[Haskell-cafe] Re: sendfile leaking descriptors on Linux?

Jeremy Shaw wrote:

On Wed, Feb 17, 2010 at 2:36 AM, Taru Karttunen wrote:

So for sendfile, instead of threadWaitWrite we could do:

r <- timeout (60 * 10^6) threadWaitWrite case r of Nothing -> ... -- timed out (Just ()) -> ... -- keep going

For sendfile, a timeout of 1 second would probably be fine. The *ONLY* purpose of threadWaitWrite in the sendfile code is to avoid busy-waiting on EAGAIN from the native sendfile. What would work is, instead of using threadWaitRead (as in the code you supplied) to simply have a 1 second timeout which causes the loop to call the native sendfile again. Native sendfile *will* fail with an error code if the socket has been disconnected. With that in place "dead" threads waiting on threadWaitWrite will only linger at most 1 second before discovering the disconnect. Not ideal, but a lot better than the current situation.

Does that sound like the right fix to you?

[--snip--]

(Obviously, if people are using sendfile with something other than happstack, it does not help them, but it sounds like trying to fix things in sendfile is misguided anyway.)

How so? As a user I expect sendfile to work and not semi-randomly block threads indefinitely. Cheers,