nuttx/sched/Kconfig

#
# For a description of the syntax of this configuration file,
# see the file kconfig-language.txt in the NuttX tools repository.
#

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_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 ARCH_HAVE_TICKLESS
	bool

config SCHED_TICKLESS
	bool "Support tick-less OS"
	default n
	depends on ARCH_HAVE_TICKLESS
	---help---
		By default, system time is driven by a periodic timer interrupt.  An
		alternative configurations is a tick-less configuration in which
		there is no periodic timer interrupt.  Instead and interval timer is
		used to schedule the next OS time event.  This option selects that
		tick-less OS option.  If the tick-less OS is selected, then there are
		additional platform specific interfaces that must be provided as
		defined include/nuttx/arch.h

if SCHED_TICKLESS

config SCHED_TICKLESS_ALARM
	bool "Tickless alarm"
	default n
	---help---
		The tickless option can be supported either via a simple interval
		timer (plus elapsed time) or via an alarm.  The interval timer allows
		programming events to occur after an interval.  With the alarm,
		you can set a time in the future and get an event when that alarm
		goes off.  This option selects the use of an alarm.

		The advantage of an alarm is that it avoids some small timing
		errors; the advantage of the use of the interval timer is that
		the hardware requirement may be less.

config SCHED_TICKLESS_LIMIT_MAX_SLEEP
	bool "Max sleep period (in microseconds)"
	default n
	---help---
		Enables use of the g_oneshot_maxticks variable. This variable is
		initialized by platform-specific logic at runtime to the maximum
		delay that the timer can wait (in configured clock ticks).  The
		RTOS tickless logic will then limit all requested delays to this
		value.

endif

config USEC_PER_TICK
	int "System timer tick period (microseconds)"
	default 10000 if !SCHED_TICKLESS
	default 100 if SCHED_TICKLESS
	---help---
		In the "normal" configuration where system time is provided by a
		periodic timer interrupt, the default system timer is expected to
		run at 100Hz or USEC_PER_TICK=10000.  This setting must be defined
		to inform of NuttX the interval that the the processor hardware is
		providing system timer interrupts to the OS.

		If SCHED_TICKLESS is selected, then there are no system timer
		interrupts.  In this case, USEC_PER_TICK does not control any timer
		rates.  Rather, it only determines the resolution of time reported
		by clock_systimer() and the resolution of times that can be set for
		certain delays including watchdog timers and delayed work.  In this
		case there is a trade-off:  It is better to have the USEC_PER_TICK as
		low as possible for higher timing resolution.  However, the the time
		is currently held in 'unsigned int' on some systems, this may be
		16-bits but on most contemporary systems it will be 32-bits.  In
		either case, smaller values of USEC_PER_TICK will reduce the range
		of values that delays that can be represented.  So the trade-off is
		between range and resolution (you could also modify the code to use
		a 64-bit value if you really want both).

		The default, 100 microseconds, will provide for a range of delays
		up to 120 hours.

		This value should never be less than the underlying resolution of
		the timer.  Error may ensue.

if !SCHED_TICKLESS

config SYSTEMTICK_EXTCLK
	bool "Use external clock"
	default n
	depends on ARCH_HAVE_EXTCLK
	---help---
		Use external clock for system tick. When enabled, the platform-specific
		logic must start its own timer interrupt to make periodic calls to the
		sched_process_timer() or the functions called within. The purpose is
		to move the scheduling off the processor clock to allow entering low
		power states that would disable that clock.

endif # !SCHED_TICKLESS

config SYSTEM_TIME64
	bool "64-bit system clock"
	default n
	---help---
		The system timer is incremented at the rate determined by
		USEC_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
		497 days 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 ARCH_HAVE_TIMEKEEPING
	bool
	default n

config CLOCK_TIMEKEEPING
	bool "Support timekeeping algorithms"
	default n
	depends on EXPERIMENTAL && ARCH_HAVE_TIMEKEEPING
	---help---
		CLOCK_TIMEKEEPING enables experimental time management algorithms.

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

config START_YEAR
	int "Start year"
	default 2017
	range 1970 2106
	---help---
		NuttX uses an unsigned 32-bit integer for time_t which provides a
		range from 1970 to 2106.

config START_MONTH
	int "Start month"
	default 1
	range 1 12

config START_DAY
	int "Start day"
	default 1
	range 1 31

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.  Dynamic allocations will still be made if this pool is
		exhausted.  You will, however, get better performance and memory
		usage if this value is tuned to minimize such allocations.

config WDOG_INTRESERVE
	int "Watchdog structures reserved for interrupt handlers"
	default 4
	---help---
		Watchdog structures may be allocated from normal task and also from
		interrupt handlers.  Interrupt handlers, however, can only use pre-
		allocated watchdog timer.  So, in order to keep normal task
		allocations from exhausting all watchdog structures, a small number
		of pre-allocated watchdog timers must be reserved for exclusive use
		by interrupt handler.  This setting determines that number of
		reserved watchdogs.

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 SPINLOCK
	bool "Support Spinlocks"
	default n
	---help---
		Enables suppport for spinlocks.  Spinlocks are current used only for
		SMP suppport.

config SMP
	bool "Symmetric Multi-Processing (SMP)"
	default n
	depends on ARCH_HAVE_MULTICPU
	select SPINLOCK
	---help---
		Enables support for Symmetric Multi-Processing (SMP) on a multi-CPU
		platform.

if SMP

config SMP_NCPUS
	int "Number of CPUs"
	default 4
	range 1 32 if DEBUG_FEATURES
	range 2 32 if !DEBUG_FEATURES
	---help---
		This value identifies the number of CPUs supported by the processor
		that will be used for SMP.

		If CONFIG_DEBUG_FEATURES is enbled, then the value one is permitted
		for CONFIG_SMP_NCPUS.  This is not normally a valid setting for an
		SMP configuration.  However, running the SMP logic in a single CPU
		configuration is useful during certain testing.

config SMP_IDLETHREAD_STACKSIZE
	int "CPU IDLE stack size"
	default 2048
	---help---
		Each CPU will have its own IDLE task.  System initialization occurs
		on CPU0 and uses CONFIG_IDLETHREAD_STACKSIZE which will probably be
		larger than is generally needed.  This setting provides the stack
		size for the IDLE task on CPUS 1 through (CONFIG_SMP_NCPUS-1).

endif # SMP

choice
	prompt "Initialization Task"
	default INIT_ENTRYPOINT if !BUILD_KERNEL
	default INIT_FILEPATH if BUILD_KERNEL && !BINFMT_DISABLE
	default INIT_NONE if BUILD_KERNEL && BINFMT_DISABLE

config INIT_NONE
	bool "None"

config INIT_ENTRYPOINT
	bool "Via application entry point"
	depends on !BUILD_KERNEL

config INIT_FILEPATH
	bool "Via executable file"
	depends on !BINFMT_DISABLE

endchoice # Initialization task

if INIT_ENTRYPOINT
config USER_ENTRYPOINT
	string "Application entry point"
	default "main"
	---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 "main".

endif # INIT_ENTRYPOINT

if INIT_FILEPATH

config USER_INITPATH
	string "Application initialization path"
	default "/bin/init"
	---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 "main".

config INIT_SYMTAB
	string "Symbol table"
	default "NULL"
	depends on !BUILD_PROTECTED && !BUILD_KERNEL
	---help---
		The name of othe global array that holds the exported symbol table.
		The special string "NULL" may be provided if there is no symbol
		table.  Quotation marks will be stripped when config.h is generated.

		NOTE: This setting cannot be used in protected or kernel builds.
		Any kernel mode symbols tables would not be usable for resolving
		symbols in user mode executables.

config INIT_NEXPORTS
	string "Symbol table size"
	default "0"
	depends on !BUILD_PROTECTED && !BUILD_KERNEL
	---help---
		The size of the symbol table.  NOTE that is is logically a numeric
		value but is represent by a string.  That allows you to put
		sizeof(something) or a macro or a global variable name for the
		symbol table size.  Quotation marks will be stripped when config.h
		is generated.

		NOTE: This setting cannot be used in protected or kernel builds.
		Any kernel mode symbols tables would not be usable for resolving
		symbols in user mode executables.

endif # INIT_FILEPATH

config RR_INTERVAL
	int "Round robin timeslice (MSEC)"
	default 0
	---help---
		The round robin timeslice will be set this number of milliseconds;
		Round roben scheduling (SCHED_RR) is enabled by setting this
		interval to a positive, non-zero value.

config SCHED_SPORADIC
	bool "Support sporadic scheduling"
	default n
	---help---
		Build in additional logic to support sporadic scheduling
		(SCHED_SPORADIC).

if SCHED_SPORADIC

config SCHED_SPORADIC_MAXREPL
	int "Maximum number of replenishments"
	default 3
	range 1 255
	---help---
		Controls the size of allocated replenishment structures and, hence,
		also limits the maximum number of replenishments.

config SPORADIC_INSTRUMENTATION
	bool "Sporadic scheduler monitor hooks"
	default n
	---help---
		Enables instrumentation in the sporadic scheduler to monitor
		scheduler behavior. If enabled, then the board-specific logic must
		provide the following functions:

			void arch_sporadic_start(FAR struct tcb_s *tcb);
			void arch_sporadic_lowpriority(FAR struct tcb_s *tcb);
			void arch_sporadic_suspend(FAR struct tcb_s *tcb);
			void arch_sporadic_resume(FAR struct tcb_s *tcb);

endif # SCHED_SPORADIC

config TASK_NAME_SIZE
	int "Maximum task name size"
	default 31
	---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.  Excludes the NUL terminator; the actual allocated size
		willl be TASK_NAME_SIZE + 1.  The default of 31 then results in
		a align-able 32-byte allocation.::

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 than 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_FEATURES
	---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 PTHREAD_MUTEX_TYPES
	bool "Enable mutex types"
	default n
	---help---
		Set to enable support for recursive and errorcheck mutexes. Enables
		pthread_mutexattr_settype().

choice
	prompt "pthread mutex robustness"
	default PTHREAD_MUTEX_ROBUST if !DEFAULT_SMALL
	default PTHREAD_UNSAFE if DEFAULT_SMALL

config PTHREAD_MUTEX_ROBUST
	bool "Robust mutexes"
	---help---
		Support only the robust form of the NORMAL mutex.

config PTHREAD_MUTEX_UNSAFE
	bool "Traditional unsafe mutexes"
	---help---
		Support only the traditional non-robust form of the NORMAL mutex.
		You should select this option only for backward compatibility with
		software you may be porting or, perhaps, if you are trying to minimize
		footprint.

config PTHREAD_MUTEX_BOTH
	bool "Both robust and unsafe mutexes"
	---help---
		Support both forms of NORMAL mutexes.

endchoice # pthread mutex robustness

choice
	prompt "Default NORMAL mutex robustness"
	default PTHREAD_MUTEX_DEFAULT_ROBUST
	depends on PTHREAD_MUTEX_BOTH

config PTHREAD_MUTEX_DEFAULT_ROBUST
	bool "Robust default"
	---help---
		The default is robust NORMAL mutexes (non-standard)

config PTHREAD_MUTEX_DEFAULT_UNSAFE
	bool "Unsafe default"
	---help---
		The default is traditional unsafe NORMAL mutexes (standard)

endchoice # Default NORMAL mutex robustness

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

config PTHREAD_CLEANUP
	bool "pthread cleanup stack"
	default n
	---help---
		Select to enable support for pthread exit cleanup stacks.  This
		enables the interfaces pthread_cleanup_push() and
		pthread_cleanup_pop().

config PTHREAD_CLEANUP_STACKSIZE
	int "pthread cleanup stack size"
	default 1
	range 1 32
	depends on PTHREAD_CLEANUP
	---help---
		The maximum number of cleanup actions that may be pushed by
		pthread_clean_push().  This setting will increase the size of EVERY
		pthread task control block by about n * CONFIG_PTHREAD_CLEANUP_STACKSIZE
		where n is the size of a pointer, 2* sizeof(uintptr_t), this would be
		8 for a CPU with 32-bit addressing and 4 for a CPU with 16-bit
		addressing.

endmenu # Pthread Options

config CANCELLATION_POINTS
	bool "Cancellation points"
	default n
	---help---
		Enable POSIX cancellation points for pthread_cancel().  If selected,
		cancellation points will also used with the () task_delete() API even if
		pthreads are not enabled.

menu "Performance Monitoring"

config SCHED_CPULOAD
	bool "Enable CPU load monitoring"
	default n
	select SCHED_CPULOAD_EXTCLK if SCHED_TICKLESS
	---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.

		Note that in tickless mode of operation (SCHED_TICKLESS) there is
		no system timer interrupt and CPU load measurements will not be
		possible unless you provide an alternative clock to driver the
		sampling and select SCHED_CPULOAD_EXTCLK.

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.

if SCHED_CPULOAD_EXTCLK

config SCHED_CPULOAD_TICKSPERSEC
	int "External clock rate"
	default 100
	---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 interrupts in units of ticks per
		second.  The default value of 100 corresponds to a 100Hz clock.  NOTE:
		that 100Hz is the default frequency of the system time and, hence,
		the worst possible choice in most cases.

config CPULOAD_ONESHOT
	bool "Use Oneshot timer"
	default n
	---help---
		Use an MCU-specific oneshot timer as the external clock.  The
		oneshot timer must be configured by board specific logic which must
		then call:

			void sched_oneshot_extclk(FAR struct oneshot_lowerhalf_s *lower);

		To start the CPU load measurement. See include/nuttx/clock.h

		NOTE that in this configuration, CONFIG_SCHED_CPULOAD_TICKSPERSEC is
		the sample rate that will be accomplished by programming the oneshot
		time repeatedly.  If CPULOAD_ONESHOT_ENTROPY is also selected, then
		the underly frequency driving the oneshote timer must be
		significantly faster than CONFIG_SCHED_CPULOAD_TICKSPERSE to permit
		precise modulation the sample periods.

config CPULOAD_ONESHOT_ENTROPY
	int "Bits of entropy"
	default 6
	range 0 30
	---help---
		This is the number of bits of entropy that will be applied. The
		oneshot will be set to this interval:

			CPULOAD_ONESHOT_NOMINAL - (CPULOAD_ONESHOT_ENTROPY / 2) +
			error + nrand(CPULOAD_ONESHOT_ENTROPY)

		Where

			CPULOAD_ONESHOT_NOMINAL is the nominal sample internval implied
			by CONFIG_SCHED_CPULOAD_TICKSPERSEC in units of microseconds.
			CPULOAD_ONESHOT_ENTROPY is (1 << CONFIG_CPULOAD_ONESHOT_ENTROPY),
			and
			'error' is an error value that is retained from interval to
			interval so that although individual intervals are randomized,
			the average will still be CONFIG_SCHED_CPULOAD_TICKSPERSEC.

		This special value of zero disables entropy.

endif # SCHED_CPULOAD_EXTCLK

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_suspend(FAR struct tcb_s *tcb);
			void sched_note_resume(FAR struct tcb_s *tcb);

		If CONFIG_SMP is enabled, then these additional interfaces are
		expected:

			void sched_note_cpu_pause(FAR struct tcb_s *tcb, int cpu);
			void sched_note_cpu_paused(FAR struct tcb_s *tcb);
			void sched_note_cpu_resume(FAR struct tcb_s *tcb, int cpu);
			void sched_note_cpu_resumed(FAR struct tcb_s *tcb);

		NOTE: These are internal OS interfaces and are called at at very
		critical locations in the OS. There is very little that can be
		done in these interfaces.  For example, normal devices may not be
		used; syslog output cannot be performed.

		An option is to use SCHED_INSTRUMENTATION_BUFFER below.

if SCHED_INSTRUMENTATION

config SCHED_INSTRUMENTATION_CPUSET
	hex "CPU bit set"
	default 0xffff
	depends on SMP
	---help---
		Monitor only CPUs in the bitset.  Bit 0=CPU0, Bit1=CPU1, etc.

config SCHED_INSTRUMENTATION_PREEMPTION
	bool "Preemption monitor hooks"
	default n
	---help---
		Enables additional hooks for changes to pre-emption state.  Board-
		specific logic must provide this additional logic.

			void sched_note_premption(FAR struct tcb_s *tcb, bool state);

config SCHED_INSTRUMENTATION_CSECTION
	bool "Critical section monitor hooks"
	default n
	---help---
		Enables additional hooks for entry and exit from critical sections.
		Interrupts are disabled while within a critical section.  Board-
		specific logic must provide this additional logic.

			void sched_note_csection(FAR struct tcb_s *tcb, bool state);

config SCHED_INSTRUMENTATION_SPINLOCKS
	bool "Spinlock monitor hooks"
	default n
	---help---
		Enables additional hooks for spinlock state.  Board-specific logic
		must provide this additional logic.

			void sched_note_spinlock(FAR struct tcb_s *tcb, bool state);
			void sched_note_spinlocked(FAR struct tcb_s *tcb, bool state);
			void sched_note_spinunlock(FAR struct tcb_s *tcb, bool state);
			void sched_note_spinabort(FAR struct tcb_s *tcb, bool state);

config SCHED_INSTRUMENTATION_BUFFER
	bool "Buffer instrumentation data in memory"
	default n
	---help---
		If this option is selected, then in-memory buffering logic is
		enabled to capature scheduler instrumentation data.  This has
		the advantage that (1) the platform logic does not have to provide
		the sched_note_* interaces described for the previous settings.
		Instead, the buffering logic catches all of these.  It encodes
		timestamps the scheduler note and adds the note to an in-memory,
		circular buffer.  And (2) buffering the scheduler instrumentation
		data (versus performing some output operation) minimizes the impact
		of the instrumentation on the behavior of the system.

		If the in-memory buffer becomes full, then older notes are
		overwritten by newer notes.  The following interface is provided:

			ssize_t sched_note_get(FAR uint8_t *buffer, size_t buflen);

		Platform specific information must call this function and dispose
		of it quickly so that overwriting of the tail of the circular buffer
		does not occur.  See include/nuttx/sched_note.h for additional
		information.

if SCHED_INSTRUMENTATION_BUFFER

config SCHED_NOTE_BUFSIZE
	int "Instrumentation buffer size"
	default 2048
	---help---
		The size of the in-memory, circular instrumentation buffer (in
		bytes).

config SCHED_NOTE_GET
	int "Callable interface to get instrumentatin data"
	default 2048
	depends on !SCHED_INSTRUMENTATION_CSECTION && (!SCHED_INSTRUMENTATION_SPINLOCK || !SMP)
	---help---
		Add support for interfaces to get the size of the next note and also
		to extract the next note from the instrumentation buffer:

			ssize_t sched_note_get(FAR uint8_t *buffer, size_t buflen);
			ssize_t sched_note_size(void);

		NOTE: This option is not available if critical sections are being
		monitor (nor if spinlocks are being monitored in SMP configuration)
		because there would be a logical error in the design in those cases.
		That error is that these interfaces call enter_ and leave_critical_section
		(and which us spinlocks in SMP mode).  That means that each call to
		sched_note_get() causes several additional entries to be added from
		the note buffer in order to remove one entry.

endif # SCHED_INSTRUMENTATION_BUFFER
endif # SCHED_INSTRUMENTATION
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 at boot-up
		time.  Enables stdout, stderr, stdin in the start-up application.

		You need this setting if your console device is ready at boot time.
		For example, if you are using a serial console, then /dev/console
		(aka, /dev/ttyS0) will be available when the application first starts.

		You must not select DEV_CONSOLE if you console device comes up later
		and is not ready until after the application starts.  At this time,
		the only console device that behaves this way is a USB serial console.
		When the application first starts, the USB is (probably) not yet
		connected and /dev/console will not be created until later when the
		host connects to the USB console.

config FDCLONE_DISABLE
	bool "Disable cloning of file descriptors"
	default n
	---help---
		Disable cloning of all file descriptors by task_create() when a new
		ask 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
	descriptors 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.
		When this option is enabled, the initial configuration of all seamphores
		and mutexes will be with priority inheritance enabled.  That configuration
		may not be appropriate in all cases (such as when the semaphore or mutex
		is used for signaling).  In such cases, priority inheritance be be
		disabled for individual semaphores by calling:

			int ret = sem_setprotocol(&sem, SEM_PRIO_NONE);

		And for individual pthread mutexes by setting the protocol attribute
		before initializing the mutex:

			int ret = pthread_mutexattr_setprotocol(&attr, PTHREAD_PRIO_NONE);

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.

if BOARD_INITIALIZE

config BOARD_INITTHREAD
	bool "Board initialization thread"
	default n
	---help---
		Some initialization operations cannot be performed on the start-up,
		initialization thread.  That is because the initialization thread
		cannot wait for event.  If waiting is required as part of the board
		initialization then this option must be selected.  Waiting may be
		required, for example, to mount a file system or or initialize a
		device such as an SD card.

if BOARD_INITTHREAD

config BOARD_INITTHREAD_STACKSIZE
	int "Board initialization thread stack size"
	default 2048
	---help---
		The size of the stack to allocate when starting the board
		initialization thread.

config BOARD_INITTHREAD_PRIORITY
	int "Board initialization thread priority"
	default 240
	---help---
		The priority of the board initialization thread.  This priority is
		not a critical setting.  No other application threads will be
		started until the board initialization is completed.  Hence, there
		is very little competition for the CPU.

endif # BOARD_INITTHREAD
endif # BOARD_INITIALIZE

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

config SIG_EVTHREAD
	bool "Support SIGEV_THHREAD"
	default n
	depends on BUILD_FLAT && SCHED_WORKQUEUE
	---help---
		Built in support for the SIGEV_THREAD signal deliver method.

		NOTE: The current implementation uses a work queue to notify the
		client.  This, however, would only work in the FLAT build.  A
		different mechanism would need to be development to support this
		feature on the PROTECTED or KERNEL build.

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_POLL
	int "SIGPOLL"
	default 5
	depends on FS_AIO
	---help---
		The SIGPOLL signal is sent to a process when an asynchronous I/O
		event occurs (meaning it has been polled).  Default: 5

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 || LIB_USRWORK
	---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

config MODULE
	bool "Enable loadable OS modules"
	default n
	select LIBC_MODLIB
	select LIBC_ARCH_ELF
	---help---
		Enable support for loadable OS modules.  Default: n

menu "Work queue support"

config SCHED_WORKQUEUE
#	bool "Enable worker thread"
	bool
	default n
	depends on !DISABLE_SIGNALS
	---help---
		Create dedicated "worker" threads to handle delayed or asynchronous
		processing.

config SCHED_HPWORK
	bool "High priority (kernel) worker thread"
	default n
	depends on !DISABLE_SIGNALS
	select SCHED_WORKQUEUE
	---help---
		Create a dedicated high-priority "worker" thread to handle delayed
		processing from interrupt handlers.  This feature is required for
		some drivers but, if there are no complaints, can be safely
		disabled.  The high priority worker thread also performs garbage
		collection -- completing any delayed memory deallocations from
		interrupt handlers.  If the high-priority worker thread is disabled,
		then that clean up will be performed either by (1) the low-priority
		worker thread, if enabled, and if not (2) the IDLE thread instead
		(which runs at the lowest of priority and may not be appropriate if
		memory reclamation is of high priority)

		For other, less-critical asynchronous or delayed process, the
		low-priority worker thread is recommended.

if SCHED_HPWORK

config SCHED_HPWORKPRIORITY
	int "High priority worker thread priority"
	default 224
	---help---
		The execution priority of the higher priority worker thread.

		The higher priority worker thread is intended to serve as the
		"bottom" half for device drivers.  As a consequence it must run at
		a very high, fixed priority.  Typically, it should be the highest
		priority thread in your system.  Default: 224

		For lower priority, application oriented worker thread support,
		please consider enabling the lower priority work queue.  The lower
		priority work queue runs at a lower priority, of course, but has
		the added advantage that it supports "priority inheritance" (if
		PRIORITY_INHERITANCE is also selected):  The priority of the lower
		priority worker thread can then be adjusted to match the highest
		priority client.

config SCHED_HPWORKPERIOD
	int "High priority worker thread period"
	default 100000 if SCHED_LPWORK
	default 50000 if !SCHED_LPWORK
	---help---
		How often the worker thread checks for work in units of microseconds.
		Default:  If the high priority worker thread is performing garbage
		collection, then the default is 50*1000 (50 MS).  Otherwise, if the
		lower priority worker thread is performing garbage collection, the
		default is 100*1000.

config SCHED_HPWORKSTACKSIZE
	int "High priority worker thread stack size"
	default 2048
	---help---
		The stack size allocated for the worker thread.  Default: 2K.

endif # SCHED_HPWORK

config SCHED_LPWORK
	bool "Low priority (kernel) worker thread"
	default n
	depends on !DISABLE_SIGNALS
	select SCHED_WORKQUEUE
	---help---
		If SCHED_LPWORK is defined then a lower-priority work queue will
		be created.  This lower priority work queue is better suited for
		more extended, application oriented processing (such as file system
		clean-up operations or asynchronous I/O)

if SCHED_LPWORK

config SCHED_LPNTHREADS
	int "Number of low-priority worker threads"
	default 1 if !FS_AIO
	default 4 if FS_AIO
	---help---
		This options selects multiple, low-priority threads.  This is
		essentially a "thread pool" that provides multi-threaded servicing
		of the low-priority work queue.  This breaks the serialization
		of the "queue" (hence, it is no longer a queue at all).

		This options is required to support, for example, I/O operations
		that stall waiting for input.  If there is only a single thread,
		then the entire low-priority queue processing stalls in such cases.
		Such behavior is necessary to support asynchronous I/O, AIO (for
		example).

		CAUTION: Some drivers may use the work queue to serialize
		operations.  The may also use the low-priority work queue if it is
		available.  If there are multiple low-priority worker thread, then
		this can result in the loss of that serialization.  There may be
		concurrent driver operations running on different LP threads and
		this could lead to a failure.  You may need to visit the use of the
		LP work queue on your configuration is you select
		CONFIG_SCHED_LPNTHREADS > 1

config SCHED_LPWORKPRIORITY
	int "Low priority worker thread priority"
	default 50
	---help---
		The minimum execution priority of the lower priority worker thread.

		The lower priority worker thread is intended support application-
		oriented functions.  The lower priority work queue runs at a lower
		priority, of course, but has the added advantage that it supports
		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
		The priority of the lower priority worker thread can then be
		adjusted to match the highest priority client.  Default: 50

		NOTE: This priority inheritance feature is not automatic.  The
		lower priority worker thread will always a fixed priority unless
		you implement logic that calls lpwork_boostpriority() to raise the
		priority of the lower priority worker thread (typically called
		before scheduling the work) and then call the matching
		lpwork_restorepriority() when the work is completed (typically
		called within the work handler at the completion of the work).
		Currently, only the NuttX asynchronous I/O logic uses this dynamic
		prioritization feature.

		The higher priority worker thread, on the other hand, is intended
		to serve as the "bottom" half for device drivers.  As a consequence
		it must run at a very high, fixed priority.  Typically, it should
		be the highest priority thread in your system.

config SCHED_LPWORKPRIOMAX
	int "Low priority worker thread maximum priority"
	default 176
	depends on PRIORITY_INHERITANCE
	---help---
		The maximum execution priority of the lower priority worker thread.

		The lower priority worker thread is intended support application-
		oriented functions.  The lower priority work queue runs at a lower
		priority, of course, but has the added advantage that it supports
		"priority inheritance" (if PRIORITY_INHERITANCE is also selected):
		The priority of the lower priority worker thread can then be
		adjusted to match the highest priority client.

		The higher priority worker thread, on the other hand, is intended
		to serve as the "bottom" half for device drivers.  As a consequence
		it must run at a very high, fixed priority.  Typically, it should
		be the highest priority thread in your system.

		This value provides an upper limit on the priority of the lower
		priority worker thread.  This would be necessary, for example, if
		the higher priority worker thread were to defer work to the lower
		priority thread.  Clearly, in such a case, you would want to limit
		the maximum priority of the lower priority work thread.  Default:
		176

config SCHED_LPWORKPERIOD
	int "Low priority worker thread period"
	default 50000
	---help---
		How often the lower priority worker thread checks for work in units
		of microseconds. Default: 50*1000 (50 MS).

config SCHED_LPWORKSTACKSIZE
	int "Low priority worker thread stack size"
	default 2048
	---help---
		The stack size allocated for the lower priority worker thread.  Default: 2K.

endif # SCHED_LPWORK
endmenu # Work Queue Support

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 initial boot of the system up to the
		point where start-up appliation 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 user initialization thread
		that is started as soon as the OS completes its initialization.

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