[PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer.

David Daney
2016-05-17T18:41:14Z

From: David Daney <david.daney@cavium.com>

We are getting somewhat random soft lockups with this signature:

[ 86.992215] [<fffffc00080935e0>] el1_irq+0xa0/0x10c
[ 86.997082] [<fffffc000841822c>] cursor_timer_handler+0x30/0x54
[ 87.002991] [<fffffc000810ec44>] call_timer_fn+0x54/0x1a8
[ 87.008378] [<fffffc000810ef88>] run_timer_softirq+0x1c4/0x2bc
[ 87.014200] [<fffffc000809077c>] __do_softirq+0x114/0x344
[ 87.019590] [<fffffc00080af45c>] irq_exit+0x74/0x98
[ 87.024458] [<fffffc00080fac20>] __handle_domain_irq+0x98/0xfc
[ 87.030278] [<fffffc000809056c>] gic_handle_irq+0x94/0x190

This is caused by the vt visual_init() function calling into
fbcon_init() with a vc_cur_blink_ms value of zero. This is a
transient condition, as it is later set to a non-zero value. But, if
the timer happens to expire while the blink rate is zero, it goes into
an endless loop, and we get soft lockup.

The fix is to initialize vc_cur_blink_ms before calling the con_init()
function.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: stable@vger.kernel.org
---
drivers/tty/vt/vt.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3e3c757..eef5c36 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -750,6 +750,7 @@ static void visual_init(struct vc_data *vc, int num, int init)
vc->vc_complement_mask = 0;
vc->vc_can_do_color = 0;
vc->vc_panic_force_write = false;
+ vc->vc_cur_blink_ms = DEFAULT_CURSOR_BLINK_MS;
vc->vc_sw->con_init(vc, init);
if (!vc->vc_complement_mask)
vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
--
1.8.3.1