From nobody Wed Nov 5 05:17:48 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1533311472789626.562389006165; Fri, 3 Aug 2018 08:51:12 -0700 (PDT) Received: from localhost ([::1]:51996 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1flcMB-0000AQ-0r for importer@patchew.org; Fri, 03 Aug 2018 11:51:11 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39650) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1flcLH-0008FR-3v for qemu-devel@nongnu.org; Fri, 03 Aug 2018 11:50:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1flcLG-0005zq-4p for qemu-devel@nongnu.org; Fri, 03 Aug 2018 11:50:15 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44134 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1flcLB-0005pb-OX; Fri, 03 Aug 2018 11:50:09 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B6C117788E; Fri, 3 Aug 2018 15:50:08 +0000 (UTC) Received: from lemon.usersys.redhat.com (ovpn-12-124.pek2.redhat.com [10.72.12.124]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1310A2142F20; Fri, 3 Aug 2018 15:50:04 +0000 (UTC) From: Fam Zheng To: qemu-devel@nongnu.org Date: Fri, 3 Aug 2018 23:49:55 +0800 Message-Id: <20180803154955.25251-1-famz@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 03 Aug 2018 15:50:08 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Fri, 03 Aug 2018 15:50:08 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'famz@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [RFC PATCH] async: Fix aio_notify_accept X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, Fam Zheng , qemu-block@nongnu.org, Stefan Hajnoczi Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RDMRC_1 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From main loop, bdrv_set_aio_context() can call IOThread's aio_poll(). That breaks aio_notify() because the ctx->notifier event can get cleared too early by this which causes IOThread hanging. See https://bugzilla.redhat.com/show_bug.cgi?id=3D1562750 for details. Signed-off-by: Fam Zheng --- util/async.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/util/async.c b/util/async.c index 05979f8014..c6e8aebc3a 100644 --- a/util/async.c +++ b/util/async.c @@ -355,7 +355,11 @@ void aio_notify(AioContext *ctx) =20 void aio_notify_accept(AioContext *ctx) { - if (atomic_xchg(&ctx->notified, false)) { + /* If ctx->notify_me >=3D 2, another aio_poll() is waiting which may n= eed the + * ctx->notifier event to wake up, so don't already clear it just beca= use "we" are + * done iterating. */ + if (atomic_read(&ctx->notify_me) < 2 + && atomic_xchg(&ctx->notified, false)) { event_notifier_test_and_clear(&ctx->notifier); } } --=20 2.17.1