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sof authored
Asynchronous / non-blocking I/O for Win32 platforms. This commit introduces a Concurrent Haskell friendly view of I/O on Win32 platforms. Through the use of a pool of worker Win32 threads, CH threads may issue asynchronous I/O requests without blocking the progress of other CH threads. The issuing CH thread is blocked until the request has been serviced though. GHC.Conc exports the primops that take care of issuing the asynchronous I/O requests, which the IO implementation now takes advantage of. By default, all Handles are non-blocking/asynchronous, but should performance become an issue, having a per-Handle flag for turning off non-blocking could easily be imagined&introduced. [Incidentally, this thread pool-based implementation could easily be extended to also allow Haskell code to delegate the execution of arbitrary pieces of (potentially blocking) external code to another OS thread. Given how relatively gnarly the locking story has turned out to be with the 'threaded' RTS, that may not be such a bad idea.]
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