On Mon, Oct 22, 2018 at 12:30:29PM +0100, Hans Verkuil wrote:
> On 10/22/2018 11:14 AM, Sean Young wrote:
> > On Mon, Oct 22, 2018 at 11:44:22AM +0200, Torbjorn Jansson wrote:
> >> 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.
> >
> >
> > Would you be able to test the following patch please?
>
> Sean,
>
> I think you should be able to test this with the vivid driver. Load the vivid driver,
> run:
>
> cec-ctl --tv; cec-ctl -d1 --playback
>
> Then:
>
> cec-ctl -d1 -t0 --user-control-pressed ui-cmd=F5
Ah, thanks. That will help with testing/reproducing.
> That said, I tried this, but it doesn't crash for me, but perhaps I need to run
> some RC command first...
Hmm I think those commands should be enough. It probably needs
CONFIG_DEBUG_SPINLOCK to detect the uninitialized spinlock. I'm trying it now.
Thanks,
Sean
