linux/drivers/char
Peter Hurley e359a4e38d tty: Remove tty_hung_up_p() tests from tty drivers' open()
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>
2014-07-10 16:06:49 -07:00
..
agp agp: info leak in agpioc_info_wrap() 2014-05-06 13:05:00 -07:00
hw_random Main excitement is a virtio_scsi fix for alloc holding spinlock on the abort 2014-06-11 21:10:33 -07:00
ipmi Merge branch 'sched/urgent' into sched/core, to avoid conflicts 2014-05-07 13:15:46 +02:00
mwave drivers/char: delete non-required instances of include <linux/init.h> 2014-02-07 15:10:19 -08:00
pcmcia tty: Remove tty_hung_up_p() tests from tty drivers' open() 2014-07-10 16:06:49 -07:00
tpm Merge branch 'acpica' 2014-06-03 23:12:27 +02:00
xilinx_hwicap char: hwicap: Remove unnecessary dev_set_drvdata() 2013-10-03 16:03:31 -07:00
apm-emulation.c apm-emulation: add hibernation APM events to support suspend2disk 2014-01-07 13:50:28 +01:00
applicom.c applicom: dereferencing NULL on error path 2014-05-27 17:43:12 -07:00
applicom.h
bfin-otp.c
bsr.c drivers: clean-up prom.h implicit includes 2013-10-09 20:04:04 -05:00
ds1302.c
ds1620.c ds1620: single_open() leak 2013-05-05 00:11:29 -04:00
dsp56k.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
dtlk.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
efirtc.c rtc: single_open() leaks 2013-05-05 00:12:29 -04:00
generic_nvram.c
genrtc.c rtc: single_open() leaks 2013-05-05 00:12:29 -04:00
hangcheck-timer.c
hpet.c ACPI: Clean up inclusions of ACPI header files 2013-12-07 01:03:14 +01:00
i8k.c Merge branch 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging 2014-01-29 18:56:27 -08:00
Kconfig ttyprintk: Allow built as a module 2014-04-16 14:21:06 -07:00
lp.c char: Int overflow in lp_do_ioctl(). 2013-12-18 16:39:54 -08:00
Makefile Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2014-01-29 20:49:12 -08:00
mbcs.c char: remove use of __devinitconst 2012-11-21 12:55:19 -08:00
mbcs.h
mem.c /dev/mem: handle out-of-bounds read/write 2014-02-15 11:51:02 -08:00
misc.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-11-13 15:34:18 +09:00
mmtimer.c drivers/char/mmtimer.c: Remove useless kfree 2012-09-26 13:20:40 -07:00
msm_smd_pkt.c treewide: Fix typos in printk 2013-12-19 15:10:49 +01:00
mspec.c char: Use vma_pages() to replace (vm_end - vm_start) >> PAGE_SHIFT 2013-05-21 10:07:54 -07:00
nsc_gpio.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
nvram.c
nwbutton.c char: nwbutton: open-code interruptible_sleep_on 2014-01-08 15:29:52 -08:00
nwbutton.h
nwflash.c Merge branch 'late/fixes' into fixes 2012-10-07 07:22:32 -07:00
pc8736x_gpio.c pc8736x_gpio: use platform_device_unregister in pc8736x_gpio_cleanup() 2012-10-24 15:52:29 -07:00
ppdev.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
ps3flash.c ps3flash: switch to generic_file_llseek_size() 2013-06-29 12:57:33 +04:00
random.c random: fix entropy accounting bug introduced in v3.15 2014-06-17 14:23:14 -10:00
raw.c blkdev_aio_write() - turn into blkdev_write_iter() 2014-05-06 17:38:01 -04:00
rtc.c various char drivers: remove deprecated IRQF_DISABLED 2013-10-16 12:36:10 -07:00
scx200_gpio.c
snsc_event.c various char drivers: remove deprecated IRQF_DISABLED 2013-10-16 12:36:10 -07:00
snsc.c various char drivers: remove deprecated IRQF_DISABLED 2013-10-16 12:36:10 -07:00
snsc.h
sonypi.c ACPI: Remove the old /proc/acpi/event interface 2013-07-15 13:56:36 +02:00
tb0219.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
tile-srom.c drivers/char: delete non-required instances of include <linux/init.h> 2014-02-07 15:10:19 -08:00
tlclk.c tlclk: remove deprecated IRQF_DISABLED 2013-10-16 12:36:10 -07:00
toshiba.c
ttyprintk.c ttyprintk: Allow built as a module 2014-04-16 14:21:06 -07:00
uv_mmtimer.c
virtio_console.c pipe: kill ->map() and ->unmap() 2014-04-01 23:19:19 -04:00