Re: Asynchronous exceptions and laziness bugs in Control.Concurrent.QSem/QSemN

29 Mar 2010

      I just created a ticket for this so it's not forgotten:

http://hackage.haskell.org/trac/ghc/ticket/3944

Bas

On Thu, Mar 18, 2010 at 9:54 PM, Bas van Dijk  wrote:
...
Hello,
after discovering the bugs regarding asynchronous exceptions and
laziness in Data.Unique and Control.Concurrent.SampleVar I became a
bit suspicious about the other concurrency mechanisms.
It looks like Control.Concurrent.Chan is safe because it uses
modifyMVar_ internally which performs the necessary block.
Control.Concurrent.QSem and QSemN are not alright however! They both
suffer the same bugs:
* Potential dead-lock due to not blocking asynchronous exceptions.
* Potential space-leak because of lazily putting numeric expression in a MVar.
The attached patch fixes these bugs.
regards,
Bas