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Linus Torvalds 0b5759c654 tty: Avoid dropping ldisc_mutex over hangup tty re-initialization 
A couple of people have hit the WARN_ON() in drivers/char/tty_io.c,
tty_open() that is unhappy about seeing the tty line discipline go away
during the tty hangup. See for example

	http://bugzilla.kernel.org/show_bug.cgi?id=14255

and the reason is that we do the tty_ldisc_halt() outside the
ldisc_mutex in order to be able to flush the scheduled work without a
deadlock with vhangup_work.

However, it turns out that we can solve this particular case by

 - using "cancel_delayed_work_sync()" in tty_ldisc_halt(), which waits
   for just the particular work, rather than synchronizing with any
   random outstanding pending work.

   This won't deadlock, since the buf.work we synchronize with doesn't
   care about the ldisc_mutex, it just flushes the tty ldisc buffers.

 - realize that for this particular case, we don't need to wait for any
   hangup work, because we are inside the hangup codepaths ourselves.

so as a result we can just drop the flush_scheduled_work() entirely, and
then move the tty_ldisc_halt() call to inside the mutex.  That way we
never expose the partially torn down ldisc state to tty_open(), and hold
the ldisc_mutex over the whole sequence.

Reported-by: Ingo Molnar <mingo@elte.hu>
Reported-by: Heinz Diehl <htd@fancy-poultry.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-03 21:44:21 -07:00
..
accessibility
acpi const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
amba
ata trivial: fix comment typo in drivers/ata/pata_hpt37x.c 2009-09-21 15:15:53 +02:00
atm net: Make setsockopt() optlen be unsigned. 2009-09-30 16:12:20 -07:00
auxdisplay
base mm: oom analysis: add shmem vmstat 2009-09-22 07:17:27 -07:00
block const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
bluetooth
cdrom sysctl: remove "struct file *" argument of ->proc_handler 2009-09-24 07:21:04 -07:00
char tty: Avoid dropping ldisc_mutex over hangup tty re-initialization 2009-10-03 21:44:21 -07:00
clocksource
connector connector: Removed the destruct_data callback since it is always kfree_skb() 2009-10-02 10:54:05 -07:00
cpufreq Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq 2009-09-18 09:16:57 -07:00
cpuidle cpuidle: menu governor: reduce latency on exit 2009-09-22 07:17:45 -07:00
crypto
dca
dio
dma Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx into for-linus 2009-09-23 18:31:11 +10:00
edac edac: core: remove completion-wait for complete with rcu_barrier 2009-09-24 07:21:05 -07:00
eisa
firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2009-09-23 09:43:22 -07:00
firmware mm: don't use alloc_bootmem_low() where not strictly needed 2009-09-22 07:17:38 -07:00
gpio const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
gpu Merge branch 'drm-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6 2009-09-30 08:03:00 -07:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid 2009-09-22 07:51:28 -07:00
hwmon const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
i2c ACPI: i2c-scmi: don't use acpi_device_uid() 2009-09-26 01:42:07 -04:00
ide Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 2009-09-23 09:32:11 -07:00
idle
ieee1394 const: mark struct vm_struct_operations 2009-09-27 11:39:25 -07:00
ieee802154
infiniband const: mark struct vm_struct_operations 2009-09-27 11:39:25 -07:00
input drivers/input/input.c: fix CONFIG_PM=n warning 2009-10-01 16:11:11 -07:00
isdn net: Make setsockopt() optlen be unsigned. 2009-09-30 16:12:20 -07:00
leds Merge branch 'for-linus' of git://git.o-hand.com/linux-rpurdie-leds 2009-09-26 10:50:47 -07:00
lguest const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
macintosh Merge branch 'for-linus' of git://git.o-hand.com/linux-rpurdie-leds 2009-09-26 10:50:47 -07:00
mca
md dm/connector: Only process connector packages from privileged processes 2009-10-02 10:54:10 -07:00
media const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
memstick memstick: move dev_dbg 2009-09-24 07:21:05 -07:00
message Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2009-09-22 07:51:45 -07:00
mfd mfd/gpio: add a GPIO interface to the UCB1400 MFD chip driver via gpiolib 2009-09-23 07:39:48 -07:00
misc const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
mmc Merge master.kernel.org:/home/rmk/linux-2.6-arm 2009-10-02 16:20:43 -07:00
mtd Merge branch 'for-linus' of git://git.monstr.eu/linux-2.6-microblaze 2009-09-24 09:01:44 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2009-10-02 13:37:18 -07:00
nubus
of of: remove "stm,m25p40" alias 2009-09-23 07:39:43 -07:00
oprofile cpumask: use zalloc_cpumask_var() where possible 2009-09-24 09:34:24 +09:30
parisc mm: replace various uses of num_physpages by totalram_pages 2009-09-22 07:17:38 -07:00
parport sysctl: remove "struct file *" argument of ->proc_handler 2009-09-24 07:21:04 -07:00
pci ACPICA: fixup after acpi_get_object_info() change 2009-09-25 14:24:22 -04:00
pcmcia Merge master.kernel.org:/home/rmk/linux-2.6-arm 2009-10-02 16:20:43 -07:00
platform Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2009-09-30 08:07:12 -07:00
pnp ACPI: remove acpi_device.flags.hardware_id 2009-09-25 15:09:48 -04:00
power Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 2009-09-23 03:49:27 +04:00
pps
ps3
rapidio
regulator regulator: fix voltage range in da9034 ldo12 2009-09-22 13:58:23 +01:00
rtc Merge branch 'origin' into for-linus 2009-09-24 21:22:33 +01:00
s390 const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
sbus const: make block_device_operations const 2009-09-22 07:17:25 -07:00
scsi const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
serial Merge master.kernel.org:/home/rmk/linux-2.6-arm 2009-10-02 16:20:43 -07:00
sfi
sh
sn
spi spi-imx: strip down chipselect function to only drive the chipselect 2009-10-01 16:11:17 -07:00
ssb ssb/sdio: fix printk format warnings 2009-09-23 11:35:41 -04:00
staging pohmelfs/connector: Disallow unpliviged users to configure pohmelfs 2009-10-02 10:54:15 -07:00
tc
telephony
thermal thermal: add missing Kconfig dependency 2009-09-19 01:41:49 -04:00
uio const: mark struct vm_struct_operations 2009-09-27 11:39:25 -07:00
usb const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
uwb const: constify remaining file_operations 2009-10-01 16:11:11 -07:00
video Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2009-10-02 13:37:18 -07:00
virtio virtio: add virtio IDs file 2009-09-23 22:26:32 +09:30
vlynq drivers/vlynq/vlynq.c: fix resource size off by 1 error 2009-09-24 07:21:05 -07:00
w1 connector: Provide the sender's credentials to the callback 2009-10-02 10:54:01 -07:00
watchdog [WATCHDOG] Add support for the Avionic Design Xanthos watchdog timer. 2009-09-25 08:38:16 +00:00
xen Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2009-09-22 07:51:45 -07:00
zorro
Kconfig
Makefile Merge git://git.infradead.org/mtd-2.6 2009-09-23 10:07:49 -07:00