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barrier-block-and-wait

The function barrier-block-and-wait enables the barrier barrier with t, that is it makes any number of arrivers wait, and then waits until count arrivers arrive.

wait-if-used-p controls whether to wait if another process is already inside barrier-block-and-wait. The default value of wait-if-used-p is nil.

barrier is a barrier made by make-barrier.

errorp controls whether to signal an error if another process is already inside barrier-block-and-wait and wait-if-used-p is nil. The default value of errorp is nil.

timeout, if non-nil, specifies the time in seconds to wait before timing out. The default value of timeout is nil.

unblock specifies whether processes that already wait on barrier should be unblocked first. The default value of unblock is nil.

barrier-block-and-wait is "using" barrier, and only one process can do this the same time. barrier-block-and-wait first tries to mark barrier as used by the current process, which will fail if another process is inside barrier-block-and-wait with the same barrier. In this case it does one of three options:

1. If wait-if-used-p is non-nil, it calls barrier-wait on barrier (without any keyword argument) and returns the result.
2. If errorp is non-nil, it calls error.
3. Otherwise is returns the other process.

Once barrier-block-and-wait has successfully marked barrier as used, it changes its count to t as if by calling (barrier-change-count barrier t), which will cause other barrier-wait calls to wait. If unblock is non-nil, it first unblocks all processes that wait on the barrier, so the effect is the same as (barrier-enable barrier t).

It then waits until the arriver count of barrier is greater than or equal to count, or, if timeout is supplied, timeout seconds passed. It then returns the number of arrivers.

result can be one of three types:

integer

The call was successful, and result is the number of arrivers.

symbol

barrier was in use, and wait-if-used-p is non-nil, so barrier-wait was called. result is the result of barrier-wait.

mp:process

barrier is in use, and result is the process that uses it.

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