https://github.com/torvalds/linux
Revision d9ff0eb9ca4b00ce2fbf9ede1e99681f05c0bc91 authored by Youngmin Nam on 08 February 2016, 15:49:28 UTC, committed by Linus Walleij on 15 February 2016, 19:45:50 UTC
Previously, samsung_gpio_drection_in/output function were not covered
with a spinlock.
For example, samsung_gpio_direction_output function consists of
two functions.
1. samsung_gpio_set
2. samsung_gpio_set_direction
When 2 CPUs try to control the same gpio pin heavily,
(situation like i2c control with gpio emulation)
This situation can cause below problem.
CPU 0 | CPU1
|
samsung_gpio_direction_output |
samsung_gpio_set(pin A as 1) | samsung_gpio_direction_output
| samsung_gpio_set(pin A as 0)
samsung_gpio_set_direction |
| samsung_gpio_set_direction
The initial value of pin A will be set as 0 while we wanted to set pin A as 1.
This patch modifies samsung_gpio_direction_in/output function
to be done in one spinlock to fix race condition.
Additionally, the new samsung_gpio_set_value was added to implement
gpio set callback(samsung_gpio_set) with spinlock using this function.
Cc: stable@vger.kernel.org
Signed-off-by: Youngmin Nam <ym0914@gmail.com>
Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
1 parent 7864d92
Tip revision: d9ff0eb9ca4b00ce2fbf9ede1e99681f05c0bc91 authored by Youngmin Nam on 08 February 2016, 15:49:28 UTC
pinctrl: samsung: fix SMP race condition
pinctrl: samsung: fix SMP race condition
Tip revision: d9ff0eb
Kconfig.hz
#
# Timer Interrupt Frequency Configuration
#
choice
prompt "Timer frequency"
default HZ_250
help
Allows the configuration of the timer frequency. It is customary
to have the timer interrupt run at 1000 Hz but 100 Hz may be more
beneficial for servers and NUMA systems that do not need to have
a fast response for user interaction and that may experience bus
contention and cacheline bounces as a result of timer interrupts.
Note that the timer interrupt occurs on each processor in an SMP
environment leading to NR_CPUS * HZ number of timer interrupts
per second.
config HZ_100
bool "100 HZ"
help
100 Hz is a typical choice for servers, SMP and NUMA systems
with lots of processors that may show reduced performance if
too many timer interrupts are occurring.
config HZ_250
bool "250 HZ"
help
250 Hz is a good compromise choice allowing server performance
while also showing good interactive responsiveness even
on SMP and NUMA systems. If you are going to be using NTSC video
or multimedia, selected 300Hz instead.
config HZ_300
bool "300 HZ"
help
300 Hz is a good compromise choice allowing server performance
while also showing good interactive responsiveness even
on SMP and NUMA systems and exactly dividing by both PAL and
NTSC frame rates for video and multimedia work.
config HZ_1000
bool "1000 HZ"
help
1000 Hz is the preferred choice for desktop systems and other
systems requiring fast interactive responses to events.
endchoice
config HZ
int
default 100 if HZ_100
default 250 if HZ_250
default 300 if HZ_300
default 1000 if HZ_1000
config SCHED_HRTICK
def_bool HIGH_RES_TIMERS
Computing file changes ...
