Dear gtk2hs developers,
What's the current state of gtk2hs with respect to the threaded RTS and
C finalizers? Should we expect 0.10.1 to work?
As you may know, we're working on ThreadScope, a gtk2hs-based tool for
parallel performance visualisation in GHC. I recently switched to use
the threaded RTS so that I could do some work while displaying a
progress bar - I know there are ways to do this without -threaded, but I
thought -threaded would be the neatest way to do it, and eventually
we'll want to have background threads doing things anyway.
Now I have weird problems - usually hangs/deadlocks, but occasionally I
get an Xlib error. Here's my latest hang, which is 100% reproducible on
exiting ThreadScope right now:
(gdb) where
#0 0x0000003c0aa0af19 in pthread_cond_wait@@GLIBC_2.3.2 () from
/lib64/libpthread.so.0
#1 0x00000000005b2c0e in waitCondition (pCond=0x1a43918,
pMut=0x1a43948) at posix/OSThreads.c:65
#2 0x00000000005d72d9 in waitForReturnCapability (pCap=0x7ffffe1499f0,
task=0x1a438e0) at Capability.c:445
#3 0x00000000005a5934 in rts_lock () at RtsAPI.c:572
#4 0x00000000004cf247 in SystemziGlibziGObject_d1wV ()
#5 0x0000003c10cd8eed in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#6 0x0000003c0ba0d6a8 in g_object_unref () from /lib64/libgobject-2.0.so.0
.... various stuff omitted ....
#41 0x0000003c0ba0d632 in g_object_unref () from /lib64/libgobject-2.0.so.0
#42 0x00000000005b20fd in runCFinalizer (fn=0x408968, ptr=0x1a69440,
env=0x0, flag=0) at Weak.c:34
#43 0x00000000005b216a in runAllCFinalizers (list=0x2afbacb5f060) at
Weak.c:50
#44 0x00000000005a8077 in hs_exit_ (wait_foreign=rtsFalse) at
RtsStartup.c:413
#45 0x00000000005a81a8 in shutdownHaskellAndExit (n=0) at RtsStartup.c:557
#46 0x00000000005a4c6a in real_main () at Main.c:144
#47 0x00000000005a4ca4 in main (argc=5, argv=0x7ffffe14b338) at Main.c:156
So clearly g_object_unref is being called from a C finalizer, and it
ends up calling back into Haskell via something in System.Glib.Object,
this leads to a deadlock because the RTS is shutting down and can't run
any Haskell code.
Any help appreciated. In the meantime I'll probably go back to the
single-threaded RTS.
Cheers,
Simon
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