Re: [PATCH 0/6] Clean up the sdio_uart driver and fix the tty code

From: Nicolas Pitre
Date: Mon Nov 02 2009 - 19:30:40 EST

On Mon, 2 Nov 2009, Nicolas Pitre wrote:

> With this folded in, the card does work with the full series applied.
> However the kernel is now crashing when the card is pulled out while
> some process is reading from the device. This used to behave well
> before. I don't have time to investigate that one right now though.

OK, here more data points:

My test is to insert GPS card and do a 'cat /dev/ttySDIO0' and watch
NMEA data scrolling by.

With "sdio_uart: Move the open lock" applied, I can pull the card out
and the cat process terminates. However inserting the card back and
repeating the test again always gives me:

cat: /dev/ttySDIO0: Input/output error

until I reboot. Same thing happens if I terminates cat with ^C and
start it again.

With "sdio_uart: Switch to the open/close helpers" applied, things got
even worse. Interrupting cat with ^C still gives the same result as
above. But yanking the card out when cat is still running doesn't
terminate cat unless I ^C it at which point the kernel crashes with a
BUG(). The backtrace is:

[<c0029c88>] (__bug+0x18/0x24) from [<c02665d0>] (sdio_writeb+0x1c/0x4c)
[<c02665d0>] (sdio_writeb+0x1c/0x4c) from [<c01b4098>] (tty_port_lower_dtr_rts+0x1c/0x20)
[<c01b4098>] (tty_port_lower_dtr_rts+0x1c/0x20) from [<c01b412c>] (tty_port_close_end+0x2c/0x130)
[<c01b412c>] (tty_port_close_end+0x2c/0x130) from [<c01b49a8>] (tty_port_close+0x2c/0x3c)
[<c01b49a8>] (tty_port_close+0x2c/0x3c) from [<c01ae0c4>] (tty_release_dev+0x17c/0x478)
[<c01ae0c4>] (tty_release_dev+0x17c/0x478) from [<c01ae3e8>] (tty_release+0x28/0x4c)
[<c01ae3e8>] (tty_release+0x28/0x4c) from [<c00b5bf0>] (__fput+0x118/0x210)
[<c00b5bf0>] (__fput+0x118/0x210) from [<c00b28b4>] (filp_close+0x70/0x7c)
[<c00b28b4>] (filp_close+0x70/0x7c) from [<c003d0e0>] (put_files_struct+0x80/0xd4)
[<c003d0e0>] (put_files_struct+0x80/0xd4) from [<c003eac0>] (do_exit+0x220/0x714)
[<c003eac0>] (do_exit+0x220/0x714) from [<c003f074>] (do_group_exit+0xc0/0xf4)
[<c003f074>] (do_group_exit+0xc0/0xf4) from [<c004d8d0>] (get_signal_to_deliver+0x3c8/0x428)
[...] (impressive nesting culled)

Only after backing out those 2 patches as wellas "sdio_uart: refcount
the tty objects" is the correct behavior restored.


[<c004d8d0>] (get_signal_to_deliver+0x3c8/0x428) from [<c0028b34>] (do_notify_resume+0x5c/0x5d0)
[<c0028b34>] (do_notify_resume+0x5c/0x5d0) from [<c0026a88>] (work_pending+0x1c/0x20)

> Nicolas
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