From patchwork Mon Jan 25 10:08:18 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 8106021 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 0C595BEEE5 for ; Mon, 25 Jan 2016 10:08:34 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 79DA020279 for ; Mon, 25 Jan 2016 10:08:33 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C91292020F for ; Mon, 25 Jan 2016 10:08:32 +0000 (UTC) Received: from localhost ([::1]:36899 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aNe4W-0000i0-0D for patchwork-qemu-devel@patchwork.kernel.org; Mon, 25 Jan 2016 05:08:32 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58692) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aNe4P-0000hs-EF for qemu-devel@nongnu.org; Mon, 25 Jan 2016 05:08:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aNe4M-0006cc-7d for qemu-devel@nongnu.org; Mon, 25 Jan 2016 05:08:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41460) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aNe4M-0006cU-2L for qemu-devel@nongnu.org; Mon, 25 Jan 2016 05:08:22 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 01257106F for ; Mon, 25 Jan 2016 10:08:20 +0000 (UTC) Received: from dgilbert-t530.redhat.com (ovpn-116-97.ams2.redhat.com [10.36.116.97]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u0PA8JMD014840; Mon, 25 Jan 2016 05:08:20 -0500 From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, pbonzini@redhat.com Date: Mon, 25 Jan 2016 10:08:18 +0000 Message-Id: <1453716498-27238-1-git-send-email-dgilbert@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: jdenemar@redhat.com Subject: [Qemu-devel] [PATCH] use broadcast on qemu_pause_cond X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_HK_NAME_DR, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: "Dr. David Alan Gilbert" Jiri saw a hang on pause_all_vcpus called from postcopy_start, where the cpus are all apparently stopped ('stopped' flag set) but pause_all_vcpus is still stuck on a cond_wait on qemu_paused_cond. We suspect this is happening if a qmp_stop is called at about the same time as the postcopy code calls that pause_all_vcpus; although they both should have the main lock held, Paolo spotted the cond_wait unlocks the global lock so perhaps they both could end up waiting at the same time? Signed-off-by: Dr. David Alan Gilbert Reported-by: Jiri Denemark --- cpus.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/cpus.c b/cpus.c index 3efff6b..1e97cc4 100644 --- a/cpus.c +++ b/cpus.c @@ -986,7 +986,7 @@ static void qemu_wait_io_event_common(CPUState *cpu) if (cpu->stop) { cpu->stop = false; cpu->stopped = true; - qemu_cond_signal(&qemu_pause_cond); + qemu_cond_broadcast(&qemu_pause_cond); } flush_queued_work(cpu); cpu->thread_kicked = false; @@ -1396,7 +1396,7 @@ void cpu_stop_current(void) current_cpu->stop = false; current_cpu->stopped = true; cpu_exit(current_cpu); - qemu_cond_signal(&qemu_pause_cond); + qemu_cond_broadcast(&qemu_pause_cond); } }