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179fbd5a45
android_kernel_asus_sm8350/drivers
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David Vrabel 179fbd5a45 xen/evtchn: avoid a deadlock when unbinding an event channel 
Unbinding an event channel (either with the ioctl or when the evtchn
device is closed) may deadlock because disable_irq() is called with
port_user_lock held which is also locked by the interrupt handler.

Think of the IOCTL_EVTCHN_UNBIND is being serviced, the routine has
just taken the lock, and an interrupt happens. The evtchn_interrupt
is invoked, tries to take the lock and spins forever.

A quick glance at the code shows that the spinlock is a local IRQ
variant. Unfortunately that does not help as "disable_irq() waits for
the interrupt handler on all CPUs to stop running.  If the irq occurs
on another VCPU, it tries to take port_user_lock and can't because
the unbind ioctl is holding it." (from David). Hence we cannot
depend on the said spinlock to protect us. We could make it a system
wide IRQ disable spinlock but there is a better way.

We can piggyback on the fact that the existence of the spinlock is
to make get_port_user() checks be up-to-date. And we can alter those
checks to not depend on the spin lock (as it's protected by u->bind_mutex
in the ioctl) and can remove the unnecessary locking (this is
IOCTL_EVTCHN_UNBIND) path.

In the interrupt handler we cannot use the mutex, but we do not
need it.

"The unbind disables the irq before making the port user stale, so when
you clear it you are guaranteed that the interrupt handler that might
use that port cannot be running." (from David).

Hence this patch removes the spinlock usage on the teardown path
and piggybacks on disable_irq happening before we muck with the
get_port_user() data. This ensures that the interrupt handler will
never run on stale data.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v1: Expanded the commit description a bit]
2013-07-30 09:21:14 -04:00
..
accessibility
acpi ACPICA fixes for 3.10-rc1 2013-05-09 16:33:42 -07:00
amba
ata ARM: arm-soc: late cleanups 2013-05-07 11:22:14 -07:00
atm atm: he: use mdelay instead of large udelay constants 2013-04-29 13:26:48 -04:00
auxdisplay
base Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2013-05-01 13:20:04 -07:00
bcma - Lots of cleanups from Artem, including deletion of some obsolete drivers 2013-05-09 10:15:46 -07:00
block Merge git://git.infradead.org/users/willy/linux-nvme 2013-05-09 16:35:00 -07:00
bluetooth Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2013-05-01 14:08:52 -07:00
bus bus: mvebu: fix mistake in PCIe window target attribute for Kirkwood 2013-04-11 17:05:37 +00:00
cdrom block_device_operations->release() should return void 2013-05-07 02:16:21 -04:00
char aio: don't include aio.h in sched.h 2013-05-07 20:16:25 -07:00
clk ARM: late Exynos multiplatform changes 2013-05-07 11:28:42 -07:00
clocksource ARM: late Exynos multiplatform changes 2013-05-07 11:28:42 -07:00
connector
cpufreq Merge branch 'pm-cpufreq' 2013-04-29 00:08:46 +02:00
cpuidle cpuidle: add maintainer entry 2013-04-26 22:30:25 +02:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2013-05-02 14:53:12 -07:00
dca
devfreq
dio
dma Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma 2013-05-09 09:46:45 -07:00
edac Two small EDAC fixes. 2013-05-09 10:11:08 -07:00
eisa PCI changes for the v3.10 merge window: 2013-04-29 09:30:25 -07:00
extcon Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
firewire IEEE 1394 (FireWire) subsystem changes: 2013-05-09 10:11:48 -07:00
firmware Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
gpio Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
gpu Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2013-05-02 19:40:34 -07:00
hid HID: debug: fix RCU preemption issue 2013-05-06 13:07:33 +02:00
hsi
hv Merge branch 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:41:21 -07:00
hwmon Merge branch 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging 2013-05-04 13:44:38 -07:00
hwspinlock A single patch from Vincent extending OMAP's hwspinlock support to OMAP5. 2013-05-07 14:01:27 -07:00
i2c Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
ide block_device_operations->release() should return void 2013-05-07 02:16:21 -04:00
idle Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2013-05-11 15:23:17 -07:00
iio
infiniband InfiniBand/RDMA changes for the 3.10 merge window: 2013-05-08 15:29:48 -07:00
input Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
iommu IOMMU Updates for Linux v3.10 2013-05-06 14:59:13 -07:00
ipack
irqchip ARM: late Exynos multiplatform changes 2013-05-07 11:28:42 -07:00
isdn Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
leds Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
lguest Lots of virtio work which wasn't quite ready for last merge window. Plus 2013-05-02 14:14:04 -07:00
macintosh Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-05-02 10:16:16 -07:00
mailbox
md dm cache: set config value 2013-05-10 14:37:21 +01:00
media Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2013-05-02 14:38:53 -07:00
memory
memstick block_device_operations->release() should return void 2013-05-07 02:16:21 -04:00
message Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block 2013-05-08 10:13:35 -07:00
mfd For 3.10 we have a few new MFD drivers for: 2013-05-05 17:36:20 -07:00
misc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
mmc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-07 15:14:53 -07:00
mtd - Lots of cleanups from Artem, including deletion of some obsolete drivers 2013-05-09 10:15:46 -07:00
net Merge branch 'stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2013-05-09 14:34:58 -07:00
nfc NFC: pn544: Add MEI physical layer 2013-04-16 00:39:41 +02:00
ntb
nubus nubus: Kill nubus_proc_detach_device() 2013-05-04 14:47:26 -04:00
of net: of_mdio: fix behavior on missing phy device 2013-05-08 13:13:29 -07:00
oprofile
parisc parisc: fix partly 16/64k PAGE_SIZE boot 2013-05-06 23:08:32 +02:00
parport
pci xen/pcifront: Deal with toolstack missing 'XenbusStateClosing' state. 2013-06-14 12:28:59 -04:00
pcmcia
pinctrl Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
platform - Artem's removal of dead code continues (RPX, MBX860) 2013-05-10 09:09:47 -07:00
pnp Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-05-02 10:16:16 -07:00
power For 3.10 we have a few new MFD drivers for: 2013-05-05 17:36:20 -07:00
pps Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
ps3
ptp ptp: dynamic allocation of PHC char devices 2013-04-12 18:22:45 -04:00
pwm pwm: lpc32xx: Don't change PWM_ENABLE bit in lpc32xx_pwm_config 2013-04-23 10:58:47 +02:00
rapidio
regulator Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
remoteproc This pull request contains: 2013-05-07 14:04:56 -07:00
reset reset: NULL deref on allocation failure 2013-04-12 10:26:24 +02:00
rpmsg A small pull request consisting of: 2013-05-07 14:02:00 -07:00
rtc Merge branch 'stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2013-05-09 14:34:58 -07:00
s390 Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block 2013-05-08 10:13:35 -07:00
sbus
scsi Merge branch 'postmerge' into for-linus 2013-05-10 07:54:01 -07:00
sfi
sh
sn
spi Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
ssb - Lots of cleanups from Artem, including deletion of some obsolete drivers 2013-05-09 10:15:46 -07:00
ssbi
staging Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
target Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-05-01 17:51:54 -07:00
tc
thermal Merge branch 'cpu_cooling-doc-comments-update' of .git into next 2013-04-27 09:28:56 +08:00
tty Merge git://git.infradead.org/users/eparis/audit 2013-05-11 14:29:11 -07:00
uio
usb Merge branch 'stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile 2013-05-09 14:34:58 -07:00
uwb uwb: rename random32() to prandom_u32() 2013-04-29 18:28:43 -07:00
vfio vfio updates for v3.10 2013-05-02 14:02:32 -07:00
vhost vhost: more fixes for 3.10 2013-05-07 10:13:52 -07:00
video Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2013-05-10 07:48:05 -07:00
virt
virtio
vlynq
vme
w1 Removal of GENERIC_GPIO for v3.10 2013-05-09 09:59:16 -07:00
watchdog watchdog: Fix race condition in registration code 2013-05-09 08:13:41 +02:00
xen xen/evtchn: avoid a deadlock when unbinding an event channel 2013-07-30 09:21:14 -04:00
zorro proc: Supply PDE attribute setting accessor functions 2013-05-01 17:29:18 -04:00
Kconfig ARM: arm-soc driver changes for 3.10 2013-05-04 12:31:18 -07:00
Makefile ARM: arm-soc driver changes for 3.10 2013-05-04 12:31:18 -07:00