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

Scot Doyle
2016-05-19T04:21:53Z

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@scotdoyle.com>
Cc: <stable@vger.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