Random crashes with memory corruption symptoms
harendra.kumar at gmail.com
Mon Feb 3 07:01:30 UTC 2020
Unfortunately, it is present in 8.8.2 as well.
On Mon, 3 Feb 2020 at 11:22, Ömer Sinan Ağacan <omeragacan at gmail.com> wrote:
> You should try with 8.8.2 which fixes a bug in the compacting GC (#17088).
> When debugging it's a good idea to use the latest minor release of your GHC
> version (8.8.2 in your case), as minor releases fix bugs and usually do not
> introduce new ones as they don't ship new features.
> If the problem still exists, unless you're interested in GHC hacking I
> most productive use of the time would be to make the reproduer smaller, and
> collect as many data as possible, like which flags trigger/hide the bug.
> Some of the things you could check:
> - Build your program with `-dcore-lint -dstg-lint -dcmm-lint` and see if it
> - Build your program with `-debug` and run it, see if it crahes.
> - Build your program with `-debug` and run it with `+RTS -DS` and see if
> error message changes.
> But really you should try with 8.8.2 as first thing. It's possible that
> this is
> another manifestation of #17088.
> Harendra Kumar <harendra.kumar at gmail.com>, 3 Şub 2020 Pzt, 01:26
> tarihinde şunu yazdı:
> > Hi,
> > While running a test-suite for the streaming library streamly I am
> encountering a crash which seems to happen at random places at different
> times. The common messages are:
> > * Segmentation fault: 11
> > * internal error: scavenge_mark_stack: unimplemented/strange closure
> type 24792696 @ 0x4200a623e0
> > * internal error: update_fwd: unknown/strange object 223743520
> > and several other such messages. Prima facie this looks like the memory
> is getting corrupted/scribbled somehow. My first suspicion was that this
> could be a problem in the streamly library code. But I have stripped down
> the code to bare minimum and there is no C FFI code or no poking to memory
> > My next suspicion was the hspec/quickcheck testing code that is being
> used in this test. I checked the hspec code to ensure that there is no C
> code/pointer poking in any of the code involved. But no luck there as well,
> still looking to further strip down that code.
> > My suspicion now is moving more towards the GHC RTS. This issue only
> shows when the following conditions are met:
> > * hspec "parallel" combinator is used to run tests in parallel
> > * streamly concurrent code is being tested which can create many threads
> > * The GHC heap size is restricted to a small size ~32MB using "-M32M"
> rts option.
> > * It is consistently seen with GHC 8.6.5 as well as GHC 8.8.1
> > It never occurs when the heap size is not restricted. I have seen random
> crashes before as well with a "IO manager die" message, when using
> concurrent networking IO with streamly. Though earlier it was not easily
> reproducible, I stopped chasing it. But now it looks like that issue might
> also be a manifestation of the same underlying problem.
> > My guess is it could be something in the RTS concurrency/threading
> related code. Let me know if the symptoms ring a bell or if you can point
> to something specific based on the symptoms. Also, what are the usual
> tools/methods/debugging aids/flags to debug such issues in GHC? If not a
> GHC issue what are the possible ways in which such problem can be induced
> by application code?
> > Meanwhile, I am also trying to simplify the reproducing code further to
> remove other factors as much as possible. The current code is at
> https://github.com/composewell/streamly on the ghc-segfault branch. Run
> "$ while true; do cabal run properties || break; done" in the shell and if
> you are lucky it may crash soon. The test code is in "test/Prop.hs" - here
> https://github.com/composewell/streamly/blob/ghc-segfault/test/Prop.hs .
> > -harendra
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