCMYX8FFAlfTyHRQk=; b=P4SIcKMNQReLyEJGlNb6izJNjG2+5dVRc5wpRIzDoOMQfBhQFUr1Och8WMzN8z+K6i s2BFOb6kOmnhO4IxPMrKa6H/v0w4iqzsBwEowAG18RQSKJI3RiKTvt4/sPnpyAaGfFg7 0qZOOUpx5CP/anyov1ifjUw/kkZjrzEJZtqHWViyOhYdzfsrA5U2sYoy64zS62EREIGD DjJNPpAvWHgDNILRtWuMnNcqQi7WjfcIREARgSqFrxcJHZ+5e5Yd4dh2rVyK54BNAo/k JtZysOdb6DYKb2NFaYH2UaQQ1eAOZbYUqRlyrEtZXZf/+08xdpXR7McZYYYBZrfdkOyn XfDw== X-Gm-Message-State: AOAM532J9pwCJ75xvYwLVdGD/STtSF4HO/ZS5ZHW1w5KflsS26NTu7ve kL460Zs3GNowC3bXsTpvuVbN+uRRjqC0/oPPlk6j5W9ipB4= X-Google-Smtp-Source: ABdhPJzSj82M17alFDek6U+fYB0GBjnfm5rfbgVwaP6KwQ4CDHW0KnAQEKKIPAZAxHTp1klKnimcbdal/i8MfWvQk60= X-Received: by 2002:ad4:45b3:: with SMTP id y19mr10773997qvu.59.1600324412443; Wed, 16 Sep 2020 23:33:32 -0700 (PDT) MIME-Version: 1.0 References: <20200917020021.0860995C06B9@us180.sjc.aristanetworks.com> In-Reply-To: <20200917020021.0860995C06B9@us180.sjc.aristanetworks.com> From: Francesco Ruggeri Date: Wed, 16 Sep 2020 23:33:21 -0700 Message-ID: Subject: Re: [PATCH] net: make netdev_wait_allrefs wake-able To: open list , netdev , xiyou.wangcong@gmail.com, ap420073@gmail.com, andriin@fb.com, Eric Dumazet , jiri@mellanox.com, ast@kernel.org, Jakub Kicinski , David Miller , Francesco Ruggeri Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > static inline void dev_put(struct net_device *dev) > { > + struct task_struct *destroy_task = dev->destroy_task; > + > this_cpu_dec(*dev->pcpu_refcnt); > + if (destroy_task) > + wake_up_process(destroy_task); > } I just realized that this introduces a race, if dev_put drops the last reference, an already running netdev_wait_allrefs runs to completion and then dev_put tries to wake it up. Any suggestions on how to avoid this without resorting to locking? Thanks, Francesco