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Date:   Sat, 13 Jul 2019 23:08:53 +0200
From:   Ladislav Michl <ladis@linux-mips.org>
To:     linux-usb@vger.kernel.org, linux-serial@vger.kernel.org
Cc:     Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= <mirq-linux@rere.qmqm.pl>
Subject: [PATCH v2 0/5] usb: gadget: u_serial: Fix and cleanup
Message-ID: <20190713210853.GA25753@lenoch>
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Following patchset makes console work (patch 1 and 4) for an AT91SAM9G20
board connected to xhci_hcd and does some cleanup.
Tested with "console=ttyS0,115200n8 console=ttyGS0" on kernel command line
and following inittab:
console::respawn:/sbin/getty -L 115200 ttyS0 vt100
console::respawn:/sbin/getty -L 115200 ttyGS0 vt100

However there is an issue remaining:
Disconnect triggers WARN_ON in gs_close:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 501 at drivers/usb/gadget/function/u_serial.c:706 gs_close+0x3c/0x1e4
Modules linked in:
CPU: 0 PID: 501 Comm: getty Not tainted 5.2.0-rc7 #44
Hardware name: Atmel AT91SAM9
[<c0107514>] (unwind_backtrace) from [<c01051c0>] (show_stack+0x10/0x18)
[<c01051c0>] (show_stack) from [<c05465a8>] (dump_stack+0x18/0x24)
[<c05465a8>] (dump_stack) from [<c010fa80>] (__warn+0xcc/0xe4)
[<c010fa80>] (__warn) from [<c010fad0>] (warn_slowpath_null+0x38/0x48)
[<c010fad0>] (warn_slowpath_null) from [<c03b6648>] (gs_close+0x3c/0x1e4)
[<c03b6648>] (gs_close) from [<c03036b0>] (tty_release+0x1d4/0x460)
[<c03036b0>] (tty_release) from [<c01ce464>] (__fput+0xe4/0x1b0)
[<c01ce464>] (__fput) from [<c0124e1c>] (task_work_run+0x8c/0xa8)
[<c0124e1c>] (task_work_run) from [<c011155c>] (do_exit+0x354/0x814)
[<c011155c>] (do_exit) from [<c0111a9c>] (do_group_exit+0x54/0xb8)
[<c0111a9c>] (do_group_exit) from [<c011a190>] (get_signal+0x18c/0x658)
[<c011a190>] (get_signal) from [<c0104bbc>] (do_work_pending+0xe0/0x44c)
[<c0104bbc>] (do_work_pending) from [<c0101068>] (slow_work_pending+0xc/0x20)
Exception stack(0xc3797fb0 to 0xc3797ff8)
7fa0:                                     00000000 beb87d0c 00000001 00000000
7fc0: 0009a150 00000000 00099c04 00000003 0009a198 0007e049 00099bd4 0009a1e4
7fe0: b6e3f000 beb87cd8 00018210 b6dbcc40 60000010 00000000
---[ end trace 70af570fde0de49b ]---

Explanation lives in drivers/tty/serial/ip22zilog.c at line 751 (see also
__tty_hangup), but naive approach adding
	if (test_bit(TTY_HUPPING, &tty->flags))
		return 0;
at the beginning of gs_close does not work as this way port->port.count
never drops back to zero. Ideas welcome.

Btw, it would seem nicer to have single output kfifo for both kernel
console and tty, but that involves greater changes and I'd like to have
driver working in stable as well. 

Changes:
- v2: Fixed locking, patches splitted, starving write fixed.

Ladislav Michl (5):
  usb: gadget: u_serial: Fix console_req complete event race
  usb: gadget: u_serial: Remove console specific alloc/free req
    functions
  usb: gadget: u_serial: Fix console_req access race
  usb: gadget: u_serial: Fix starving write
  usb: gadget: u_serial: Use bool for req_busy

 drivers/usb/gadget/function/u_serial.c | 120 +++++++++++--------------
 1 file changed, 51 insertions(+), 69 deletions(-)

-- 
2.22.0