schedule: re-entered unsafely - with heavy concurrent load
ekarttun at cs.helsinki.fi
Fri Feb 18 17:15:04 EST 2005
I am having problems with the threaded rts (6.5.20050207)
dying with 'schedule: re-entered unsafely'. The same code
seems to work with 6.2.2 with threaded rts.
The exact error message is:
"foo: schedule: re-entered unsafely.
Perhaps a 'foreign import unsafe' should be 'safe'?"
I originally notices the problem with networking code which
didn't use any of Network (nor threadWaitX). However the error
appeared even with the standard libraries tipping in the direction
of a bug in the rts.
The code works most of the time, but has a small probability of
failing when load is high. The test case implements a dummy web
server which can be tried with e.g. apache benchmark (ab),
/usr/sbin/ab2 -c 1000 -n 5000 127.0.0.1:8080/foo
usually crashes the code when run a few times.
The code should be compiled and run as
ghc --make -threaded foo.hs -o foo && ./foo 8080
import qualified Control.Exception as E
main = do [port] <- getArgs
server port = do
s <- listenOn $ PortNumber $ fromIntegral $ read port
acceptLoop sock = do
(csock,_,_) <- accept sock
forkIO (handle csock `E.catch` print)
handle sock = do
hPutStr sock "HTTP/1.0 200 OK\r\nContent-Type: text/plain\r\n\r\n"
hPutStr sock ("This is the body for the request to\n"++"hope you like this.\n\nnow garbage:\n")
- Einar Karttunen
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