[Qemu-devel] [Bug 1763536] Re: go build fails under qemu-ppc64le-static (qemu-user)

[David Wilder <1763536@bugs.launchpad.net>]

I missed a step for reproduction.  Step 1 should be:
docker run --rm --privileged multiarch/qemu-user-static:register
This modprobes binfmt and registers qemu-ppc64le-static as the interpreter for ppc64le executables.

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https://bugs.launchpad.net/bugs/1763536

Title:
  go build fails under qemu-ppc64le-static (qemu-user)

Status in QEMU:
  New

Bug description:
  I am using qemu-user (built static) in a docker container environment.
  When running multi-threaded go commands in the container (go build for
  example) the process may hang, report segfaults or other errors.  I
  built qemu-ppc64le from the upstream git (master).

  I see the problem running on a multi core system with Intel i7 processors.
  # cat /proc/cpuinfo | grep "model name"
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz
  model name	: Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz

  Steps to reproduce:
  1) Build qemu-ppc64le as static and copy into docker build directory named it qemu-ppc64le-static.

  2) Add hello.go to docker build dir.

  package main
  import "fmt"
  func main() {
  	fmt.Println("hello world")
  }

  3) Create the Dockerfile from below:

  FROM ppc64le/golang:1.10.1-alpine3.
  COPY qemu-ppc64le-static /usr/bin/
  COPY hello.go /go

  4) Build container
  $ docker build -t qemutest -f Dockerfile ./go 

  5) Run test
  $ docker run -it qemutest

  /go # /usr/bin/qemu-ppc64le-static --version
  qemu-ppc64le version 2.11.93 (v2.12.0-rc3-dirty)
  Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers

  /go # go version
  go version go1.10.1 linux/ppc64le

  /go # go build hello.go
  fatal error: fatal error: stopm holding locksunexpected signal during runtime execution

  panic during panic
  [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1003528c]

  runtime stack:
  runtime: unexpected return pc for syscall.Syscall6 called from 0xc42007f500
  stack: frame={sp:0xc4203be840, fp:0xc4203be860} stack=[0x4000b7ecf0,0x4000b928f0)

  syscall.Syscall6(0x100744e8, 0x3d, 0xc42050c140, 0x20, 0x18, 0x10422b80, 0xc4203be968[signal , 0x10012d88SIGSEGV: segmentation violation, 0xc420594000 code=, 0x00x1 addr=0x0 pc=0x1003528c)
  ]

  runtime stack:
  	/usr/local/go/src/syscall/asm_linux_ppc64x.s:61runtime.throw(0x10472d19, 0x13)
   +	/usr/local/go/src/runtime/panic.go:0x6c616 +0x68

  
  runtime.stopm()
  	/usr/local/go/src/runtime/proc.go:1939goroutine  +10x158
   [runtime.exitsyscall0semacquire(0xc42007f500)
  	/usr/local/go/src/runtime/proc.go:3129 +]:
  0x130
  runtime.mcall(0xc42007f500)
  	/usr/local/go/src/runtime/asm_ppc64x.s:183 +0x58sync.runtime_Semacquire
  (0xc4201fab1c)
  	/usr/local/go/src/runtime/sema.go:56 +0x38

  ----
  Note the results may differ between attempts,  hangs and other faults sometimes happen.
  ----
  If I run "go: single threaded I don't see the problem, for example:

  /go # GOMAXPROCS=1 go build -p 1 hello.go 
  /go # ./hello
  hello world

  I see the same issue with arm64.  I don't think this is a go issue,
  but don't have a real evidence to prove that.  This problem looks
  similar to other problem I have seen reported against qemu running
  multi-threaded applications.

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