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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 661A2C10F25 for ; Mon, 9 Mar 2020 19:48:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 44A8220828 for ; Mon, 9 Mar 2020 19:48:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583783322; bh=Qn10r7wDKeypNpswGyjvqlxGn6R2+JzdLyxqbNYaR5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=gPIXFr8UMbG0TJpsGQyaH3svMw7O4WVsdILb6etDxDDgaHGvyltZxRlFdidFdl1IN RSAy9lSuL78Jt8+KWE5q0//GQ7qlzaWRgURijfp7G6/Ts8nXRUoEUXDjuGTsktmfyt QaRuLuzUYnyQ38deh9+cZtJ8oHHgjTx8Vtg4b0mw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726704AbgCITsS (ORCPT ); Mon, 9 Mar 2020 15:48:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:38212 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbgCITsQ (ORCPT ); Mon, 9 Mar 2020 15:48:16 -0400 Received: from localhost.localdomain (c-98-220-238-81.hsd1.il.comcast.net [98.220.238.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E5DE524656; Mon, 9 Mar 2020 19:48:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583783295; bh=Qn10r7wDKeypNpswGyjvqlxGn6R2+JzdLyxqbNYaR5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=ej7ZwgcZQjIGEm4uJBDf7OGbLnonIrkQj41AShxp7CMw0Vz4lm7eggXB4sn/ibb9r A2qR5kejQs/yUCO3GsXD3sbsR12zuGA5FJIYqwXp2xrsEC9Yqp+xz++/nnEsbIGTxZ 9bbeRBTi+rdHjPcGF9AHbNf99VyNKYHy0A73Zcbw= From: zanussi@kernel.org To: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Sebastian Andrzej Siewior , Daniel Wagner , Tom Zanussi Cc: stable-rt@vger.kernel.org Subject: [PATCH RT 1/8] userfaultfd: Use a seqlock instead of seqcount Date: Mon, 9 Mar 2020 14:47:46 -0500 Message-Id: X-Mailer: git-send-email 2.14.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sebastian Andrzej Siewior v4.14.172-rt78-rc1 stable review patch. If anyone has any objections, please let me know. ----------- [ Upstream commit dc952a564d02997330654be9628bbe97ba2a05d3 ] On RT write_seqcount_begin() disables preemption which leads to warning in add_wait_queue() while the spinlock_t is acquired. The waitqueue can't be converted to swait_queue because userfaultfd_wake_function() is used as a custom wake function. Use seqlock instead seqcount to avoid the preempt_disable() section during add_wait_queue(). Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Tom Zanussi --- fs/userfaultfd.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index e2b2196fd9428..71886a8e8f71b 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -51,7 +51,7 @@ struct userfaultfd_ctx { /* waitqueue head for events */ wait_queue_head_t event_wqh; /* a refile sequence protected by fault_pending_wqh lock */ - struct seqcount refile_seq; + seqlock_t refile_seq; /* pseudo fd refcounting */ atomic_t refcount; /* userfaultfd syscall flags */ @@ -1047,7 +1047,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, * waitqueue could become empty if this is the * only userfault. */ - write_seqcount_begin(&ctx->refile_seq); + write_seqlock(&ctx->refile_seq); /* * The fault_pending_wqh.lock prevents the uwq @@ -1073,7 +1073,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, list_del(&uwq->wq.entry); __add_wait_queue(&ctx->fault_wqh, &uwq->wq); - write_seqcount_end(&ctx->refile_seq); + write_sequnlock(&ctx->refile_seq); /* careful to always initialize msg if ret == 0 */ *msg = uwq->msg; @@ -1246,11 +1246,11 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, * sure we've userfaults to wake. */ do { - seq = read_seqcount_begin(&ctx->refile_seq); + seq = read_seqbegin(&ctx->refile_seq); need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || waitqueue_active(&ctx->fault_wqh); cond_resched(); - } while (read_seqcount_retry(&ctx->refile_seq, seq)); + } while (read_seqretry(&ctx->refile_seq, seq)); if (need_wakeup) __wake_userfault(ctx, range); } @@ -1915,7 +1915,7 @@ static void init_once_userfaultfd_ctx(void *mem) init_waitqueue_head(&ctx->fault_wqh); init_waitqueue_head(&ctx->event_wqh); init_waitqueue_head(&ctx->fd_wqh); - seqcount_init(&ctx->refile_seq); + seqlock_init(&ctx->refile_seq); } /** -- 2.14.1