linux-kernel - [PATCH] fbcon: use default if cursor blink interval is not valid

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Date:	Wed, 18 May 2016 23:21:53 -0500 (CDT)
From:	Scot Doyle <lkml14@...tdoyle.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
cc:	David Daney <david.daney@...ium.com>,
	Ming Lei <ming.lei@...onical.com>,
	Dann Frazier <dann.frazier@...onical.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Pavel Machek <pavel@....cz>, Jonathan Liu <net147@...il.com>,
	Alistair Popple <alistair@...ple.id.au>,
	Jean-Philippe Brucker <jean-philippe.brucker@....com>,
	"Chintakuntla, Radha" <Radha.Chintakuntla@...iumnetworks.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, David Airlie <airlied@...ux.ie>,
	ddaney.cavm@...il.com, lkml14@...tdoyle.com,
	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] fbcon: use default if cursor blink interval is not valid

Two current [1] and three previous [2] systems locked during boot
because the cursor flash timer was set using an ops->cur_blink_jiffies
value of 0. Previous patches attempted to solve the problem by moving
variable initialization earlier in the setup sequence [2].

Use the normal cursor blink default interval of 200 ms if
ops->cur_blink_jiffies is not in the range specified in commit
bd63364caa8d. Since invalid values are not used, specific system
initialization timings should not cause lockups.

[1] https://bugs.launchpad.net/bugs/1574814
[2] see commits: 2a17d7e80f1d, f235f664a8af, a1e533ec07d5

Signed-off-by: Scot Doyle <lkml14@...tdoyle.com>
Cc: <stable@...r.kernel.org> [v4.2]
---
 drivers/video/console/fbcon.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 6e92917..da61d87 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -396,13 +396,23 @@ static void fb_flashcursor(struct work_struct *work)
 	console_unlock();
 }
 
+static int cursor_blink_jiffies(int candidate)
+{
+	if (candidate >= msecs_to_jiffies(50) &&
+	    candidate <= msecs_to_jiffies(USHRT_MAX))
+		return candidate;
+	else
+		return HZ / 5;
+}
+
 static void cursor_timer_handler(unsigned long dev_addr)
 {
 	struct fb_info *info = (struct fb_info *) dev_addr;
 	struct fbcon_ops *ops = info->fbcon_par;
 
 	queue_work(system_power_efficient_wq, &info->queue);
-	mod_timer(&ops->cursor_timer, jiffies + ops->cur_blink_jiffies);
+	mod_timer(&ops->cursor_timer, jiffies +
+	    cursor_blink_jiffies(ops->cur_blink_jiffies));
 }
 
 static void fbcon_add_cursor_timer(struct fb_info *info)
@@ -417,7 +427,8 @@ static void fbcon_add_cursor_timer(struct fb_info *info)
 
 		init_timer(&ops->cursor_timer);
 		ops->cursor_timer.function = cursor_timer_handler;
-		ops->cursor_timer.expires = jiffies + ops->cur_blink_jiffies;
+		ops->cursor_timer.expires = jiffies +
+		    cursor_blink_jiffies(ops->cur_blink_jiffies);
 		ops->cursor_timer.data = (unsigned long ) info;
 		add_timer(&ops->cursor_timer);
 		ops->flags |= FBCON_FLAGS_CURSOR_TIMER;
@@ -709,7 +720,6 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
 	}
 
 	if (!err) {
-		ops->cur_blink_jiffies = HZ / 5;
 		info->fbcon_par = ops;
 
 		if (vc)
@@ -957,7 +967,6 @@ 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);
-- 
2.1.4