b86b8eb6fe
ACM driver may accept data to transmit while system is not fully resumed. In this case ACM driver buffers data and prepare URBs on usb anchor list. There is a little chance that two tasks put a char and initiate acm_tty_flush_chars(). In such a case, driver will put one URB twice on usb anchor list. This patch also reset length of data before resue of a buffer. This not only prevent sending rubbish, but also lower risc of race. Without this patch we hit following kernel panic in one of our stabilty/stress tests. [ 46.884442] *list_add double add*: new=ffff9b2ab7289330, prev=ffff9b2ab7289330, next=ffff9b2ab81e28e0. [ 46.884476] Modules linked in: hci_uart btbcm bluetooth rfkill_gpio igb_avb(O) cfg80211 snd_soc_sst_bxt_tdf8532 snd_soc_skl snd_soc_skl_ipc snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_sst_acpi snd_soc_sst_match snd_hda_ext_core snd_hda_core trusty_timer trusty_wall trusty_log trusty_virtio trusty_ipc trusty_mem trusty_irq trusty virtio_ring virtio intel_ipu4_mmu_bxtB0 lib2600_mod_bxtB0 intel_ipu4_isys_mod_bxtB0 lib2600psys_mod_bxtB0 intel_ipu4_psys_mod_bxtB0 intel_ipu4_mod_bxtB0 intel_ipu4_wrapper_bxtB0 intel_ipu4_acpi videobuf2_dma_contig as3638 dw9714 lm3643 crlmodule smiapp smiapp_pll [ 46.884480] CPU: 1 PID: 33 Comm: kworker/u8:1 Tainted: G U W O 4.9.56-quilt-2e5dc0ac-g618ed69ced6e-dirty #4 [ 46.884489] Workqueue: events_unbound flush_to_ldisc [ 46.884494] ffffb98ac012bb08 ffffffffad3e82e5 ffffb98ac012bb58 0000000000000000 [ 46.884497] ffffb98ac012bb48 ffffffffad0a23d1 00000024ad6374dd ffff9b2ab7289330 [ 46.884500] ffff9b2ab81e28e0 ffff9b2ab7289330 0000000000000002 0000000000000000 [ 46.884501] Call Trace: [ 46.884507] [<ffffffffad3e82e5>] dump_stack+0x67/0x92 [ 46.884511] [<ffffffffad0a23d1>] __warn+0xd1/0xf0 [ 46.884513] [<ffffffffad0a244f>] warn_slowpath_fmt+0x5f/0x80 [ 46.884516] [<ffffffffad407443>] __list_add+0xb3/0xc0 [ 46.884521] [<ffffffffad71133c>] *usb_anchor_urb*+0x4c/0xa0 [ 46.884524] [<ffffffffad782c6f>] *acm_tty_flush_chars*+0x8f/0xb0 [ 46.884527] [<ffffffffad782cd1>] *acm_tty_put_char*+0x41/0x100 [ 46.884530] [<ffffffffad4ced34>] tty_put_char+0x24/0x40 [ 46.884533] [<ffffffffad4d3bf5>] do_output_char+0xa5/0x200 [ 46.884535] [<ffffffffad4d3e98>] __process_echoes+0x148/0x290 [ 46.884538] [<ffffffffad4d654c>] n_tty_receive_buf_common+0x57c/0xb00 [ 46.884541] [<ffffffffad4d6ae4>] n_tty_receive_buf2+0x14/0x20 [ 46.884543] [<ffffffffad4d9662>] tty_ldisc_receive_buf+0x22/0x50 [ 46.884545] [<ffffffffad4d9c05>] flush_to_ldisc+0xc5/0xe0 [ 46.884549] [<ffffffffad0bcfe8>] process_one_work+0x148/0x440 [ 46.884551] [<ffffffffad0bdc19>] worker_thread+0x69/0x4a0 [ 46.884554] [<ffffffffad0bdbb0>] ? max_active_store+0x80/0x80 [ 46.884556] [<ffffffffad0c2e10>] kthread+0x110/0x130 [ 46.884559] [<ffffffffad0c2d00>] ? kthread_park+0x60/0x60 [ 46.884563] [<ffffffffadad9917>] ret_from_fork+0x27/0x40 [ 46.884566] ---[ end trace 3bd599058b8a9eb3 ]--- Signed-off-by: Dominik Bozek <dominikx.bozek@intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> Acked-by: Oliver Neukum <oneukum@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.