On Mon, Feb 12, 2018 at 12:15:03PM -0800, sathyanarayan.kuppuswamy@xxxxxxxxxxxxxxx wrote: > From: Dominik Bozek <dominikx.bozek@xxxxxxxxx> > > 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: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@xxxxxxxxx> Why hasn't the author of this patch signed off on it? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
