Scheme Request for Implementation 230,
by Marc Nieper-Wißkirchen,
is now available for discussion.
Its draft and an archive of the ongoing discussion are available at
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Here's the abstract:
This SRFI defines atomic operations for the Scheme programming
language. An atomic operation is an operation that, even in the
presence of multiple threads, is either executed completely or not
at all. Atomic operations can be used to implement mutexes and
other synchronization primitives, and they can be used to make
concurrent algorithms lock-free. For this, this SRFI defines two
data types, atomic flags and atomic (fixnum) boxes, whose contents
can be queried and mutated atomically. Moreover, each atomic
operation comes with a memory order that defines the level of
synchronization with other threads.