Function

Summary

Returns a new barrier.

Package

mp

Signature

make-barrier count &key discount-on-abort discount-on-timeout callback disable-on-unblock name => barrier

Arguments

count

A positive fixnum or t .

name

A string.

Values

barrier

A barrier.

Description

The function make-barrier returns a new barrier with count count .

count can be t , which is interpreted as most-positive-fixnum .

The barrier has the name name , which is useful for debugging but is not used otherwise. If name is omitted, then a default name is generated that is unique among all such default names.

discount-on-timeout and discount-on-abort determine the default behavior when a thread times out or aborts while in the function barrier-wait. See the documentation for barrier-wait.

If disable-on-unblock is true, then barrier-wait will disable the barrier by default when it unblocks it. See disable-on-unblock in the documentation for barrier-wait.

callback is called by barrier-wait just before it unblocks the barrier. It is called with a single argument (the barrier) while holding an internal lock on the barrier that will prevent other operations on the barrier from running. The callback is guaranteed to happen before barrier-wait allows any of the other threads to continue.

Notes

Because the callback is called inside a lock, you should ensure that it is relatively short to prevent congestion if another thread tries to access the barrier. Allocating a few objects is reasonable. If there is a more expensive operation that has to be done by only one of the threads, it can be done by the thread that returned :unblocked from barrier-wait. The advantage of using the callback is that it is called before any of the waiting threads pass the barrier.

See also

barrier-wait