On 2018-10-22 10:59, Sean Young wrote:
On Sat, Oct 20, 2018 at 11:12:16PM +0200, Hans Verkuil wrote:
Hi Sean,
Can you take a look at this, it appears to be an RC issue, see my analysis below.
On 10/20/2018 03:26 PM, Torbjorn Jansson wrote:
Hello
i'm using the pulse8 usb cec adapter to control my tv.
i have a few scripts that poll the power status of my tv and after a while it stops working returning errors when trying to check if tv is on or off.
this i think matches a kernel oops i'm seeing that i suspect is related to this.
i have sometimes been able to recover from this problem by completely cutting power to my tv and also unplugging the usb cec adapter.
i have a feeling that the tv is at least partly to blame for cec-ctl not working but in any case there shouldn't be a kernel oops.
also every now and then i see this in dmesg:
cec cec0: transmit: failed 05
cec cec0: transmit: failed 06
but that doesn't appear to do any harm as far as i can tell.
any idea whats causing the oops?
the ops:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 9 PID: 27687 Comm: kworker/9:2 Tainted: P OE 4.18.12-200.fc28.x86_64 #1
Hardware name: Supermicro C7X99-OCE-F/C7X99-OCE-F, BIOS 2.1a 06/15/2018
Workqueue: events pulse8_irq_work_handler [pulse8_cec]
RIP: 0010:ir_lirc_scancode_event+0x3d/0xb0 [rc_core]
Huh. ir_lirc_scancode_event() calls spin_lock_irqsave(&dev->lirc_fh_lock, flags);
The spinlock dev->lirc_fh_lock is initialized in ir_lirc_register(), which is called
from rc_register_device(), except when the protocol is CEC:
/* Ensure that the lirc kfifo is setup before we start the thread */
if (dev->allowed_protocols != RC_PROTO_BIT_CEC) {
rc = ir_lirc_register(dev);
if (rc < 0)
goto out_rx;
}
So it looks like ir_lirc_scancode_event() fails because dev->lirc_fh_lock was never
initialized.
Could this be fall-out from the lirc changes you did not too long ago?
Yes, this is broken. My bad, sorry. I think this must have been broken since
v4.16. I can write a patch but I don't have a patch but I'm on the train
to ELCE in Edinburgh now, with no hardware to test on.
Sean
the kernel oops have been happening for a while now.
yesterday when i checked my logs i can see them at least back a couple of
months when i was running 4.17
also my scripts to poll status of my tv and turn it on/off works for a while so
it doesn't crash right away.
maybe it only crashes when i send cec command to turn on/off tv and only
polling for status is no problem.
i think i have a separate issue too because i had problems even before the
kernel oopses started.
but i suspect this is caused by my tv locking up the cec bus because unplugging
power to tv for a few minutes (i must wait or it will still be just as broken)
and then back used to resolve the cec errors from my scripts.
