nuttx/sched/Kconfig

#
# For a description of the syntax of this configuration file,
# see misc/tools/kconfig-language.txt.
#

menuconfig DISABLE_OS_API
	bool "Disable NuttX interfaces"
	default y
	---help---
		The following can be used to disable categories of
		APIs supported by the OS.  If the compiler supports
		weak functions, then it should not be necessary to
		disable functions unless you want to restrict usage
		of those APIs.

		There are certain dependency relationships in these
		features.

		1) mq_notify logic depends on signals to awaken tasks
		waiting for queues to become full or empty.
		2) pthread_condtimedwait() depends on signals to wake
		up waiting tasks.

if DISABLE_OS_API

config DISABLE_CLOCK
	bool "Disable clock interfaces"
	default n

config DISABLE_POSIX_TIMERS
	bool "Disable POSIX timers"
	default y if DEFAULT_SMALL
	default n if !DEFAULT_SMALL

config DISABLE_PTHREAD
	bool "Disable pthread support"
	default n

config DISABLE_SIGNALS
	bool "Disable signal support"
	default n

config DISABLE_MQUEUE
	bool "Disable POSIX message queue support"
	default n

config DISABLE_ENVIRON
	bool "Disable environment variable support"
	default y if DEFAULT_SMALL
	default n if !DEFAULT_SMALL

endif # DISABLE_OS_API

menu "Clocks and Timers"

config MSEC_PER_TICK
	int "Milliseconds per system timer tick"
	default 10
	---help---
		The default system timer is 100Hz or MSEC_PER_TICK=10.  This setting
		may be defined to inform NuttX that the processor hardware is providing
		system timer interrupts at some interrupt interval other than 10 msec.

config SYSTEM_TIME64
	bool "64-bit system clock"
	default n
	---help---
		The system timer is incremented at the rate determined by
		MSEC_PER_TICK, typically at 100Hz. The count at any given time is
		then the "uptime" in units of system timer ticks.  By default, the
		system time is 32-bits wide.  Those defaults provide a range of about
		13.6 years which is probably a sufficient range for "uptime".

		However, if the system timer rate is significantly higher than 100Hz
		and/or if a very long "uptime" is required, then this option can be
		selected to support a 64-bit wide timer.

config CLOCK_MONOTONIC
	bool "Support CLOCK_MONOTONIC"
	default n
	---help---
		CLOCK_MONOTONIC is an optional standard POSIX clock.  Unlike
		CLOCK_REALTIME which can move forward and backward when the
		time-of-day changes, CLOCK_MONOTONIC is the elapsed time since some
		arbitrary point in the post (the system start-up time for NuttX)
		and, hence, is always monotonically increasing.  CLOCK_MONOTONIC
		is, hence, the more appropriate clock for determining time
		differences.

		The value of the CLOCK_MONOTONIC clock cannot be set via clock_settime().

config JULIAN_TIME
	bool "Enables Julian time conversions"
	default n
	---help---
		Enables Julian time conversions

config START_YEAR
	int "Start year"
	default 2014

config START_MONTH
	int "Start month"
	default 1

config START_DAY
	int "Start day"
	default 1

config MAX_WDOGPARMS
	int "Maximum number of watchdog parameters"
	default 4
	---help---
		Maximum number of parameters that can be passed to a watchdog handler

config PREALLOC_WDOGS
	int "Number of pre-allocated watchdog timers"
	default 32
	---help---
		The number of pre-allocated watchdog structures.  The system manages a
		pool of preallocated watchdog structures to minimize dynamic allocations

config PREALLOC_TIMERS
	int "Number of pre-allocated POSIX timers"
	default 8
	---help---
		The number of pre-allocated POSIX timer structures.  The system manages a
		pool of preallocated timer structures to minimize dynamic allocations.  Set to
		zero for all dynamic allocations.

endmenu # Clocks and Timers

menu "Tasks and Scheduling"

config USER_ENTRYPOINT
	string "Application entry point"
	default "user_start"
	---help---
		The name of the entry point for user applications.  For the example
		applications this is of the form 'app_main' where 'app' is the application
		name. If not defined, USER_ENTRYPOINT defaults to "user_start."

config RR_INTERVAL
	int "Round robin timeslice (MSEC)"
	default 0
	---help---
		The round robin timeslice will be set this number of milliseconds;
		Round robin scheduling can be disabled by setting this value to zero.

config TASK_NAME_SIZE
	int "Maximum task name size"
	default 32
	---help---
		Spcifies that maximum size of a task name to save in the TCB.
		Useful if scheduler instrumentation is selected.  Set to zero to
		disable.

config MAX_TASK_ARGS
	int "Maximum number of task arguments"
	default 4
	---help---
		This controls the maximum number of of parameters that a task may
		receive (i.e., maxmum value of 'argc')

config MAX_TASKS
	int "Max number of tasks"
	default 32
	---help---
		The maximum number of simultaneously active tasks. This value must be
		a power of two.

config SCHED_HAVE_PARENT
	bool "Support parent/child task relationships"
	default n
	---help---
		Remember the ID of the parent task when a new child task is
		created.  This support enables some additional features (such as
		SIGCHLD) and modifies the behavior of other interfaces.  For
		example, it makes waitpid() more standards complete by restricting
		the waited-for tasks to the children of the caller. Default:
		disabled.

config SCHED_CHILD_STATUS
	bool "Retain child exit status"
	default n
	depends on SCHED_HAVE_PARENT
	---help---
		If this option is selected, then the exit status of the child task
		will be retained after the child task exits.  This option should be
		selected if you require knowledge of a child process' exit status.
		Without this setting, wait(), waitpid() or waitid() may fail.  For
		example, if you do:

		1) Start child task
		2) Wait for exit status (using wait(), waitpid(), or waitid()).

		This can fail because the child task may run to completion before
		the wait begins.  There is a non-standard work-around in this case:
		The above sequence will work if you disable pre-emption using
		sched_lock() prior to starting the child task, then re-enable pre-
		emption with sched_unlock() after the wait completes.  This works
		because the child task is not permitted to run until the wait is in
		place.

		The standard solution would be to enable SCHED_CHILD_STATUS.  In
		this case the exit status of the child task is retained after the
		child exits and the wait will successful obtain the child task's
		exit status whether it is called before the child task exits or not.

		Warning:  If you enable this feature, then your application must
		either (1) take responsibility for reaping the child status with wait(),
		waitpid(), or waitid(), or (2) suppress retention of child status.
		If you do not reap the child status, then you have a memory leak and
		your system will eventually fail.

		Retention of child status can be suppressed on the parent using logic like:

			struct sigaction sa;

			sa.sa_handler = SIG_IGN;
			sa.sa_flags = SA_NOCLDWAIT;
			int ret = sigaction(SIGCHLD, &sa, NULL);

if SCHED_CHILD_STATUS

config PREALLOC_CHILDSTATUS
	int "Number of pre-allocated child status"
	default 0
	---help---
		To prevent runaway child status allocations and to improve
		allocation performance, child task exit status structures are pre-
		allocated when the system boots.  This setting determines the number
		of child status structures that will be pre-allocated.  If this
		setting is not defined or if it is defined to be zero then a value
		of 2*MAX_TASKS is used.

		Note that there cannot be more that MAX_TASKS tasks in total.
		However, the number of child status structures may need to be
		significantly larger because this number includes the maximum number
		of tasks that are running PLUS the number of tasks that have exit'ed
		without having their exit status reaped (via wait(), waitid(), or
		waitpid()).

		Obviously, if tasks spawn children indefinitely and never have the
		exit status reaped, then you may have a memory leak!  If you enable
		the SCHED_CHILD_STATUS feature, then your application must take
		responsibility for either (1) reaping the child status with wait(),
		waitpid(), or waitid() or it must (2) suppress retention of child
		status.  Otherwise, your system will eventually fail.

		Retention of child status can be suppressed on the parent using logic like:

			struct sigaction sa;

			sa.sa_handler = SIG_IGN;
			sa.sa_flags = SA_NOCLDWAIT;
			int ret = sigaction(SIGCHLD, &sa, NULL);

config DEBUG_CHILDSTATUS
	bool "Enable Child Status Debug Output"
	default n
	depends on SCHED_CHILD_STATUS && DEBUG
	---help---
		Very detailed... I am sure that you do not want this.

endif # SCHED_CHILD_STATUS

config SCHED_WAITPID
	bool "Enable waitpid() API"
	default n
	---help---
		Enables the waitpid() interface in a default, non-standard mode
		(non-standard in the sense that the waited for PID need not be child
		of the caller).  If SCHED_HAVE_PARENT is also defined, then this
		setting will modify the behavior or waitpid() (making more spec
		compliant) and will enable the waitid() and wait() interfaces as
		well.

endmenu # Tasks and Scheduling

menu "Pthread Options"
	depends on !DISABLE_PTHREAD

config MUTEX_TYPES:
	bool "Enable mutex types"
	default n
	---help---
		Set to enable support for recursive and errorcheck mutexes. Enables
		pthread_mutexattr_settype().

config NPTHREAD_KEYS
	int "Maximum number of pthread keys"
	default 4
	---help---
		The number of items of thread-
		specific data that can be retained

endmenu # Pthread Options

menu "Performance Monitoring"

config SCHED_CPULOAD
	bool "Enable CPU load monitoring"
	default n
	---help---
		If this option is selected, the timer interrupt handler will monitor
		if the system is IDLE or busy at the time of that the timer interrupt
		occurs.  This is a very coarse measurement, but over a period of time,
		it can very accurately determined the percentage of the time that the
		CPU is IDLE.

		The statistics collected in this could be used, for example in the
		PROCFS file system to provide CPU load measurements when read.

if SCHED_CPULOAD

config SCHED_CPULOAD_EXTCLK
	bool "Use external clock"
	default n
	---help---
		The CPU load measurements are determined by sampling the active
		tasks periodically at the occurrence to a timer expiration.  By
		default, the system clock is used to do that sampling.

		There is a serious issue for the accuracy of measurements if the
		system clock is used, however.  NuttX threads are often started at
		the time of the system timer expiration.  Others may be stopped at
		the time of the system timer expiration (if round-robin time-slicing
		is enabled).  Such thread behavior occurs synchronously with the
		system timer and, hence, is not randomly sampled.  As a consequence,
		the CPU load attributed to these threads that run synchronously with
		they system timer may be grossly in error.

		The solution is to use some other clock that runs at a different
		rate and has timer expirations that are asynchronous with the
		system timer.  Then truly accurate load measurements can be
		achieved.  This option enables use of such an "external" clock.  The
		implementation of the clock must be provided by platform-specific
		logic; that platform-specific logic must call the system function
		sched_process_cpuload() at each timer expiration with interrupts
		disabled.

config SCHED_CPULOAD_TICKSPERSEC
	int "External clock rate"
	default 100
	depends on SCHED_CPULOAD_EXTCLK
	---help---
		If an external clock is used to drive the sampling for the CPU load
		calculations, then this value must be provided.  This value provides
		the rate of the external clock in units of ticks per second.  The
		default value of 100 corresponds to 100Hz clock.  NOTE: that 100Hz
		is the default frequency of the system time and, hence, the worst
		possible choice in most cases.

config SCHED_CPULOAD_TIMECONSTANT
	int "CPU load time constant"
	default 2
	---help---
		The accumulated CPU count is divided by two when the accumulated
		tick count exceeds this time constant.  This time constant is in
		units of seconds.

endif # SCHED_CPULOAD

config SCHED_INSTRUMENTATION
	bool "System performance monitor hooks"
	default n
	---help---
		Enables instrumentation in scheduler to monitor system performance.
		If enabled, then the board-specific logic must provide the following
		functions (see include/sched.h):

		void sched_note_start(FAR struct tcb_s *tcb);
		void sched_note_stop(FAR struct tcb_s *tcb);
		void sched_note_switch(FAR struct tcb_s *pFromTcb, FAR struct tcb_s *pToTcb);

endmenu # Performance Monitoring

menu "Files and I/O"

config DEV_CONSOLE
	bool "Enable /dev/console"
	default y
	---help---
		Set if architecture-specific logic provides /dev/console.  Enables
		stdout, stderr, stdin.

config FDCLONE_DISABLE
	bool "Disable cloning of file descriptors"
	default n
	---help---
	Disable cloning of all file descriptors
	by task_create() when a new task is started.  If set, all
	files/drivers will appear to be closed in the new task.

config FDCLONE_STDIO
	bool "Disable clone file descriptors without stdio"
	default n
	---help---
		Disable cloning of all but the first three file descriptors (stdin,
		stdout, stderr) by task_create() when a new task is started. If set,
		all files/drivers will appear to be closed in the new task except
		for stdin, stdout, and stderr.

config SDCLONE_DISABLE
	bool "Disable cloning of socket descriptors"
	default n
	---help---
	Disable cloning of all socket
	desciptors by task_create() when a new task is started. If
	set, all sockets will appear to be closed in the new task.

config NFILE_DESCRIPTORS
	int "Maximum number of file descriptors per task"
	default 16
	---help---
		The maximum number of file descriptors per task (one for each open)

config NFILE_STREAMS
	int "Maximum number of FILE streams"
	default 16
	---help---
		The maximum number of streams that can be fopen'ed

config NAME_MAX
	int "Maximum size of a file name"
	default 32
	---help---
	The maximum size of a file name.

endmenu # Files and I/O

menuconfig PRIORITY_INHERITANCE
	bool "Enable priority inheritance "
	default n
	---help---
		Set to enable support for priority inheritance on mutexes and semaphores.

if PRIORITY_INHERITANCE

config SEM_PREALLOCHOLDERS
	int "Number of pre-allocated holders"
	default 16
	---help---
		This setting is only used if priority inheritance is enabled.
		It defines the maximum number of different threads (minus one) that
		can take counts on a semaphore with priority inheritance support.
		This may be set to zero if priority inheritance is disabled OR if you
		are only using semaphores as mutexes (only one holder) OR if no more
		than two threads participate using a counting semaphore.

config SEM_NNESTPRIO
	int "Maximum number of higher priority threads"
	default 16
	---help---
		If priority inheritance is enabled, then this setting is the
		maximum number of higher priority threads (minus 1) than can be
		waiting for another thread to release a count on a semaphore.
		This value may be set to zero if no more than one thread is
		expected to wait for a semaphore.

endif # PRIORITY_INHERITANCE

menu "RTOS hooks"

config BOARD_INITIALIZE
	bool "Custom board/driver initialization"
	default n
	---help---
		By default, there are three points in time where you can insert
		custom initialization logic:

		1) <arch>_boardinitialize():  This function is used only for
		initialization of very low-level things like configuration of
		GPIO pins, power setting.  The OS has not been initialized
		at this point, so you cannot allocate memory or initialize
		device drivers at this phase.

		2) The next level of initialization is performed by a call to
		up_initialize() (in arch/<arch>/src/common/up_initialize.c).
		The OS has been initialized at this point and it is okay to
		initialize drivers in this phase.

		3) And, finally, when the user application code starts.

		If BOARD_INITIALIZE is selected, then an additional initialization
		call will be performed in the boot-up sequence to a function
		called board_initialize().  board_initialize() will be
		call between phases 2) and 3) above, immediately after
		up_initialize() is called.  This additional initialization
		phase may be used, for example, to initialize board-specific
		device drivers.

config SCHED_STARTHOOK
	bool "Enable startup hook"
	default n
	---help---
		Enable a non-standard, internal OS API call task_starthook().
		task_starthook() registers a function that will be called on task
		startup before that actual task entry point is called.  The
		starthook is useful, for example, for setting up automatic
		configuration of C++ constructors.

config SCHED_ATEXIT
	bool "Enable atexit() API"
	default n
	---help---
		Enables the atexit() API

config SCHED_ATEXIT_MAX
	int "Max number of atexit() functions"
	default 1
	depends on SCHED_ATEXIT && !SCHED_ONEXIT
	---help---
		By default if SCHED_ATEXIT is selected, only a single atexit() function
		is supported. That number can be increased by defined this setting to
		the number that you require.

		If both SCHED_ONEXIT and SCHED_ATEXIT are selected, then atexit() is built
		on top of the on_exit() implementation.  In that case, SCHED_ONEXIT_MAX
		determines the size of the combined number of atexit(0) and on_exit calls
		and SCHED_ATEXIT_MAX is not used.

config SCHED_ONEXIT
	bool "Enable on_exit() API"
	default n
	---help---
		Enables the on_exit() API

config SCHED_ONEXIT_MAX
	int "Max number of on_exit() functions"
	default 1
	depends on SCHED_ONEXIT
	---help---
		By default if SCHED_ONEXIT is selected, only a single on_exit() function
		is supported. That number can be increased by defined this setting to the
		number that you require.

		If both SCHED_ONEXIT and SCHED_ATEXIT are selected, then atexit() is built
		on top of the on_exit() implementation.  In that case, SCHED_ONEXIT_MAX
		determines the size of the combined number of atexit(0) and on_exit calls.

endmenu # RTOS hooks

menu "Signal Numbers"
	depends on !DISABLE_SIGNALS

config SIG_SIGUSR1
	int "SIGUSR1"
	default 1
	---help---
		Value of standard user signal 1 (SIGUSR1). Default: 1

config SIG_SIGUSR2
	int "SIGUSR2"
	default 2
	---help---
		Value of standard user signal 2 (SIGUSR2). Default: 2

config SIG_SIGALARM
	int "SIGALRM"
	default 3
	---help---
		Default the signal number used with POSIX timers (SIGALRM).
		Default: 3

config SIG_SIGCHLD
	int "SIGCHLD"
	default 4
	depends on SCHED_HAVE_PARENT
	---help---
		The SIGCHLD signal is sent to the parent of a child process when it
		exits, is interrupted (stopped), or resumes after being interrupted.
		Default: 4

config SIG_SIGCONDTIMEDOUT
	int "SIGCONDTIMEDOUT"
	default 16
	depends on !DISABLE_PTHREAD
	---help---
		This non-standard signal number is used the implementation of
		pthread_cond_timedwait(). Default 16.

config SIG_SIGWORK
	int "SIGWORK"
	default 17
	depends on SCHED_WORKQUEUE
	---help---
		SIGWORK is a non-standard signal used to wake up the internal NuttX
		worker thread.  This setting specifies the signal number that will be
		used for SIGWORK.  Default: 17

endmenu # Signal Numbers

menu "POSIX Message Queue Options"
	depends on !DISABLE_MQUEUE

config PREALLOC_MQ_MSGS
	int "Number of pre-allocated messages"
	default 32
	---help---
		The number of pre-allocated message structures.  The system manages
		a pool of preallocated message structures to minimize dynamic allocations

config MQ_MAXMSGSIZE
	int "Maximum message size"
	default 32
	---help---
		Message structures are allocated with a fixed payload size given by this
		setting (does not include other message structure overhead.

endmenu # POSIX Message Queue Options

menu "Stack and heap information"

config IDLETHREAD_STACKSIZE
	int "Idle thread stack size"
	default 1024
	---help---
		The size of the initial stack used by the IDLE thread.  The IDLE thread
		is the thread that (1) performs the inital boot of the system up to the
		point where user_start() is spawned, and (2) there after is the IDLE
		thread that executes only when there is no other thread ready to run.

config USERMAIN_STACKSIZE
	int "Main thread stack size"
	default 2048
	---help---
		The size of the stack to allocate for the main user thread that begins at
		the user_start() entry point.

config PTHREAD_STACK_MIN
	int "Minimum pthread stack size"
	default 256
	---help---
		Minimum pthread stack size

config PTHREAD_STACK_DEFAULT
	int "Default pthread stack size"
	default 2048
	---help---
		Default pthread stack size

endmenu # Stack and heap information