From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753266AbaHDQx7 (ORCPT ); Mon, 4 Aug 2014 12:53:59 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:56650 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752203AbaHDQt5 (ORCPT ); Mon, 4 Aug 2014 12:49:57 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Boris Ostrovsky" , "David Vrabel" Date: Mon, 04 Aug 2014 17:48:31 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 21/94] xen/manage: fix potential deadlock when resuming the console In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: David Vrabel commit 1b6478231c6f5f844185acb32045cf195028cfce upstream. Calling xen_console_resume() in xen_suspend() causes a warning because it locks irq_mapping_update_lock (a mutex) and this may sleep. If a userspace process is using the evtchn device then this mutex may be locked at the point of the stop_machine() call and xen_console_resume() would then deadlock. Resuming the console after stop_machine() returns avoids this deadlock. Signed-off-by: David Vrabel Reviewed-by: Boris Ostrovsky [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/xen/manage.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/xen/manage.c +++ b/drivers/xen/manage.c @@ -93,7 +93,6 @@ static int xen_suspend(void *data) if (!si->cancelled) { xen_irq_resume(); - xen_console_resume(); xen_timer_resume(); } @@ -149,6 +148,10 @@ static void do_suspend(void) err = stop_machine(xen_suspend, &si, cpumask_of(0)); + /* Resume console as early as possible. */ + if (!si.cancelled) + xen_console_resume(); + dpm_resume_noirq(si.cancelled ? PMSG_THAW : PMSG_RESTORE); if (err) {