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=-3.9 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,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 4256BC433E7 for ; Mon, 12 Oct 2020 19:28:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F07C920776 for ; Mon, 12 Oct 2020 19:28:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602530939; bh=6v2HDA9ciiuGrXPKUtzSAd2UPX53AAfbxySMLrU/uWc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=V2Nu7KS+Un/M/a2bry5MH9rDLB3GeRLH/PkK4yxGw4vEkZm41UnZO62WXIbcC+M7N LWDv71fUFG9eanSNh8k46y8kTLJTSsWk5m3wXTXQ66+AC9fsiIH8LLDuU2ExJE9+rs /znjGrXhyVvxddCfhYQQDm3taTStycBmscN9nF8E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389463AbgJLT26 (ORCPT ); Mon, 12 Oct 2020 15:28:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387797AbgJLT26 (ORCPT ); Mon, 12 Oct 2020 15:28:58 -0400 Received: from mail-lj1-x243.google.com (mail-lj1-x243.google.com [IPv6:2a00:1450:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10919C0613D0 for ; Mon, 12 Oct 2020 12:28:58 -0700 (PDT) Received: by mail-lj1-x243.google.com with SMTP id c21so17955141ljn.13 for ; Mon, 12 Oct 2020 12:28:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=PBBv8x0EA+jyMbeGbj2AD5+EOk9EuJpVDyEvfsZ1FnQ=; b=Sg/dv0+6q/T5D5BigWu87HiS3Oyz1Gx2mRS8WRM0qJR+ZvzBax9hT9Li7FBVJE0ydo qxNsvOzo9+2aL74hch0pe/IBE/A3RgBB2mlynpMG99k3j8N5fOXAJq6TsU1kqDdSiWNJ 88IXcUyrzO2MAL00aCNG8np3MdgE/b4+Tqkog= 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:cc; bh=PBBv8x0EA+jyMbeGbj2AD5+EOk9EuJpVDyEvfsZ1FnQ=; b=q4ubZXkH7ElQNGzt+Yss86iJCeXx81mRqzhCLMPjdcrsYlnqFOeSV2tTMkqX2I7sVK wPAq6rwDJuwxiIWijwahZDzeSpsoxbn3LkpBhCNVKJTmX3bddERrbzs0AxR4NQEwJgmh oVvbUa6I0qhXHKsE/nyQ3rsmLj19PON+C8e8qat/CU4LJcDQ8+5DDmrlgtLjXcD/x6Yo pzl9isPht7tNk5r9L+V7tFeVw2gWR4iDB0DUX8jO3yLf+tHUUWfV7kNwwWf9wAEIMJYx bEpaJeA8sybVNLM73psI9bvDMT+R4B3VVQuJZ/dp7vy9+yVZHkbgwITl3DPF2BfKbaXE aR/g== X-Gm-Message-State: AOAM530hK/WqLi0ByIUgb0hbyYJ8BoRhUiPEQi6kBS1ObHm5f8oQu8+2 ltWLCv9A/3c9MGpjUJCu932gC3/AAs7cDQ== X-Google-Smtp-Source: ABdhPJzKDl6ifvH/KP74BYVHgAo4DVUpM+IOwFhqhCtoThOFa30UynNFVyjHqqQ6Lvo5YqQ8XZTe6w== X-Received: by 2002:a2e:924d:: with SMTP id v13mr2528151ljg.375.1602530935583; Mon, 12 Oct 2020 12:28:55 -0700 (PDT) Received: from mail-lj1-f169.google.com (mail-lj1-f169.google.com. [209.85.208.169]) by smtp.gmail.com with ESMTPSA id m19sm1508396lfl.38.2020.10.12.12.28.54 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Oct 2020 12:28:54 -0700 (PDT) Received: by mail-lj1-f169.google.com with SMTP id f29so4130281ljo.3 for ; Mon, 12 Oct 2020 12:28:54 -0700 (PDT) X-Received: by 2002:a2e:9152:: with SMTP id q18mr10194176ljg.421.1602530934167; Mon, 12 Oct 2020 12:28:54 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Mon, 12 Oct 2020 12:28:38 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Regression: epoll edge-triggered (EPOLLET) for pipes/FIFOs To: Michael Kerrisk-manpages , Alexander Viro Cc: David Howells , Rasmus Villemoes , Greg Kroah-Hartman , Peter Zijlstra , Nicolas Dichtel , Ian Kent , Christian Brauner , keyrings@vger.kernel.org, "linux-fsdevel@vger.kernel.org" , Linux API , lkml Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, Oct 12, 2020 at 12:25 PM Linus Torvalds wrote: > > Now, the old pipe behavior was that it would wake up writers whether > they needed it or not [..] That "writers" should be "readers", of course. Although yes, that commit changed it for both readers and writers: if the pipe was readable from before, then a writer adding new data to it doesn't make it "more readable". Similarly, if a pipe was writable before, and a reader made even more room in it, the pipe didn't get "more writable". So that commit removes the pointless extra wakeup calls that don't actually make any sense (and that gave incorrect edges to the some EPOLL case that saw an edge that didn't actually exist). Linus