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cc630028f9
Added header comment Removed issues. The real problem here seemed to be a mutex-unlock without a corresponding lock, which results in undefined behavior according to the docs. Everything seems fine if the lock/unlock are not there or if they both are.
49 lines
1.3 KiB
Scheme
49 lines
1.3 KiB
Scheme
;; An example program having multiple producers concurrently writing to a queue
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;; and a single consumer reading from the queue.
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(import
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(scheme base)
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(scheme read)
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(scheme write)
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(srfi 18))
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;; Global queue and a lock to coordinate access to it.
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;; Note ->heap is used to ensure any objects accessed by multiple threads are
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;; not on a thread's local stack, since those objects can be moved at any time
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;; by the thread's minor GC.
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(define *queue* (->heap (list)))
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(define *lock* (make-mutex))
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(define (producer)
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(let loop ((n 100))
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(cond
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((> n 0)
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(mutex-lock! *lock*)
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(write (cons 'a *queue*))
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(set! *queue* (->heap (cons (->heap n) *queue*)))
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(mutex-unlock! *lock*)
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(loop (- n 1)))
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(else
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(write "producer thread done")))))
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(define (consumer)
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(let loop ()
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;(write (list (null? *queue*) *queue*))
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(define sleep? #f)
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(mutex-lock! *lock*)
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(cond
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((not (null? *queue*))
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(write (car *queue*))
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(set! *queue* (cdr *queue*)))
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(else
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(write "consumer sleeping")
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(set! sleep? #t)))
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(mutex-unlock! *lock*)
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(if sleep? (thread-sleep! 1000))
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(loop)))
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(thread-start! (make-thread producer))
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(thread-start! (make-thread producer))
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(thread-start! (make-thread producer))
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;(producer)
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(consumer)
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;(read)
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