From patchwork Fri Apr 24 03:32:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 226973 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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 70C5FC5518A for ; Fri, 24 Apr 2020 03:32:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F61D2084D for ; Fri, 24 Apr 2020 03:32:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587699135; bh=heYBxyRSj6OCmDC8ifkTZrTjLvYjcxlqxGx3/mMEEfM=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=FKZjRKpBlNMKuXTPo+fqJZFKvP972WUT9TkzBUtHr3jQad2RUFPo8yj6sFPH6rBDR fAKUmYf65NWM2CyXb3r9+zu2RHWAfiSC0Xpff7O8Tb4lI0Yk3Zdk6zePvNe6KgnAYq eT2pAbDixXHBY3f4QT+nIorgxpfZ6QcjAHsORqZU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725922AbgDXDcP (ORCPT ); Thu, 23 Apr 2020 23:32:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:41826 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725888AbgDXDcO (ORCPT ); Thu, 23 Apr 2020 23:32:14 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B04A320715; Fri, 24 Apr 2020 03:32:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587699134; bh=heYBxyRSj6OCmDC8ifkTZrTjLvYjcxlqxGx3/mMEEfM=; h=Date:From:To:Subject:In-Reply-To:From; b=ltAJ2OTIhE3L6u1YdG/qUhtRaT9KYhoxi55ErXlp9wTMEeMJXTy3Dq1yD20kkzF/Y gOV0uuInsAcG2d3RY31fzfJ+gGOyS3oQoANKOWAJIoF8abV8j/JRgEPP90JXpZmuur fw1gC5wpVQ8jWFbcwiSn+uGerYmkjKbeIzk6KtPU= Date: Thu, 23 Apr 2020 20:32:13 -0700 From: Andrew Morton To: jbaron@akamai.com, khazhy@google.com, mm-commits@vger.kernel.org, r@hev.cc, rpenyaev@suse.de, stable@vger.kernel.org, viro@zeniv.linux.org.uk Subject: + eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch added to -mm tree Message-ID: <20200424033213.WRxjDVHj1%akpm@linux-foundation.org> In-Reply-To: <20200420181310.c18b3c0aa4dc5b3e5ec1be10@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback has been added to the -mm tree. Its filename is eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Khazhismel Kumykov Subject: eventpoll: fix missing wakeup for ovflist in ep_poll_callback In the event that we add to ovflist, before 339ddb53d373 we would be woken up by ep_scan_ready_list, and did no wakeup in ep_poll_callback. With that wakeup removed, if we add to ovflist here, we may never wake up. Rather than adding back the ep_scan_ready_list wakeup - which was resulting un uncessary wakeups, trigger a wake-up in ep_poll_callback. We noticed that one of our workloads was missing wakeups starting with 339ddb53d373 and upon manual inspection, this wakeup seemed missing to me. With this patch added, we no longer see missing wakeups. I haven't yet tried to make a small reproducer, but the existing kselftests in filesystem/epoll passed for me with this patch. Link: http://lkml.kernel.org/r/20200424025057.118641-1-khazhy@google.com Fixes: 339ddb53d373 ("fs/epoll: remove unnecessary wakeups of nested epoll") Signed-off-by: Khazhismel Kumykov Cc: Alexander Viro Cc: Roman Penyaev Cc: Heiher Cc: Jason Baron Cc: Signed-off-by: Andrew Morton --- fs/eventpoll.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/eventpoll.c~eventpoll-fix-missing-wakeup-for-ovflist-in-ep_poll_callback +++ a/fs/eventpoll.c @@ -1240,7 +1240,7 @@ static int ep_poll_callback(wait_queue_e if (epi->next == EP_UNACTIVE_PTR && chain_epi_lockless(epi)) ep_pm_stay_awake_rcu(epi); - goto out_unlock; + goto out_wakeup_unlock; } /* If this file is already in the ready list we exit soon */ @@ -1249,6 +1249,7 @@ static int ep_poll_callback(wait_queue_e ep_pm_stay_awake_rcu(epi); } +out_wakeup_unlock: /* * Wake up ( if active ) both the eventpoll wait list and the ->poll() * wait list.