Subject: [PATCH 0/4] qmi_wwan: fix QMAP handling

From: Reinhard Speyerer <[email-masked]>
Date: Wed, 12 Jun 2019 19:01:44 +0200

This series addresses the following issues observed when using the
QMAP support of the qmi_wwan driver:

1. The QMAP code in the qmi_wwan driver is based on the CodeAurora
   GobiNet driver ([1], [2]) which does not process QMAP padding
   in the RX path correctly. This causes qmimux_rx_fixup() to pass
   incorrect data to the IP stack when padding is used.

2. qmimux devices currently lack proper network device usage statistics.

3. RCU stalls on device disconnect with QMAP activated like this

   # echo Y > /sys/class/net/wwan0/qmi/raw_ip 
   # echo 1 > /sys/class/net/wwan0/qmi/add_mux
   # echo 2 > /sys/class/net/wwan0/qmi/add_mux
   # echo 3 > /sys/class/net/wwan0/qmi/add_mux

   have been observed in certain setups:

   [ 2273.676593] option1 ttyUSB16: GSM modem (1-port) converter now disconnected from ttyUSB16
   [ 2273.676617] option 6-1.2:1.0: device disconnected
   [ 2273.676774] WARNING: CPU: 1 PID: 141 at kernel/rcu/tree_plugin.h:342 rcu_note_context_switch+0x2a/0x3d0
   [ 2273.676776] Modules linked in: option qmi_wwan cdc_mbim cdc_ncm qcserial cdc_wdm usb_wwan sierra sierra_net usbnet mii edd coretemp iptable_mangle ip6_tables iptable_filter ip_tables cdc_acm dm_mod dax iTCO_wdt evdev iTCO_vendor_support sg ftdi_sio usbserial e1000e ptp pps_core i2c_i801 ehci_pci button lpc_ich i2c_core mfd_core uhci_hcd ehci_hcd rtc_cmos usbcore usb_common sd_mod fan ata_piix thermal
   [ 2273.676817] CPU: 1 PID: 141 Comm: kworker/1:1 Not tainted 4.19.38-rsp-1 #1
   [ 2273.676819] Hardware name: Not Applicable   Not Applicable  /CX-GS/GM45-GL40             , BIOS V1.11      03/23/2011
   [ 2273.676828] Workqueue: usb_hub_wq hub_event [usbcore]
   [ 2273.676832] EIP: rcu_note_context_switch+0x2a/0x3d0
   [ 2273.676834] Code: 55 89 e5 57 56 89 c6 53 83 ec 14 89 45 f0 e8 5d ff ff ff 89 f0 64 8b 3d 24 a6 86 c0 84 c0 8b 87 04 02 00 00 75 7a 85 c0 7e 7a <0f> 0b 80 bf 08 02 00 00 00 0f 84 87 00 00 00 e8 b2 e2 ff ff bb dc
   [ 2273.676836] EAX: 00000001 EBX: f614bc00 ECX: 00000001 EDX: c0715b81
   [ 2273.676838] ESI: 00000000 EDI: f18beb40 EBP: f1a3dc20 ESP: f1a3dc00
   [ 2273.676840] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010002
   [ 2273.676842] CR0: 80050033 CR2: b7e97230 CR3: 2f9c4000 CR4: 000406b0
   [ 2273.676843] Call Trace:
   [ 2273.676847]  ? preempt_count_add+0xa5/0xc0
   [ 2273.676852]  __schedule+0x4e/0x4f0
   [ 2273.676855]  ? __queue_work+0xf1/0x2a0
   [ 2273.676858]  ? _raw_spin_lock_irqsave+0x14/0x40
   [ 2273.676860]  ? preempt_count_add+0x52/0xc0
   [ 2273.676862]  schedule+0x33/0x80
   [ 2273.676865]  _synchronize_rcu_expedited+0x24e/0x280
   [ 2273.676867]  ? rcu_accelerate_cbs_unlocked+0x70/0x70
   [ 2273.676871]  ? wait_woken+0x70/0x70
   [ 2273.676873]  ? rcu_accelerate_cbs_unlocked+0x70/0x70
   [ 2273.676875]  ? _synchronize_rcu_expedited+0x280/0x280
   [ 2273.676877]  synchronize_rcu_expedited+0x22/0x30
   [ 2273.676881]  synchronize_net+0x25/0x30
   [ 2273.676885]  dev_deactivate_many+0x133/0x230
   [ 2273.676887]  ? preempt_count_add+0xa5/0xc0
   [ 2273.676890]  __dev_close_many+0x4d/0xc0
   [ 2273.676892]  ? skb_dequeue+0x40/0x50
   [ 2273.676895]  dev_close_many+0x5d/0xd0
   [ 2273.676898]  rollback_registered_many+0xbf/0x4c0
   [ 2273.676901]  ? raw_notifier_call_chain+0x1a/0x20
   [ 2273.676904]  ? call_netdevice_notifiers_info+0x23/0x60
   [ 2273.676906]  ? netdev_master_upper_dev_get+0xe/0x70
   [ 2273.676908]  rollback_registered+0x1f/0x30
   [ 2273.676911]  unregister_netdevice_queue+0x47/0xb0
   [ 2273.676915]  qmimux_unregister_device+0x1f/0x30 [qmi_wwan]
   [ 2273.676917]  qmi_wwan_disconnect+0x5d/0x90 [qmi_wwan]
   ...
   [ 2273.677001] ---[ end trace 0fcc5f88496b485a ]---
   [ 2294.679136] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
   [ 2294.679140] rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P141
   [ 2294.679144] rcu: 	(detected by 0, t=21002 jiffies, g=265857, q=8446)
   [ 2294.679148] kworker/1:1     D    0   141      2 0x80000000

In addition the permitted QMAP mux_id value range is extended for
compatibility with ip(8) and the rmnet driver.

Reinhard

[1]: https://portland.source.codeaurora.org/patches/quic/gobi
[2]: https://portland.source.codeaurora.org/quic/qsdk/oss/lklm/gobinet/

Reinhard Speyerer (4):
  qmi_wwan: add support for QMAP padding in the RX path
  qmi_wwan: add network device usage statistics for qmimux devices
  qmi_wwan: avoid RCU stalls on device disconnect when in QMAP mode
  qmi_wwan: extend permitted QMAP mux_id value range

 Documentation/ABI/testing/sysfs-class-net-qmi |   4 +-
 drivers/net/usb/qmi_wwan.c                    | 103 ++++++++++++++++++++++----
 2 files changed, 91 insertions(+), 16 deletions(-)

-- 
2.11.0