From 8f571bbfc621fd0826bbc7a8924c811f3a3167c9 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Mon, 6 Aug 2018 16:32:27 +0200
Subject: [PATCH] fbcon: Do not takeover the console from atomic context

Taking over the console involves allocating mem with GFP_KERNEL, talking
to drm drivers, etc. So this should not be done from an atomic context.

But the console-output trigger deferred console takeover may happen from an
atomic context, which leads to "BUG: sleeping function called from invalid
context" errors.

This commit fixes these errors by doing the deferred takeover from a
workqueue when the notifier runs from an atomic context.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/fbdev/core/fbcon.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index a3fd510..f812891 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -3596,7 +3596,22 @@ static int fbcon_init_device(void)
 }
 
 #ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
+static void fbcon_register_existing_fbs(struct work_struct *work)
+{
+	int i;
+
+	console_lock();
+
+	for (i = 0; i < FB_MAX; i++) {
+		if (registered_fb[i])
+			fbcon_fb_registered(registered_fb[i]);
+	}
+
+	console_unlock();
+}
+
 static struct notifier_block fbcon_output_nb;
+static DECLARE_WORK(fbcon_deferred_takeover_work, fbcon_register_existing_fbs);
 
 static int fbcon_output_notifier(struct notifier_block *nb,
 				 unsigned long action, void *data)
@@ -3611,10 +3626,8 @@ static int fbcon_output_notifier(struct notifier_block *nb,
 	deferred_takeover = false;
 	logo_shown = FBCON_LOGO_DONTSHOW;
 
-	for (i = 0; i < FB_MAX; i++) {
-		if (registered_fb[i])
-			fbcon_fb_registered(registered_fb[i]);
-	}
+	/* We may get called in atomic context */
+	schedule_work(&fbcon_deferred_takeover_work);
 
 	return NOTIFY_OK;
 }
-- 
2.18.0