CL-USER> (flet ((foo () (dotimes (i 50) (print i) (sleep .1))))
           (bt:make-thread #'foo)
           (bt:make-thread #'foo))

0
#<SB-THREAD:THREAD "Anonymous thread" waiting on: #<MUTEX "buffer write lock" (free)> {1014EE4E53}>
 
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CL-USER> (flet ((foo () (dotimes (i 50) (print i) (finish-output) (sleep .1))))
           (bt:make-thread #'foo)
           (bt:make-thread #'foo))

0 
0 
#<SB-THREAD:THREAD "Anonymous thread" RUNNING {10150944B3}>


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