On Wed, 2016-11-30 at 01:25 -0500, Song liwei wrote:
> From: Liwei Song <liwei.song@xxxxxxxxxxxxx>
>
> Fix the following Calltrace:
> [ 77.768221] WARNING: CPU: 5 PID: 645 at
> drivers/dma/dmaengine.c:1069 dma_async_device_unregister+0xe2/0xf0
> [ 77.775058] dma_async_device_unregister called while 1 clients hold
> a reference
> [ 77.825048] CPU: 5 PID: 645 Comm: sh Not tainted 4.8.8-
> WR9.0.0.0_standard+ #3
> [ 77.832550] Hardware name: Intel Corp. Aspen Cove/Server, BIOS
> HAVLCRB1.X64.0012.D58.1604140405 04/14/2016
> [ 77.840396] 0000000000000000 ffffc90008adbc80 ffffffff81403456
> ffffc90008adbcd0
> [ 77.848245] 0000000000000000 ffffc90008adbcc0 ffffffff8105e2e1
> 0000042d08adbf20
> [ 77.855934] ffff88046a861c18 ffff88046a85c420 ffffffff820d4200
> ffff88046ae92318
> [ 77.863601] Call Trace:
> [ 77.871113] [<ffffffff81403456>] dump_stack+0x4f/0x69
> [ 77.878655] [<ffffffff8105e2e1>] __warn+0xd1/0xf0
> [ 77.886102] [<ffffffff8105e34f>] warn_slowpath_fmt+0x4f/0x60
> [ 77.893508] [<ffffffff814187a9>] ? find_next_bit+0x19/0x20
> [ 77.900730] [<ffffffff814bf83e>] ?
> dma_channel_rebalance+0x23e/0x270
> [ 77.907814] [<ffffffff814bfee2>]
> dma_async_device_unregister+0xe2/0xf0
> [ 77.914992] [<ffffffff814c53aa>] hsu_dma_remove+0x1a/0x60
> [ 77.921977] [<ffffffff814ee14c>] dnv_exit+0x1c/0x20
> [ 77.928752] [<ffffffff814edff6>] mid8250_remove+0x26/0x40
> [ 77.935607] [<ffffffff8144f1b9>] pci_device_remove+0x39/0xc0
> [ 77.942292] [<ffffffff8160cfea>]
> __device_release_driver+0x9a/0x140
> [ 77.948836] [<ffffffff8160d0b3>] device_release_driver+0x23/0x30
> [ 77.955364] [<ffffffff81447dcc>] pci_stop_bus_device+0x8c/0xa0
> [ 77.961769] [<ffffffff81447f0a>]
> pci_stop_and_remove_bus_device_locked+0x1a/0x30
> [ 77.968113] [<ffffffff81450d4e>] remove_store+0x5e/0x70
> [ 77.974267] [<ffffffff81607ed8>] dev_attr_store+0x18/0x30
> [ 77.980243] [<ffffffff8123006a>] sysfs_kf_write+0x3a/0x50
> [ 77.986180] [<ffffffff8122f5ab>] kernfs_fop_write+0x10b/0x190
> [ 77.992118] [<ffffffff811bf1c8>] __vfs_write+0x18/0x40
> [ 77.998032] [<ffffffff811bfdee>] vfs_write+0xae/0x190
> [ 78.003747] [<ffffffff811c1016>] SyS_write+0x46/0xb0
> [ 78.009234] [<ffffffff81a4c31b>]
> entry_SYSCALL_64_fastpath+0x13/0x8f
> [ 78.014809] ---[ end trace 0c36dd73b7408eb2 ]---
>
> This happens when the 8250 serial controller is hotplugged as follows:
> echo 1 > /sys/bus/pci/devices/0000:00:1a.0/remove
>
> This trace happens due to the serial port still holding a reference
> when
> the dma device is unregistered.
> The dma unregister routine will check if there is still a reference
> exist,
> if so it will give the WARNING(here serial port still was not
> unregister).
>
> To fix this, We need to unregister the serial port first, then do DMA
> device unregister to make sure there is no reference when to DMA
> routine.
>
Good catch, thanks!
Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Liwei Song <liwei.song@xxxxxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_mid.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_mid.c
> b/drivers/tty/serial/8250/8250_mid.c
> index 39c2324..ac013edf 100644
> --- a/drivers/tty/serial/8250/8250_mid.c
> +++ b/drivers/tty/serial/8250/8250_mid.c
> @@ -303,10 +303,10 @@ static void mid8250_remove(struct pci_dev *pdev)
> {
> struct mid8250 *mid = pci_get_drvdata(pdev);
>
> + serial8250_unregister_port(mid->line);
> +
> if (mid->board->exit)
> mid->board->exit(mid);
> -
> - serial8250_unregister_port(mid->line);
> }
>
> static const struct mid8250_board pnw_board = {
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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