|
Bigloo supports multithreaded programming. Two different libraries
programming are available. The first one, the Fair Thread
(see Section Fair Threads), enables, simple, easy to develop and
to maintain code. The second one, the Posix Thread
(see Section Posix Threads) enables more
easily to take benefit of the actual parallelism that is now available
on stock hardware. Because it is easier to program with fthread
than with pthread , we strongly recommend to use the former
as much as possible and leave the former for specially demanding
applications. Both libraries are described in this chapter.
10.1 Thread Common Functions
|
This section describes the functions that are available independently
of the multi-threading library.
mutex? obj | SRFI-18 function |
make-mutex [name ] | SRFI-18 function |
mutex-name mutex | SRFI-18 function |
mutex-specific mutex | SRFI-18 function |
mutex-specific-set! mutex obj | SRFI-18 function |
mutex-state mutex | SRFI-18 function |
mutex-lock! mutex [timeout [thread ]] | SRFI-18 function |
mutex-unlock! mutex | SRFI-18 function |
(let ((m (make-mutex)))
(thread-start!
(make-thread (lambda ()
(let loop ()
(if (mutex-lock! m 0)
(begin
(display "locked")
(mutex-unlock! m))
(begin
(thread-yield!)
(loop))))))))
-| locked
(let ((res '()))
(define (mutex-lock-recursively! mutex)
(if (eq? (mutex-state mutex) (current-thread))
(let ((n (mutex-specific mutex)))
(mutex-specific-set! mutex (+ n 1)))
(begin
(mutex-lock! mutex)
(mutex-specific-set! mutex 0))))
(define (mutex-unlock-recursively! mutex)
(let ((n (mutex-specific mutex)))
(if (= n 0)
(mutex-unlock! mutex)
(mutex-specific-set! mutex (- n 1)))))
(thread-start!
(make-thread
(lambda ()
(let ((m (make-mutex)))
(mutex-lock-recursively! m)
(mutex-lock-recursively! m)
(mutex-lock-recursively! m)
(set! res (cons (mutex-specific m) res))
(mutex-unlock-recursively! m)
(mutex-unlock-recursively! m)
(mutex-unlock-recursively! m)
(set! res (cons (mutex-specific m) res))))))
res)
=> (0 2)
|
|
with-lock mutex thunk | Bigloo function |
The function with-lock evaluates the body of the thunk .
The mutex mutex is acquired and released before thunk gets invoked.
The function with-lock might be implemented as:
(define (with-lock mutex thunk)
(mutex-lock! mutex)
(unwind-protect
(thunk)
(mutex-unlock! mutex)))
|
|
condition-variable? obj | SRFI-18 function |
make-condition-variable [name ] | SRFI-18 function |
condition-variable-name cv | SRFI-18 function |
condition-variable-specific cv | SRFI-18 function |
condition-variable-specific-set! cv obj | SRFI-18 function |
condition-variable-wait! cv mutex | SRFI-18 function |
condition-variable-signal! cv | SRFI-18 function |
condition-variable-broadcast! cv | SRFI-18 function |
(let ((res 0))
(define (make-semaphore n)
(vector n (make-mutex) (make-condition-variable)))
(define (semaphore-wait! sema)
(mutex-lock! (vector-ref sema 1))
(let ((n (vector-ref sema 0)))
(if (> n 0)
(begin
(vector-set! sema 0 (- n 1))
(mutex-unlock! (vector-ref sema 1)))
(begin
(mutex-unlock! (vector-ref sema 1) (vector-ref sema 2))
(semaphore-wait! sema)))))
(define (semaphore-signal-by! sema increment)
(mutex-lock! (vector-ref sema 1))
(let ((n (+ (vector-ref sema 0) increment)))
(vector-set! sema 0 n)
(if (> n 0)
(condition-variable-broadcast! (vector-ref sema 2)))
(mutex-unlock! (vector-ref sema 1))))
(let ((sema (make-semaphore 10)))
(let ((t1 (thread-start! (make-thread
(lambda ()
(semaphore-wait! sema)
(set! res (current-time))))))
(t2 (thread-start! (make-thread
(lambda ()
(let loop ((n 10))
(if (> n 0)
(begin
(semaphore-signal-by! sema 1)
(thread-yield!)
(loop (- n 1))))))))))
(scheduler-start!)
res)))
=> 2
|
|
thread-parameter ident | Bigloo function |
Returns the value of the parameter ident in the current thread. If
no value is bound to this parameter, #f is returned.
A thread parameter is implemented by a chunk of memory specific to
each thread. All threads are created with an empty set of parameters.
|
thread-parameter-set! ident value | Bigloo function |
Associates a value to a parameter named ident .
|
Bigloo supports fair threads (see Section Thread), a
specification of cooperative threads. In this framework a thread must
explicitly or implicitly yield the processor to the scheduler
(see Section Scheduler). Explicit cooperation is achieved by
library functions such as thread-yield! or
thread-sleep! . The scheduler does not preempt a running thread to
allocate the processor to another waiting thread. Fair threads have two
drawbacks over preemptive threads: - Cooperative threads are not skilled to benefit of multi processors
platforms.
- Single threads programs must be adapted in order to be ran
concurrently.
On the other hand, Fair threads have advantages that make them
suitable for a high level programming language such as Scheme: - Fair threads have a strong and well defined semantic. Multi threaded
programs using Fair threads are deterministic thus programs
that deploy Fair threads are predictable.
- Fair threads are easier to program with because they hide most the
of the concurrent programming pitfalls. In particular, since Fair
threads enforce a strong synchronization, there
is no need to deploy techniques such as mutex, semaphore
or condition variables.
This whole chapter has been written in collaboration with Frédéric
Boussinot. It uses materials on Fair threads that can be found at
http://www-sop.inria.fr/mimosa/rp/FairThreads/html/FairThreads.html.
10.2.1 Introduction to Fair Threads
|
Fair threads are cooperative threads run by a fair scheduler which
gives them equal access to the processor. Fair threads can communicate
using broadcast events. Their semantics does not depends on the
executing platform. Fine control over fair threads execution is
possible allowing the programming of specific user-defined scheduling
strategies. Contrary to standard sequential programming where the processor
executes a single program, in concurrent programming the processor is
a shared resource which is dispatched to several programs. The term
concurrent is appropriate because programs can be seen as
concurrently competing to gain access to the processor, in order to
execute. Threads are a basic mean for concurrent programming, and are widely
used in operating systems. At language level, threads offer a way to
structure programs by decomposing systems in several concurrent
components; in this respect, threads are useful for modularity. However, threads are generally considered as low-level primitives
leading to over-complex programming. Moreover, threads generally have
loose semantics, in particular depending on the underlying executing
platform; to give them a precise semantics is a difficult task, and
this is a clearly identified problem to get portable code. Bigloo proposes a new framework with clear and simple semantics, and
with an efficient implementation. In it, threads are called
fair; basically a fair thread is a cooperative thread executed
in a context in which all threads always have equal access to the
processor. Fair threads have a deterministic semantics, relying on
previous work belonging to the so-called reactive approach.
Bigloo uses a set of primitive functions to create, run and
handle thread. For the sake of standardization the name and semantic
of SRFI-18 (Multithreading support) has been used. This section presents
only the mandatory functions to program with Fair threads in Bigloo. The
Section SRFI-18 presents the functions that are not necessary
to Bigloo but supported for compliance with SRFI-18.
10.2.2.1 Thread
current-thread | SRFI-18 function |
Returns the current thread.
|
thread? obj | SRFI-18 function |
Returns #t if obj is a thread, otherwise returns #f .
|
make-thread thunk [name ] | SRFI-18 function |
Returns a new thread which is not started yet. The body of the thread
is the body of the procedure thunk . The optional argument name
can be use to identify the thread. It can be any Bigloo value.
(make-thread (lambda () (print 1) (thread-yield!) (print 2)) 'my-thread)
|
|
thread-start! thread [scheduler ] | SRFI-18 function |
Runs a thread created with make-thread . If scheduler is
provided, the thread is started this particular scheduler. Otherwise,
it is started in the current scheduler (see Section Scheduler).
Threads are started at the beginning of reactions
(see Section Scheduler).
|
thread-name thread | SRFI-18 function |
Returns the name of the thread that has been passed to
make-thread .
|
thread-specific thread | SRFI-18 function |
thread-specific-set! thread obj | SRFI-18 function |
Returns and sets value in the specific field of the thread . If no
value has been set, thread-specific returns an unspecified value.
(let ((t (make-thread (lambda ()
(print (thread-specific (current-thread)))))))
(thread-specific-set! t 'foo)
(thread-start! t)) -| foo
|
|
thread-cleanup thread | Bigloo function |
thread-cleanup-set! thread fun | Bigloo function |
Associates a cleanup function to a thread. The cleanup function is called
with the thread itself. The cleanup function is executed
in a context where current-thread is the thread owning the
cleanup function.
(let ((t (make-thread (lambda () 'done) 'foo)))
(thread-cleanup-set! t (lambda (v) (print (thread-name (current-thread))
", exit value: " v)))
(thread-start! t)) -| foo, exit value: done
|
|
thread-yield! | SRFI-18 function |
The current thread cooperates. That is, it is suspend for the
reaction and the scheduler selects a new thread to be resumed. The
scheduler resumes the next avaliable thread. If there is only one
thread started in the scheduler, the same thread is resumed.
A reaction correspond to the invocation of a scheduler-react!
call (see Section Scheduler).
|
thread-sleep! timeout | SRFI-18 function |
The current thread cooperates during exactly timeout
reactions (see Scheduler). It is suspended and the scheduler
selects a new thread to be resumed. If there is only one thread started in the
scheduler, the same thread will be resumed.
(let ((t1 (make-thread
(lambda () (thread-sleep! 2) (display 'foo))))
(t2 (make-thread
(lambda () (let loop ((n 1))
(display n)
(thread-yield!)
(if (< n 5)
(loop (+ n 1))))))))
(thread-start! t1)
(thread-start! t2)
(scheduler-start!)) -| 12foo34
|
|
thread-terminate! thread | SRFI-18 function |
Terminates thread at the end of the current reaction.
|
thread-join! thread [timeout [timeout-val ]] | SRFI-18 function |
The current thread waits until the thread terminates or until
the timeout is reached (when supplied). If the timeout is
reached, thread-join! returns timeout-val . If thread
terminates, thread-join! returns the end-result of the thread
or the end-exception if that thread terminates abnormally.
If several threads wait for the termination of the same thread, they are
all notified of the termination during the current reaction.
(let* ((t1 (thread-start!
(make-thread (lambda ()
(thread-sleep! 3)
'foo))))
(t2 (thread-start!
(make-thread (lambda ()
(print "t1: " (thread-join! t1 1))))))
(t3 (thread-start!
(make-thread (lambda ()
(print "t2: " (thread-join! t1 2 'bar))))))
(t3 (thread-start!
(make-thread (lambda ()
(print "t3: " (thread-join! t1))))))
(t4 (thread-start!
(make-thread (lambda ()
(print "t4: " (thread-join! t1)))))))
(scheduler-start!))
-| t1: #|%uncaught-exception [reason: (exception . join-timeout)]|
t2: bar
t3: foo
t4: foo
|
|
thread-suspend! thread | Bigloo function |
thread-resume! thread | Bigloo function |
Suspends/resumes the thread at the end of reaction. While suspended
a thread is not eligible to get the processor by the scheduler.
|
thread-await! signal [timeout ] | Bigloo function |
Blocks the thread until signal has been broadcast or until
timeout is elapsed. The function thread-await! returns
the value associated with the previous emissions of the signal that
took place during the reaction.
(let ((t1 (thread-start!
(make-thread
(lambda ()
(display (thread-await! 'foo))
(display (thread-await! 'bar))))))
(t2 (thread-start!
(make-thread
(lambda ()
(broadcast! 'foo 'val1-foo)
(broadcast! 'foo 'val2-foo)))))
(t3 (thread-start!
(make-thread
(lambda ()
(thread-sleep! 2)
(broadcast! 'bar 'val-bar))))))
(let loop ((n 1))
(display n)
(scheduler-react! (default-scheduler))
(loop (+ n 1))))
-| 1val2-foo23val-bar456...
|
The function thread-await! cannot be used to intercept all the signals
broadcasted during a reaction. This is illustrated by the following example
were obviously thread-await! cannot intercept the emission of the
signal:
(thread-start! (make-thread (lambda ()
(tread-await! 'foo)
(broadcast! 'foo 1))))
(thread-start! (make-thread (lambda ()
(broadcast! 'foo 2))))
|
|
thread-get-values! signal | Bigloo function |
Terminates the instant for the thread (as thread-yield! ) and
returns, hence at the next instant, all the values associated with
broadcast signal (see Section Signal) during the previous scheduler
reaction (see Section Scheduler).
Example:
(thread-start! (make-thread
(lambda ()
(for-each print (thread-get-values! 'foo)))))
(thread-start! (make-thread
(lambda ()
(broadcast! 'foo 1)
(broadcast! 'foo 'foo)
(broadcast! 'foo "blabla"))))
-| 1
foo
blabla
|
Example:
(let ((t1 (thread-start!
(make-thread
(lambda ()
(for-each print (thread-get-values! 'foo)))
't1)))
(t2 (thread-start!
(make-thread
(lambda ()
(broadcast! 'foo (current-thread))
(thread-yield!)
;; this second broadcast won't be intercepted
;; because it occurs during the next reaction
(broadcast! 'foo (current-thread)))
't2)))
(t3 (thread-start!
(make-thread
(lambda ()
(broadcast! 'foo (current-thread))
(broadcast! 'foo (current-thread)))
't3))))
(scheduler-start!))
-| #<thread:t2>
#<thread:t3>
#<thread:t3>
|
|
thread-await-values! signal [timeout ] | Bigloo function |
This blocks the current thread until signal has been broadcast.
It then returns, at the next instant, all the values associated with
all the broadcasts that took place during the instant.
It can be defined as:
(define (thread-await-values! signal . tmt)
(apply thread-await! signal tmt)
(thread-get-values signal))
|
|
thread-await*! signals [timeout ] | Bigloo function |
Wait for one of a list of signals. The function thread-await*!
can be compared to the Unix select function. The argument
signals is a list of signal identifier. The function
thread-await*! blocks the current thread until one of the signal in
the list signals is broadcast or until the optional numerical argument
timeout is elapsed. If the thread unblocks because the timeout is
elapsed, thread-await*! returns #f . Otherwise it returns two
values that have to be collected with multiple-value-bind (see
Control Features). The first one is the value of the broadcast
signal. The second one is the broadcast signal.
Example:
(let ((res #f))
(thread-start!
(make-thread (lambda ()
(let ((sig* (list 'foo 'bar)))
(multiple-value-bind (val1 sig1)
(thread-await*! sig*)
(multiple-value-bind (val2 sig2)
(thread-await*! sig*)
(thread-yield!)
(multiple-value-bind (val3 sig3)
(thread-await*! sig*)
(set! res (list sig1 sig2 sig3)))))))))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 2)
(broadcast! 'foo 1))))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 3)
(broadcast! 'bar 2))))
(scheduler-start!)
res)
=> '(foo foo bar)
|
A second example using timeouts:
(let ((res #f))
(thread-start!
(make-thread (lambda ()
(let ((sig* (list 'foo 'bar)))
(multiple-value-bind (val1 sig1)
(thread-await*! sig* 1)
(thread-yield!)
(multiple-value-bind (val2 sig2)
(thread-await*! sig* 1)
(thread-yield!)
(multiple-value-bind (val3 sig3)
(thread-await*! sig* 2)
(set! res (list sig1 sig2 sig3)))))))))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 2)
(broadcast! 'foo 1))))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 3)
(broadcast! 'bar 2))))
(scheduler-start!)
res)
=> '(#f foo bar)
|
|
thread-get-values*! signals | Bigloo function |
Terminates the instant for the thread (as thread-yield! ) and
returns, hence at the next instant, all the values associated with
all broadcast signals (see Section Signal) during the previous
scheduler reaction (see Section Scheduler). The function
thread-get-values*! returns an alist made of the scanned signal
and their values. That is the length of the returns list is the length
of the list signals . If a signal of the list signals has not
been broadcast, its associated entry the list returned by
thread-get-values*! has an empty cdr .
Example:
(let ((s1 'foo)
(s2 'bar)
(s3 'gee)
(res #f))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 2)
(broadcast! 'foo (current-time))
(broadcast! 'bar 0))))
(thread-start!
(make-thread (lambda ()
(thread-await*! (list s1 s2 s3))
(set! res (thread-get-values*! (list s1 s2 s3))))))
(thread-start!
(make-thread (lambda ()
(thread-sleep! 2)
(broadcast! 'bar (current-time)))))
(scheduler-start!)
res)
=> ((foo 3) (bar 3 0) (gee))
|
Used with asynchronous signal, the functions thread-await*! and
thread-get-values*! can be used to read concurrently, in a non
blocking way, several files.
|
thread-await-values*! signals [timeout ] | Bigloo function |
This blocks the current thread until at least one of signals has
been broadcast. It then returns, at the next instant, all the values associated
with all the broadcasts that took place during the instant. It can be
defined as:
(define (thread-await-values*! signal . tmt)
(apply thread-await*! signal tmt)
(thread-get-values*! signal))
|
|
10.2.2.2 Scheduler
make-scheduler [envs ] | Bigloo function |
Creates a new scheduler. The optional arguments envs are
fair thread environments which will be defined in forthcoming
Bigloo releases.
|
scheduler? obj | Bigloo function |
Returns #t if obj is a scheduler. Otherwise returns #f .
|
current-scheduler | Bigloo function |
Returns the current scheduler. The current scheduler is the scheduler
used in the last call to scheduler-react! or scheduler-start! .
It always exists a current scheduler. That is, it is optional for an
application to create a scheduler.
|
scheduler-react! [scheduler ] | Bigloo function |
Executes all the treads started (see thread-start! ,
Section Thread) in the scheduler until all the threads are
blocked. A thread is blocked if the has explicitly yield the processor
(thread-yield! and thread-sleep! ) or because it is waiting
a signal (thread-await! ). A thread
can be selected several times during the same reaction.
The function scheduler-react! returns a symbol denoting the
state of the scheduler. The possible states are:
ready The Scheduler is ready to execute some threads.
done All the threads started in the scheduler have terminated.
await All the threads started in the scheduler are waiting for
a signal.
An invocation of scheduler-react! is called a reaction.
|
scheduler-start! [arg [scheduler ]] | Bigloo function |
Executes scheduler-react! as long as the scheduler is not done.
If the optional argument scheduler is not provided,
scheduler-start! uses the current scheduler
(see current-scheduler ). The optional arg can either be:
- An integer standing for the number of times
scheduler-react!
must be called.
- A procedure
f of one argument. The procedure f
is invoked after each reaction. It is passed a value i which is
the iteration number of the scheduler. The reactions of the scheduler
are stopped when f returns #f .
(let* ((s (make-scheduler))
(t (make-thread (lambda ()
(let loop ((n 0))
(display n)
(thread-yield!)
(loop (+ 1 n)))))))
(scheduler-start! 10 s))
-| 0123456789
(let* ((s (make-scheduler))
(t (make-thread (lambda ()
(let loop ((n 0))
(display n)
(thread-yield!)
(loop (+ 1 n)))))))
(scheduler-start! (lambda (i) (read-char)) s))
-| 0123456789
|
|
scheduler-terminate! [scheduler ] | Bigloo function |
Terminates all the threads in scheduler .
|
scheduler-instant [scheduler ] | Bigloo function |
Returns the current reaction number of scheduler . The reaction
number is the number of times scheduler-react! has been invoked
passing scheduler as argument.
|
10.2.2.3 Signal
broadcast! signal [val ] | Bigloo function |
Broadcasts signal to all threads started in scheduler
immediately, that is during the reaction. This function can only
be called from within a running thread. If the optional argument val
is omitted, the signal is broadcast with an unspecified value.
(thread-start! (make-thread
(lambda ()
(thread-await! 'foo)
(print (scheduler-instant (current-scheduler))))))
(thread-start! (make-thread
(lambda ()
(broadcast! 'foo))))
(scheduler-start!)
-| 1
|
|
scheduler-broadcast! scheduler signal [val ] | Bigloo function |
At the next react broadcasts signal to all threads started
in scheduler . This is used to impact running threads from outside
any threads. If the optional argument val
is omitted, the signal is broadcast with an unspecified value.
|
make-asynchronous-signal proc | Bigloo function |
This function invokes in the background, the procedure proc .
This function takes one parameter which is the signal that is broadcast
when the invocation returns. When the host operating system supports
parallel executions, the invocation of proc is executed in
parallel with the waiting thread.
Asynchronous signals can be used to implement non blocking system
operations, such as input/output. Here is an example that illustrates
how to implement concurrent programs that behaves similarly with
Fair Threads and Posix Threads.
(define-expander read
(lambda (x e)
(cond-expand
(fthread
(thread-await!
(make-aynchronous-signal
(lambda (s)
(read ,@(map (lambda (x) (e x e)) (cdr x)))))))
(else
`(read ,@(map (lambda (x) (e x e)) (cdr x)))))))
|
|
Bigloo implements SRFI-18 (Multithreading support). This SRFI is
available at http://srfi.schemers.org/srfi-18/srfi-18.html. One
should keep in mind that since the Bigloo scheduler is cooperative
Bigloo threads must cooperate at some point in order not to
block the execution of other threads. The functions enforcing
cooperation are thread-yield! , thread-sleep! ,
thread-join! and thread-await! . In addition the SRFI-18
mutex-unlock function enforce cooperation. Thread locking mechanism is common to Fair Threads and Posix Threads
(see Thread Common Functions).
current-time [scheduler ] | SRFI-18 function |
Returns the reaction number of scheduler .
|
time? obj | SRFI-18 function |
time->seconds obj | SRFI-18 function |
|
join-timeout-exception? obj | SRFI-18 function |
abandoned-mutex-exception? obj | SRFI-18 function |
terminated-thread-exception? obj | SRFI-18 function |
uncaught-exception? obj | SRFI-18 function |
uncaught-exception-reason exc | SRFI-18 function |
|
This section describes the Posix-Like multi-threading Bigloo library.
As much as possible, the names exported by this library are compatible
with the Fair Threads library (see Section Fair Threads).
10.3.1 Using Posix Threads
|
The Bigloo modules initialization model does not permit to create threads
before the main function is started. In other words, it is unsafe
to use the Posix Threads API at the top level of modules. On some particular
applications this might work correctly. On other it could produce
an error message stating the threads cannot be created or started before
the pthread library is initialized.
thread? obj | SRFI-18 function |
Returns #t if obj is a thread, otherwise returns #f .
|
current-thread | SRFI-18 function |
Returns the thread currently running.
|
make-thread thunk [name ] | SRFI-18 function |
Returns a new thread which is not started yet. The body of the thread
is the body of the procedure thunk . The optional argument name
can be use to identify the thread. It can be any Bigloo value.
(module example
(library pthread)
(main main))
(define (main argv)
(make-thread
(lambda ()
(print 1)
(thread-yield!)
(print 2))
'my-thread))
|
|
thread-start! thread | SRFI-18 function |
thread-start-joinable! thread | SRFI-18 function |
Runs a thread created with make-thread .
|
thread-name thread | SRFI-18 function |
Returns the name of the thread that has been passed to
make-thread .
|
thread-specific thread | SRFI-18 function |
thread-specific-set! thread obj | SRFI-18 function |
Returns and sets value in the specific field of the thread . If no
value has been set, thread-specific returns an unspecified value.
(let ((t (make-thread (lambda ()
(print (thread-specific (current-thread)))))))
(thread-specific-set! t 'foo)
(thread-start! t)) -| foo
|
|
thread-cleanup thread | Bigloo function |
thread-cleanup-set! thread fun | Bigloo function |
Associates a cleanup function to a thread. The cleanup function is called
with the thread itself. The cleanup function is executed
in a context where current-thread is the thread owning the
cleanup function.
(let ((t (make-thread (lambda () 'done) 'foo)))
(thread-cleanup-set! t (lambda (v) (print (thread-name (current-thread))
", exit value: " v)))
(thread-start! t)) -| foo, exit value: done
|
|
thread-yield! | SRFI-18 function |
The current thread cooperates.
|
thread-sleep! timeout | SRFI-18 function |
The current thread sleeps for a certain period. It is suspended
and the scheduler is free to select a new thread to be resumed. If
there is only one thread started in the scheduler, the same thread
will be resumed. The time of timeout is used to determine the
time the thread must sleep.
Here are the possible types for timeout .
date : the thread sleeps at least until the date timeout .
real : the thread sleeps at least timeout seconds.
fixum , elong , llong : the thread sleeps at least
timeout milli-seconds.
|
thread-terminate! thread | SRFI-18 function |
Terminates thread as soon as possible.
|
thread-join! thread | SRFI-18 function |
The current thread waits until the thread terminates. If thread
terminates, thread-join! returns the end-result of the thread
or the end-exception if that thread terminates abnormally.
It is possible to wait for the termination of the a thread if and only if
it has been started with thread-start-joinable! . In particular,
threads started with thread-start cannot be joined.
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terminated-thread-exception? obj | SRFI-18 function |
uncaught-exception? obj | SRFI-18 function |
uncaught-exception-reason exc | SRFI-18 function |
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10.3.4 Condition Variables
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Posix thread condition variables follows the common thread API
(see Thread Common Functions).
(module example
(library pthread)
(main argv))
(define (main argv)
(let ((res #f)
(lock (make-mutex))
(cv (make-condition-variable)))
(let* ((th1 (thread-start-joinable!
(make-thread
(lambda ()
(mutex-lock! lock)
(condition-variable-wait! lock cv)
(mutex-unlock! lock)
(set! res 23)))))
(th2 (thread-start!
(make-thread
(lambda ()
(mutex-lock! lock)
(condition-variable-signal! cv)
(mutex-unlock! lock))))))
(thread-join! th1))
res))
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