runtime/race: sigsegv when using cgo callbacks with the race detector enabled

[Thinkofname]

Only tested on linux/amd64. A simple way to reproduce this is to run the tests in misc/cgo/test
with the race detector enabled. It should crash as follows:

~/go/misc/cgo/test • GOTRACEBACK=2 go test -v -race
fatal error: unexpected signal during runtime execution
[signal 0xb code=0x1 addr=0x0 pc=0x415885]

runtime stack:
runtime.throw(0x769db0, 0x2a)
    /home/matt/go/src/runtime/panic.go:527 +0x96 fp=0x7ffff9f37c10 sp=0x7ffff9f37bf8
runtime.sigpanic()
    /home/matt/go/src/runtime/sigpanic_unix.go:12 +0x5d fp=0x7ffff9f37c60 sp=0x7ffff9f37c10

goroutine 1 [syscall, locked to thread]:
runtime.cgocall_errno(0x4317f0, 0xc20804bef8, 0x0)
    /home/matt/go/src/runtime/cgocall.go:125 +0xc5 fp=0xc20804bed8 sp=0xc20804beb0
_/home/matt/go/misc/cgo/test._Cfunc_lockOSThreadC()
    ??:0 +0x56 fp=0xc20804bef8 sp=0xc20804bed8
_/home/matt/go/misc/cgo/test.init.1()
    /home/matt/go/misc/cgo/test/issue3775.go:23 +0x2d fp=0xc20804bf08 sp=0xc20804bef8
_/home/matt/go/misc/cgo/test.init()
    _/home/matt/go/misc/cgo/test/_test/_obj_test/_cgo_import.go:1 +0x1859 fp=0xc20804bf88 sp=0xc20804bf08
main.init()
    _/home/matt/go/misc/cgo/test/_test/_testmain.go:172 +0x9c fp=0xc20804bf98 sp=0xc20804bf88
runtime.main()
    /home/matt/go/src/runtime/proc.go:100 +0x220 fp=0xc20804bfe0 sp=0xc20804bf98
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc20804bfe8 sp=0xc20804bfe0

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc20803afe8 sp=0xc20803afe0

goroutine 2 [runnable]:
runtime.forcegchelper()
    /home/matt/go/src/runtime/proc.go:144 fp=0xc2080267e0 sp=0xc2080267d8
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc2080267e8 sp=0xc2080267e0
created by runtime.init.4
    /home/matt/go/src/runtime/proc.go:141 +0x32

goroutine 3 [GC sweep wait]:
runtime.gopark(0x78d008, 0x140b740, 0x719b50, 0xd, 0x44df14, 0x1)
    /home/matt/go/src/runtime/proc.go:185 +0x123 fp=0xc208026f68 sp=0xc208026f38
runtime.goparkunlock(0x140b740, 0x719b50, 0xd, 0x14, 0x1)
    /home/matt/go/src/runtime/proc.go:191 +0x5b fp=0xc208026fa0 sp=0xc208026f68
runtime.bgsweep(0xc208056000)
    /home/matt/go/src/runtime/mgcsweep.go:51 +0xba fp=0xc208026fd8 sp=0xc208026fa0
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc208026fe0 sp=0xc208026fd8
created by runtime.gcenable
    /home/matt/go/src/runtime/mgc.go:171 +0x5a

goroutine 4 [runnable]:
runtime.runfinq()
    /home/matt/go/src/runtime/mfinal.go:140 fp=0xc2080277e0 sp=0xc2080277d8
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc2080277e8 sp=0xc2080277e0
created by runtime.createfing
    /home/matt/go/src/runtime/mfinal.go:135 +0x67

goroutine 5 [runnable]:
os/signal.loop()
    /home/matt/go/src/os/signal/signal_unix.go:20 fp=0xc208027fe0 sp=0xc208027fd8
runtime.goexit()
    /home/matt/go/src/runtime/asm_amd64.s:1670 +0x1 fp=0xc208027fe8 sp=0xc208027fe0
created by os/signal.init.1
    /home/matt/go/src/os/signal/signal_unix.go:28 +0x4c
exit status 2
FAIL    _/home/matt/go/misc/cgo/test    0.008s

The common thing between the failing test and the issue with my own code seems to be callbacks from cgo into go

[ianlancetaylor]

CC @dvyukov

I don't think we can reliably use the race detector in a cgo program, but it would be nicer if we didn't crash.

[rsc]

This is a regression since 1.4.

[gopherbot]

CL https://golang.org/cl/12534 mentions this issue.