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e359a4e38d
Since at least before 2.6.30, it has not been possible to observe
a hung up file pointer in a tty driver's open() method unless/until
the driver open() releases the tty_lock() (eg., before blocking).
This is because tty_open() adds the file pointer while holding
the tty_lock() _and_ doesn't release the lock until after calling
the tty driver's open() method. [ Before tty_lock(), this was
lock_kernel(). ]
Since __tty_hangup() first waits on the tty_lock() before
enumerating and hanging up the open file pointers, either
__tty_hangup() will wait for the tty_lock() or tty_open() will
not yet have added the file pointer. For example,
CPU 0 | CPU 1
|
tty_open | __tty_hangup
.. | ..
tty_lock | ..
tty_reopen | tty_lock / blocks
.. |
tty_add_file(tty, filp) |
.. |
tty->ops->open(tty, filp) |
tty_port_open |
tty_port_block_til_ready |
.. |
while (1) |
.. |
tty_unlock | / unblocks
schedule | for each filp on tty->tty_files
| f_ops = tty_hung_up_fops;
| ..
| tty_unlock
tty_lock |
.. |
tty_unlock |
Note that since tty_port_block_til_ready() and similar drop
the tty_lock while blocking, when woken, the file pointer
must then be tested for having been hung up.
Also, fix bit-rotted drivers that used extra_count to track the
port->count bump.
CC: Mikael Starvik <starvik@axis.com>
CC: Samuel Ortiz <samuel@sortiz.org>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| .. | ||
| agp | ||
| hw_random | ||
| ipmi | ||
| mwave | ||
| pcmcia | ||
| tpm | ||
| xilinx_hwicap | ||
| apm-emulation.c | ||
| applicom.c | ||
| applicom.h | ||
| bfin-otp.c | ||
| bsr.c | ||
| ds1302.c | ||
| ds1620.c | ||
| dsp56k.c | ||
| dtlk.c | ||
| efirtc.c | ||
| generic_nvram.c | ||
| genrtc.c | ||
| hangcheck-timer.c | ||
| hpet.c | ||
| i8k.c | ||
| Kconfig | ||
| lp.c | ||
| Makefile | ||
| mbcs.c | ||
| mbcs.h | ||
| mem.c | ||
| misc.c | ||
| mmtimer.c | ||
| msm_smd_pkt.c | ||
| mspec.c | ||
| nsc_gpio.c | ||
| nvram.c | ||
| nwbutton.c | ||
| nwbutton.h | ||
| nwflash.c | ||
| pc8736x_gpio.c | ||
| ppdev.c | ||
| ps3flash.c | ||
| random.c | ||
| raw.c | ||
| rtc.c | ||
| scx200_gpio.c | ||
| snsc_event.c | ||
| snsc.c | ||
| snsc.h | ||
| sonypi.c | ||
| tb0219.c | ||
| tile-srom.c | ||
| tlclk.c | ||
| toshiba.c | ||
| ttyprintk.c | ||
| uv_mmtimer.c | ||
| virtio_console.c | ||