Patch "fbcon: set a default value to blink interval" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

fbcon: set a default value to blink interval

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fbcon-set-a-default-value-to-blink-interval.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jean-Philippe Brucker <[email protected]>
Date: Mon, 15 Feb 2016 18:41:33 +0000
Subject: fbcon: set a default value to blink interval

From: Jean-Philippe Brucker <[email protected]>

commit a1e533ec07d583d01349ef13c0c965b8633e1b91 upstream.

Since commit 27a4c827c34ac4256a190cc9d24607f953c1c459
fbcon: use the cursor blink interval provided by vt

two attempts have been made at fixing a possible hang caused by cursor_timer_handler. That function registers a timer to be triggered at "jiffies + fbcon_ops.cur_blink_jiffies".

A new case had been encountered during initialisation of clcd-pl11x:

    fbcon_fb_registered
    do_fbcon_takeover

    ->  do_register_con_driver
        fbcon_startup
    (A) add_cursor_timer (with cur_blink_jiffies = 0)

    ->  do_bind_con_driver
        visual_init
        fbcon_init
    (B) cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);

If we take an softirq anywhere between A and B (and we do), cursor_timer_handler executes indefinitely.

Instead of patching all possible paths that lead to this case one at a time, fix the issue at the source and initialise cur_blink_jiffies to 200ms when allocating fbcon_ops. This was its default value before aforesaid commit. fbcon_cursor or fbcon_init will refine this value downstream.

---
 drivers/video/console/fbcon.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -709,6 +709,7 @@ static int con2fb_acquire_newinfo(struct
 	}
 
 	if (!err) {
+		ops->cur_blink_jiffies = HZ / 5;
 		info->fbcon_par = ops;
 
 		if (vc)

@@ -956,6 +957,7 @@ static const char *fbcon_startup(void)
 	ops->currcon = -1;
 	ops->graphics = 1;
 	ops->cur_rotate = -1;
+	ops->cur_blink_jiffies = HZ / 5;
 	info->fbcon_par = ops;
 	p->con_rotate = initial_rotation;
 	set_blitting_type(vc, info);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/fbcon-set-a-default-value-to-blink-interval.patch