The device number in /dev may not be reliable from one boot to another
due to the initialization order of each bus.
For example, in Minnow Board Max, the exposed I2C buses may be i2c-7 and
i2c-8 or i2c-8 and i2c-9 depending if the platform driver in the kernel
is initialized before or after the PCI.
It also may change with different version and configuration of the DT or
UEFI used making another kernel driver to bind to the device. This means that
for Minnow Board Max we need to use something like below to pass to the
constructor:
static const char * const i2c_devpaths[] = {
/* UEFI with lpss set to ACPI */
"/devices/platform/80860F41:05",
/* UEFI with lpss set to PCI */
"/devices/pci0000:00/0000:00:18.6",
NULL
};
The devpath here is the one returned by udev with the following command:
udevadm info -q path /dev/<i2c-device>
In contrary to the device number in /dev/i2c-N, this path in sysfs is
stable across reboots and can only change if there's a change in the
UEFI firmware or the board's device tree.
This patch assumes the currently supported boards don't have this
problem so it's not touching them.
Instead of hardcoding 8 as the limit for I2C msgs, use whatever the
kernel exported to us. In upstream this is 42 so it means we can group
together 21 addr/data pair instead of only 8.
All threads share the same address space and have the same pages locked
into memory so it's not necessary to call mlockall() for each of them.
Grepping /proc/<tid>/status gives the same VmLck for all of them, even
when only the main thread locks the memory:
# for i in `seq 477 482`; do \
name=$(cat /proc/$i/comm); \
vm=$(cat /proc/$i/status |grep VmLck); \
echo -e "$name\t$vm"; \
done
ArduCopter.elf VmLck: 57868 kB
sched-timer VmLck: 57868 kB
sched-uart VmLck: 57868 kB
sched-rcin VmLck: 57868 kB
sched-tonealarm VmLck: 57868 kB
sched-io VmLck: 57868 kB
Use pthread_setname_np() to set thread name so it's easier to debug
what't going on with each of them. This is the example output of the
relevant par of "ps -Leo class,rtprio,wchan,comm":
FF 12 futex_ ArduCopter.elf
FF 15 usleep sched-timer
FF 14 hrtime sched-uart
FF 13 poll_s sched-rcin
FF 11 hrtime sched-tonealarm
FF 10 hrtime sched-io
It's undefined behavior to pass the callback to pthread to a class
member like we were doing. Refactor the code so the callbacks are static
members.
This fixes the following warnings:
libraries/AP_HAL_Linux/Scheduler.cpp: In member function 'virtual void Linux::LinuxScheduler::init(void*)':
/home/lucas/p/dronecode/ardupilot/libraries/AP_HAL_Linux/Scheduler.cpp:61:76: warning: converting from 'void* (Linux::LinuxScheduler::*)()' to 'Linux::LinuxScheduler::pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
(pthread_startroutine_t)&Linux::LinuxScheduler::_timer_thread);
^
libraries/AP_HAL_Linux/Scheduler.cpp:65:76: warning: converting from 'void* (Linux::LinuxScheduler::*)()' to 'Linux::LinuxScheduler::pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
(pthread_startroutine_t)&Linux::LinuxScheduler::_uart_thread);
^
libraries/AP_HAL_Linux/Scheduler.cpp:69:76: warning: converting from 'void* (Linux::LinuxScheduler::*)()' to 'Linux::LinuxScheduler::pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
(pthread_startroutine_t)&Linux::LinuxScheduler::_rcin_thread);
^
libraries/AP_HAL_Linux/Scheduler.cpp:73:76: warning: converting from 'void* (Linux::LinuxScheduler::*)()' to 'Linux::LinuxScheduler::pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
(pthread_startroutine_t)&Linux::LinuxScheduler::_tonealarm_thread);
^
libraries/AP_HAL_Linux/Scheduler.cpp:77:76: warning: converting from 'void* (Linux::LinuxScheduler::*)()' to 'Linux::LinuxScheduler::pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
(pthread_startroutine_t)&Linux::LinuxScheduler::_io_thread);
LinuxScheduler::init() was not really working as it should. This was the
result of "ps -Leo class,rtprio,wchan,comm | grep ArduCopter":
FF 12 futex_ ArduCopter.elf
FF 12 usleep ArduCopter.elf
FF 12 hrtime ArduCopter.elf
FF 12 poll_s ArduCopter.elf
FF 12 hrtime ArduCopter.elf
FF 12 hrtime ArduCopter.elf
As can be seen all the threads run with the same priority, the one of the main
thread. There were basically 2 mistakes:
1) pthread_attr_setschedpolicy() needs to be called before
pthread_attr_setschedparam(). Otherwise the latter will just return
an error and not set the priority
2) pthread_create() defaults to ignore the priority and inherit the
it from the parent thread. pthread_attr_setinheritsched() needs to
be called to change the behavior to PTHREAD_EXPLICIT_SCHED. See
pthread_attr_setinheritsched(3) for an example program to test the
behaviors.
Also, it's undefined behavior to call pthread_attr_init() several times on the
same pthread_attr_t. Although we could reutilize the same attribute without
calling pthread_attr_init() again, lets refactor the code a little bit, so all
the pthread calls are in a single place. Then also call pthread_attr_destroy()
when we are done.
In Linux the default stack size is always greater than 32k, either 2MB
or 8MB depending on the architecture. There's no point in creating a
function to lock 32k.
