xen: improve error handling in do_suspend.

The existing error handling has a few issues:
- If freeze_processes() fails it exits with shutting_down = SHUTDOWN_SUSPEND.
- If dpm_suspend_noirq() fails it exits without resuming xenbus.
- If stop_machine() fails it exits without resuming xenbus or calling
  dpm_resume_end().
- xs_suspend()/xs_resume() and dpm_suspend_noirq()/dpm_resume_noirq() were not
  nested in the obvious way.

Fix by ensuring each failure case goto's the correct label. Treat a failure of
stop_machine() as a cancelled suspend in order to follow the correct resume
path.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>

drivers/xen/manage.c

@@ -86,32 +86,32 @@ static void do_suspend(void)
 	err = freeze_processes();
 	if (err) {
 		printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
-		return;
+		goto out;
 	}
 #endif
 
 	err = dpm_suspend_start(PMSG_SUSPEND);
 	if (err) {
 		printk(KERN_ERR "xen suspend: dpm_suspend_start %d\n", err);
-		goto out;
+		goto out_thaw;
 	}
 
-	printk(KERN_DEBUG "suspending xenstore...\n");
-	xs_suspend();
-
 	err = dpm_suspend_noirq(PMSG_SUSPEND);
 	if (err) {
 		printk(KERN_ERR "dpm_suspend_noirq failed: %d\n", err);
-		goto resume_devices;
+		goto out_resume;
 	}
 
+	printk(KERN_DEBUG "suspending xenstore...\n");
+	xs_suspend();
+
 	err = stop_machine(xen_suspend, &cancelled, cpumask_of(0));
 
 	dpm_resume_noirq(PMSG_RESUME);
 
 	if (err) {
 		printk(KERN_ERR "failed to start xen_suspend: %d\n", err);
-		goto out;
+		cancelled = 1;
 	}
 
 	if (!cancelled) {
@@ -120,15 +120,17 @@ static void do_suspend(void)
 	} else
 		xs_suspend_cancel();
 
-resume_devices:
+out_resume:
 	dpm_resume_end(PMSG_RESUME);
 
 	/* Make sure timer events get retriggered on all CPUs */
 	clock_was_set();
-out:
+
+out_thaw:
 #ifdef CONFIG_PREEMPT
 	thaw_processes();
 #endif
+out:
 	shutting_down = SHUTDOWN_INVALID;
 }
 #endif	/* CONFIG_PM_SLEEP */