segfault in RTS - can anyone help me tracking this bug down?

Thu May 29 15:27:32 UTC 2014

Oops last time I checked I hadn't cherry-picked the #9078 fix. Retested
with that and it still segfaults.

Unfortunately we haven't found a smaller test case yet. We've been using
Vagrant for repeatable test runs for GHCJS in the past. Would a Vagrant
script for reproducing the crash be ok?

luite

On Thu, May 29, 2014 at 10:19 AM, Simon Marlow <marlowsd at gmail.com> wrote:

> Please record the repro steps exactly, including the git hashes of any
> repositories that you use.  If it is a GC bug, the last thing we want is
> for it to disappear, because then we lose the opportunity to find it.
>
> If you could put the build steps into a script that we can run to
> reproduce the error, that will help too.  And as Edward says, if there's
> any way you can find to reduce the test case so that it still fails, that's
> really useful.
>
> Cheers,
> Simon
>
>
> On 28/05/2014 11:04, Ömer Sinan Ağacan wrote:
>
>> Hi all,
>>
>> I'm suffering from a RTS bug(probably GC related) that makes making
>> progress in my GSoC project impossible. I have very limited knowledge
>> of GHC internals and I currently have no idea how to produce a minimal
>> program that demonstrates the bug. I wrote how to reproduce it and gdb
>> backtrace when segfault happens in a short blog post:
>> http://osa1.net/posts/2014-05-27-worst-bug.html . As also written in
>> the blog post, changing generation count of generational GC will makes
>> the bug disappear in some cases, but it's not a solution.
>>
>> I also pasted backtrace output below for those who don't want to click
>> links.
>>
>> GHC version used is 7.8.2.
>>
>> If anyone give me some pointers to understand what's going wrong or
>> how can I produce a simple program that demonstrates the bug, I'd like
>> to work on that. I'm basically stuck and I can't make any progress
>> with this bug.
>>
>> Thanks,
>> Ömer
>>
>> [  5 of 202] Compiling GHC.Unicode[boot] ( GHC/Unicode.hs-boot,
>> dist/build/GHC/Unicode.js_p_o-boot )
>> Detaching after fork from child process 3382.
>> [  6 of 202] Compiling GHC.IO[boot]     ( GHC/IO.hs-boot,
>> dist/build/GHC/IO.js_p_o-boot )
>> Detaching after fork from child process 3383.
>> [  7 of 202] Compiling GHC.Exception[boot] ( GHC/Exception.lhs-boot,
>> dist/build/GHC/Exception.js_p_o-boot )
>> Detaching after fork from child process 3384.
>> [ 51 of 202] Compiling GHC.Fingerprint[boot] (
>> GHC/Fingerprint.hs-boot, dist/build/GHC/Fingerprint.js_p_o-boot )
>> Detaching after fork from child process 3385.
>> [ 55 of 202] Compiling GHC.IO.Exception[boot] (
>> GHC/IO/Exception.hs-boot, dist/build/GHC/IO/Exception.js_p_o-boot )
>> Detaching after fork from child process 3386.
>> [ 75 of 202] Compiling Foreign.C.Types  ( Foreign/C/Types.hs,
>> dist/build/Foreign/C/Types.js_p_o )
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x000000000425d5c4 in LOOKS_LIKE_CLOSURE_PTR (p=0x0) at
>> includes/rts/storage/ClosureMacros.h:258
>> 258     includes/rts/storage/ClosureMacros.h: No such file or directory.
>> (gdb) bt
>> #0  0x000000000425d5c4 in LOOKS_LIKE_CLOSURE_PTR (p=0x0) at
>> includes/rts/storage/ClosureMacros.h:258
>> #1  0x000000000425f776 in scavenge_mutable_list1 (bd=0x7fffe5c02a00,
>> gen=0x4d1fd48) at rts/sm/Scav.c:1400
>> #2  0x000000000425fa13 in scavenge_capability_mut_Lists1
>> (cap=0x4cfe5c0 <MainCapability>) at rts/sm/Scav.c:1493
>> #3  0x0000000004256b66 in GarbageCollect (collect_gen=0,
>> do_heap_census=rtsFalse, gc_type=2,
>>      cap=0x4cfe5c0 <MainCapability>) at rts/sm/GC.c:342
>> #4  0x00000000042454a3 in scheduleDoGC (pcap=0x7fffffffc198,
>> task=0x4d32b60, force_major=rtsFalse)
>>      at rts/Schedule.c:1650
>> #5  0x0000000004243de4 in schedule (initialCapability=0x4cfe5c0
>> <MainCapability>, task=0x4d32b60)
>>      at rts/Schedule.c:553
>> #6  0x0000000004246436 in scheduleWaitThread (tso=0x7ffff6708d60,
>> ret=0x0, pcap=0x7fffffffc2c0) at rts/Schedule.c:2346
>> #7  0x000000000423e9b4 in rts_evalLazyIO (cap=0x7fffffffc2c0,
>> p=0x477f850, ret=0x0) at rts/RtsAPI.c:500
>> #8  0x0000000004241666 in real_main () at rts/RtsMain.c:63
>> #9  0x0000000004241759 in hs_main (argc=237, argv=0x7fffffffc448,
>> main_closure=0x477f850, rts_config=...)
>>      at rts/RtsMain.c:114
>> #10 0x0000000000408ea7 in main ()
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