runtime/race: support core dumps in race mode

[patricksuo]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   go version go1.7beta1 linux/amd64
2. What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/supei/project/jx3m/Server/go"
GORACE=""
GOROOT="/home/supei/goroot"
GOTOOLDIR="/home/supei/goroot/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build144261612=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

1. What did you do?
   get or set resource limit via system call.

https://play.golang.org/p/ZEsI1Xxyqi

1. What did you expect to see?
   same core size limit
2. What did you see instead?

without -race 
rlimit core: 0 18446744073709551615
with
rlimit core: 0 0

[davecheney]

What is the output you get under the race detector.

On Thu, Jul 28, 2016 at 11:23 PM, su21 notifications@github.com wrote:

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?
go version go1.7beta1 linux/amd64
2.

What operating system and processor architecture are you using (go env
)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/supei/project/jx3m/Server/go"
GORACE=""
GOROOT="/home/supei/goroot"
GOTOOLDIR="/home/supei/goroot/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build144261612=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

1. What did you do? get and set resource limit via system call.

https://play.golang.org/p/ZEsI1Xxyqi

1. What did you expect to see? get different result with -race

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[patricksuo]

without -race
rlimit core: 0 18446744073709551615

with
rlimit core: 0 0

[patricksuo]

strace.txt
It calls setrlimit somewhere.

0000000000459700 <_ZN11__sanitizer28DisableCoreDumperIfNecessaryEv>:
  459700:       48 8d 05 19 db 0a 00    lea    0xadb19(%rip),%rax        # 507220 <_ZN11__sanitizer21common_flags_dont_useE>
  459707:       80 b8 8b 00 00 00 00    cmpb   $0x0,0x8b(%rax)
  45970e:       75 08                   jne    459718 <_ZN11__sanitizer28DisableCoreDumperIfNecessaryEv+0x18>
  459710:       c3                      retq
  459711:       0f 1f 80 00 00 00 00    nopl   0x0(%rax)
  459718:       48 83 ec 18             sub    $0x18,%rsp
  45971c:       bf 04 00 00 00          mov    $0x4,%edi
  459721:       48 89 e6                mov    %rsp,%rsi
  459724:       48 c7 04 24 00 00 00    movq   $0x0,(%rsp)
  45972b:       00
  45972c:       48 c7 44 24 08 00 00    movq   $0x0,0x8(%rsp)
  459733:       00 00
  459735:       e8 c6 e5 01 00          callq  477d00 <setrlimit@plt>
  45973a:       85 c0                   test   %eax,%eax
  45973c:       75 05                   jne    459743 <_ZN11__sanitizer28DisableCoreDumperIfNecessaryEv+0x43>
  45973e:       48 83 c4 18             add    $0x18,%rsp
  459742:       c3                      retq
  459743:       e8 f0 d4 01 00          callq  476c38 <_ZN11__sanitizerL6setlimEim.part.59>
  459748:       0f 1f 84 00 00 00 00    nopl   0x0(%rax,%rax,1)
  45974f:       00

[quentinmit]

That code comes from the sanitizer library (see https://github.com/llvm-mirror/compiler-rt/blob/929d23ef5045d955ef2c36f2bbdb3dc61eca518f/lib/sanitizer_common/sanitizer_posix_libcdep.cc#L90)

The documentation for that flag says:

Disable core dumping. By default, disable_core=1 on 64-bit to avoid dumping a 16T+ core file. Ignored on OSes that don't dump core by default and for sanitizers that don't reserve lots of virtual memory.

Given that comment, it seems like it would be difficult or impossible to fix this.

[mdempsky]

It looks like Linux 3.4 added a MADV_DONTDUMP flag that can be used to omit memory from core dumps, so compiler-rt could potentially use that to avoid needing to disable core dumps altogether.

[tombergan]

I believe this is WAI. Set GORACE='disable_coredump=0' in your environment if you want coredumps with the race detector:

$ cat https://play.golang.org/p/ZEsI1Xxyqi > main.go
$ go run main.go
rlimit core: 0 18446744073709551615
$ go run -race main.go
rlimit core: 0 0
$ GORACE='disable_coredump=0' go run -race main.go
rlimit core: 0 18446744073709551615

[gopherbot]

CL https://golang.org/cl/31650 mentions this issue.

[gopherbot]

CL https://golang.org/cl/32160 mentions this issue.