Threads

Threads

Threads allow for expressing concurrent programs. The assumed model is shared memory with explicit synchronization and symmetric multiprocessing and is based heavily upon pthreads This section is preliminary and might change in the future. There are several limitations in the current implementation. It represents a rudimentary but usable subset of typical thread operations. Tables and vectors require user locks to ensure thread safety and no out of language crashes. Finally, the compiler, interpreter, and (re)definition machinery are thread unsafe and can only reliably be run in one thread.

<thread>	(<any>)	C
	Represents a thread of executation schedulable across multiple processors. Upon creation executes thread-function in separate thread.
thread-name	(thread|<thread> => (t? <sym>))	P
thread-priority	(thread|<thread> => <int>)	P
thread-function	(thread|<thread> => <fun>)	P
new	(x|(t< <thread>) inits|... => <thread>)	M
	Creates thread and runs thread-function of created thread in separate OS thread.
SPAWN	(SPAWN ,@body)	S
	== (FAB <thread> thread-function (fun () ,@body))
thread-yield	()	M
	Surrenders processor to another thread.
thread-join	(thread|<thread>)	M
	Causes current thread to wait for the termination of thread.
thread-current	(=> <thread>)	M
all-threads	(=> <tup>)	M
sleep	(secs|<flo>)	M
	Pauses current thread for secs seconds.
<lock>	(<any>)	C
	Represents a mutex.
lock-name	(lock|<lock> => (t? <sym>))	P
new	(x|(t< <lock>) inits|... => <lock>)	M
lock-lock	(lock|<lock>)	M
	Obtain exclusive access to lock waiting if necessary.
lock-unlock	(lock|<lock>)	M
	Free up exclusive access to lock potentially allowing another thread access.
WITH-LOCK	(WITH-LOCK ,lock ,@body)	S
	== (FIN (SEQ (lock-lock ,lock) ,@body) (lock-unlock ,lock))
<event>	(<any>)	C
	Represents a condition variable used for interthread notification.
event-name	(event|<event> => (t? <sym>))	P
new	(x|(t< <event>) inits|... => <event>)	M
event-signal	(event|<event> lock|<lock>)	M
	Unblocks at least one thread waiting on event.
event-broadcast	(event|<event> lock|<lock>)	M
	Unblocks all threads waiting on event.
event-wait	(event|<event> lock|<lock> => <log>)	M
	Unlocks lock and places thread in waiting state to be resumed when event is signaled or broadcasted upon which time lock is reacquired and thread resumed.
event-wait-timed	(event|<event> lock|<lock> secs|<flo> => <log>)	M
	Unlocks lock and places thread in waiting state to be resumed when event is signaled or broadcasted or timeout secs is reached upon which time lock is reacquired and thread resumed.
DDV	(DDV ,var ,form)	S
	Defines a thread local variable named (var-name ,var) with an initial value ,form.
DLET	(DLET ((,var ,val) ...) ,@body)	S
	== (LET ((,old-var ,var) ...) (FIN (SEQ (SET ,var ,val) ... ,@body) (SET ,var ,old-var) ...))
<pipe>	(<flat> <seq!>)	C
	Represents a synchronized FIFO queue allowing multiple readers and writers in separate threads.
enq!	(pipe|<pipe> x => <pipe>)	M
	Adds x to pipe.
deq!	(pipe|<pipe> => <any>)	M
	Removes and returns element from pipe or waits for one to be available.

Threads