Segfault when using SharedArray on OS X

[jdrugo]

When working on an parallel implementation of a particle filter, Julia started segfault'ing under heavy workload. A minimal example to reproduce this behavior is

@everywhere begin
    type A
        x::SharedArray{Float64,1}
        A(N) = new(SharedArray(Float64, N))
    end
    localf(x::SharedArray) = nothing
    function f(a::A)
        map(fetch, Any[(@spawnat i localf(a.x)) for i in workers()])
    end
end


a = A(1000)
for n = 1:10^8
    f(a)
end

This results on my MacBook Pro under OS X El Capitan in

Jans-MacBook-Pro:~ jdrugo$ /Applications/Julia-0.4.1.app/Contents/Resources/julia/bin/julia -p 7 ./crash_example.jl

signal (11): Segmentation fault: 11
__pool_alloc at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/gc.c:1053
_new_array_ at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/array.c:84
_new_array at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/array.c:333
call at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
def_rv_channel at multi.jl:619
jlcall_def_rv_channel_21329 at  (unknown line)
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
lookup_ref at multi.jl:513
remotecall_fetch at multi.jl:727
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
call_on_owner at multi.jl:778
fetch at multi.jl:796
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
map at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
f at /Users/jdrugo/crash_example.jl:9
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
anonymous at /Users/jdrugo/crash_example.jl:15
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
jl_parse_eval_all at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/toplevel.c:577
jl_load at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/toplevel.c:620
include at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
include_from_node1 at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
process_options at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
_start at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
jlcall__start_18614 at /Applications/Julia-0.4.1.app/Contents/Resources/julia/lib/julia/sys.dylib (unknown line)
jl_apply at /Users/osx/buildbot/slave/package_osx10_9-x64/build/src/./julia.h:1325
true_main at /Applications/Julia-0.4.1.app/Contents/Resources/julia/bin/julia (unknown line)
main at /Applications/Julia-0.4.1.app/Contents/Resources/julia/bin/julia (unknown line)
Segmentation fault: 11

Julia version:

julia> versioninfo()
Julia Version 0.4.1
Commit cbe1bee* (2015-11-08 10:33 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin13.4.0)
  CPU: Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.3

[sbromberger]

I can reproduce this on my system as well:

julia> versioninfo()
Julia Version 0.4.2-pre+18
Commit eb31eef (2015-11-26 08:03 UTC)
Platform Info:
  System: Darwin (x86_64-apple-darwin15.0.0)
  CPU: Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-svn

[amitmurthy]

On 0.4.2 without any workers :

ERROR: UndefRefError: access to undefined reference
 in ht_keyindex2 at dict.jl:602
 in setindex! at dict.jl:643
 in schedule_call at multi.jl:660
 in remotecall at multi.jl:703
 in f at none:8
 [inlined code] from none:2
 in anonymous at no file:0

On 0.4.2 with 2 workers :

fatal error on 2: ERROR: BoundsError: attempt to access 0-element Array{Any,1}
  at index [2]
 in notify at /Volumes/Julia/Julia-0.4.2.app/Contents/Resources/julia/lib/julia/sys.dylib
 in __notify#32__ at /Volumes/Julia/Julia-0.4.2.app/Contents/Resources/julia/lib/julia/sys.dylib
 in send_add_client at multi.jl:592
 in serialize at serialize.jl:185
 in serialize at sharedarray.jl:269
 in serialize_any at serialize.jl:422
 in serialize at serialize.jl:405
 in serialize at serialize.jl:127
 in serialize at serialize.jl:310
 in serialize_any at serialize.jl:422
 in send_msg_ at multi.jl:222
 in remotecall at multi.jl:710
 in f at none:8
 [inlined code] from none:2
 in anonymous at no file:0

Works fine on 0.5 with 2 workers.

On 0.5 with no workers I see a series of

error in running finalizer: UndefRefError()
error in running finalizer: UndefRefError()
error in running finalizer: UndefRefError()

I suspect a memory corruption in the shared memory code. And could possibly be the same issue as #14186 (comment)

[amitmurthy]

Reduced case with no workers on 0.5:

for n = 1:10^8
   map(fetch, Any[(@spawnat i i) for i in workers()])
end

No error when run with workers added. Errors out on 0.4 .

[tkelman]

Is this closed on master by #14456?

[amitmurthy]

Yes.

[amitmurthy]

Why did you close it? The bug reported was for 0.4 and that will be open till 0.4.3 is released.

[tkelman]

Generally issues should be closed by fixes getting merged to master, unless it's an issue that was never a problem for master.