[PATCH] media: rc: cec devices do not have a lirc chardev

[Sean Young <sean@mess.org>]

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?

Thanks,

Sean
---
>From 1b8b20b606b30c0e301c80e18af8d77194269bc1 Mon Sep 17 00:00:00 2001
From: Sean Young <sean@mess.org>
Date: Mon, 22 Oct 2018 10:01:50 +0100
Subject: [PATCH] media: rc: cec devices do not have a lirc chardev
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This fixes an oops in ir_lirc_scancode_event().

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]
Code: 8d ae b4 07 00 00 49 81 c6 b8 07 00 00 53 e8 4a df c3 d5 48 89 ef 49 89 45 00 e8 4e 84 41 d6 49 8b 1e 49 89 c4 4c 39 f3 74 58 <8b> 43 38 8b 53 40 89 c1 2b 4b 3c 39 ca 72 41 21 d0 49 8b 7d 00 49
RSP: 0018:ffffaa10e3c07d58 EFLAGS: 00010017
RAX: 0000000000000002 RBX: 0000000000000000 RCX: 0000000000000018
RDX: 0000000000000001 RSI: 00316245397fa93c RDI: ffff966d31c8d7b4
RBP: ffff966d31c8d7b4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: ffffaa10e3c07e28 R12: 0000000000000002
R13: ffffaa10e3c07d88 R14: ffff966d31c8d7b8 R15: 0000000000000073
FS:  0000000000000000(0000) GS:ffff966d3f440000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000038 CR3: 00000009d820a003 CR4: 00000000003606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ir_do_keydown+0x75/0x260 [rc_core]
 rc_keydown+0x54/0xc0 [rc_core]
 cec_received_msg_ts+0xaa8/0xaf0 [cec]
 process_one_work+0x1a1/0x350
 worker_thread+0x30/0x380
 ? pwq_unbound_release_workfn+0xd0/0xd0
 kthread+0x112/0x130
 ? kthread_create_worker_on_cpu+0x70/0x70
 ret_from_fork+0x35/0x40
Modules linked in: rc_tt_1500 dvb_usb_dvbsky dvb_usb_v2 uas usb_storage fuse vhost_net vhost tap xt_CHECKSUM iptable_mangle ip6t_REJECT nf_reject_ipv6 tun 8021q garp mrp xt_nat macvlan xfs devlink ebta
 si2157 si2168 cx25840 cx23885 kvm altera_ci tda18271 joydev ir_rc6_decoder rc_rc6_mce crct10dif_pclmul crc32_pclmul ghash_clmulni_intel intel_cstate intel_uncore altera_stapl m88ds3103 tveeprom cx2341
 mxm_wmi igb crc32c_intel megaraid_sas dca i2c_algo_bit wmi vfio_pci irqbypass vfio_virqfd vfio_iommu_type1 vfio i2c_dev
CR2: 0000000000000038

Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: Sean Young <sean@mess.org>
---
 drivers/media/rc/rc-main.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index 552bbe82a160..877978dbd409 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -695,7 +695,8 @@ void rc_repeat(struct rc_dev *dev)
 			 (dev->last_toggle ? LIRC_SCANCODE_FLAG_TOGGLE : 0)
 	};
 
-	ir_lirc_scancode_event(dev, &sc);
+	if (dev->allowed_protocols != RC_PROTO_BIT_CEC)
+		ir_lirc_scancode_event(dev, &sc);
 
 	spin_lock_irqsave(&dev->keylock, flags);
 
@@ -735,7 +736,8 @@ static void ir_do_keydown(struct rc_dev *dev, enum rc_proto protocol,
 		.keycode = keycode
 	};
 
-	ir_lirc_scancode_event(dev, &sc);
+	if (dev->allowed_protocols != RC_PROTO_BIT_CEC)
+		ir_lirc_scancode_event(dev, &sc);
 
 	if (new_event && dev->keypressed)
 		ir_do_keyup(dev, false);
-- 
2.17.2