[GHC] #7216: Compositional blocking on file descriptors

[GHC]

#7216: Compositional blocking on file descriptors
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 Reporter:  AndreasVoellmy    |          Owner:                  
     Type:  feature request   |         Status:  new             
 Priority:  normal            |      Component:  libraries/base  
  Version:  7.4.2             |       Keywords:                  
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  None/Unknown      |       Testcase:                  
Blockedby:                    |       Blocking:                  
  Related:                    |  
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 The GHC.Event.Thread module provides threadWaitRead, threadWaitWrite :: Fd
 -> IO () calls that block until a particular file descriptor is ready for
 reading or writing. With this API a single thread cannot wait on multiple
 file descriptors or a file descriptor and some other condition (e.g. an
 MVar, STM transaction, etc). One could work around this by creating extra
 producer threads that each monitor one file descriptor and then multiplex
 messages from those threads onto a single channel (or mvar, etc) and then
 have a consumer thread that waits on this single multiplexed channel.
 Unfortunately, this extra indirection imposes a modest performance penalty
 in the form of longer wait times to service events due to having to switch
 between multiple threads to handle a single ready file.

 I propose to provide analogous functions in the STM monad
 threadWaitReadSTM,threadWaitWriteSTM :: Fd -> STM (). These will allow a
 single thread to wait on multiple files or both files and other
 conditions. This eliminates the switching between threads to service a
 request.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7216>
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