Commit 1b647823 authored Jul 02, 2014 by David Vrabel

xen/manage: fix potential deadlock when resuming the console



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 <david.vrabel@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: <stable@vger.kernel.org>

parent 13cd36a3

drivers/xen/manage.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -88,7 +88,6 @@ static int xen_suspend(void *data)

		if (!si->cancelled) {
		xen_irq_resume();
		xen_console_resume();
		xen_timer_resume();
		}

		@@ -135,6 +134,10 @@ 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();

		raw_notifier_call_chain(&xen_resume_notifier, 0, NULL);

		dpm_resume_start(si.cancelled ? PMSG_THAW : PMSG_RESTORE);