GC errors when time benchmarks are run with GOMAXPROCS > 1

[gopherbot]

by consalus:

Using 6g on darwin at 0c8b700cc391+ tip, when I run
"make bench" in src/pkg/time/ with GOMAXPROCS > 1, I get various errors when
BenchmarkStop runs. It doesn't happen every time, but most of the time.

The stack trace varies a bit. Here is one example:

time_test.BenchmarkAfterFunc      100000         16142 ns/op
time_test.BenchmarkAfter      100000         18120 ns/op
panic: invalid memory address or nil pointer dereference
throw: panic during gc

[signal 0xb code=0x1 addr=0x0 pc=0x97c6]

runtime.throw+0x3b /Users/username/code/go/src/pkg/runtime/runtime.c:78
    runtime.throw(0x1538c8, 0x153c47)
runtime.panicstring+0x51 /Users/username/code/go/src/pkg/runtime/runtime.c:89
    runtime.panicstring(0x153c47, 0x0)
runtime.sigpanic+0x144 /Users/username/code/go/src/pkg/runtime/darwin/thread.c:469
    runtime.sigpanic()
ReleaseN+0x30 /Users/username/code/go/src/pkg/runtime/mcache.c:64
    ReleaseN(0x2170000, 0x2170030, 0x3000000e0, 0xf83fffff00, 0xf840147d08, ...)
runtime.MCache_ReleaseAll+0x53 /Users/username/code/go/src/pkg/runtime/mcache.c:128
    runtime.MCache_ReleaseAll(0x2170000, 0xe9db)
stealcache+0x3a /Users/username/code/go/src/pkg/runtime/mgc0.c:500
    stealcache()
runtime.gc+0x1ca /Users/username/code/go/src/pkg/runtime/mgc0.c:577
    runtime.gc(0xf800000001, 0xf840000dc0)
runfinq+0x112 /Users/username/code/go/src/pkg/runtime/mgc0.c:657
    runfinq()
runtime.goexit /Users/username/code/go/src/pkg/runtime/proc.c:149
    runtime.goexit()

goroutine 330315 [3]:
runtime.entersyscall+0x28 /Users/username/code/go/src/pkg/runtime/proc.c:577
    runtime.entersyscall()
syscall.Syscall6+0x5 /Users/username/code/go/src/pkg/syscall/asm_darwin_amd64.s:38
    syscall.Syscall6()
syscall.Select+0x66 /Users/username/code/go/src/pkg/syscall/zsyscall_darwin_amd64.go:704
    syscall.Select(0x0, 0x0, 0x0, 0x0, 0xf84001bfc0, ...)
syscall.Sleep+0x7a /Users/username/code/go/src/pkg/syscall/syscall_bsd.go:145
    syscall.Sleep(0x3b90b3f8, 0xf84001bf00, 0x7b420, 0xf8400cd040)
time.sleeper+0xa9 /Users/username/code/go/src/pkg/time/sleep.go:154
    time.sleeper(0x35c30, 0x0)
runtime.goexit /Users/username/code/go/src/pkg/runtime/proc.c:149
    runtime.goexit()
fmt.*pp·fmtUint64+0x137 /Users/username/code/go/src/pkg/fmt/print.go:384
    fmt.*pp·fmtUint64(0x0, 0x0, 0x0, 0x0, 0x0, ...)

goroutine 1 [1]:
runtime.gosched+0x77 /Users/username/code/go/src/pkg/runtime/proc.c:558
    runtime.gosched()
runtime.exitsyscall+0xa2 /Users/username/code/go/src/pkg/runtime/proc.c:624
    runtime.exitsyscall()
syscall.Syscall+0x61 /Users/username/code/go/src/pkg/syscall/asm_darwin_amd64.s:34
    syscall.Syscall()
syscall.gettimeofday+0x45
/Users/username/code/go/src/pkg/syscall/zsyscall_darwin_amd64.go:922
    syscall.gettimeofday(0xf840121a60, 0x29, 0x9279, 0x10, 0x40, ...)
syscall.Gettimeofday+0x27
/Users/username/code/go/src/pkg/syscall/syscall_darwin_amd64.go:31
    syscall.Gettimeofday(0xf840121a60, 0xf840121a60, 0x10, 0xf840099e40)
os.Time+0x4e /Users/username/code/go/src/pkg/os/time.go:16
    os.Time(0xf840099e40, 0x100000000, 0x0, 0x0, 0x500002ea1, ...)
time.Nanoseconds+0x1c /Users/username/code/go/src/pkg/time/time.go:26
    time.Nanoseconds(0x400000003, 0x4deb)
time.after+0x1f /Users/username/code/go/src/pkg/time/sleep.go:119
    time.after(0x3b9aca00, 0xf840099e40, 0xf840000958, 0xf840099e40, 0xf840000958, ...)
time.NewTimer+0x83 /Users/username/code/go/src/pkg/time/sleep.go:78
    time.NewTimer(0x3b9aca00, 0xf8400d7001, 0x4a9344f55ee00, 0x19456)
/Users/username/code/go/src/pkg/time/_xtest_.BenchmarkStop+0x36
/Users/username/code/go/src/pkg/time/sleep_test.go:75
    /Users/username/code/go/src/pkg/time/_xtest_.BenchmarkStop(0xf840099d80, 0x19669)
testing.*B·runN+0x48 /Users/username/code/go/src/pkg/testing/benchmark.go:72
    testing.*B·runN(0xf840099d80, 0x7a120, 0x1, 0x7a12000002710)
testing.*B·run+0xda /Users/username/code/go/src/pkg/testing/benchmark.go:141
    testing.*B·run(0xf840099d80, 0xf840099d80, 0x6ae30, 0x17)
testing.RunBenchmarks+0x1d5 /Users/username/code/go/src/pkg/testing/benchmark.go:199
    testing.RunBenchmarks(0x1e40b, 0xf8400323c0, 0x800000008, 0x2a86)
main.main+0x7b /Users/username/code/go/src/pkg/time/_testmain.go:41
    main.main()
runtime.mainstart+0xf /Users/username/code/go/src/pkg/runtime/amd64/asm.s:77
    runtime.mainstart()
runtime.goexit /Users/username/code/go/src/pkg/runtime/proc.c:149
    runtime.goexit()
make: *** [bench] Error 2


Here is another stack trace:

time_test.BenchmarkAfterFunc      100000         16283 ns/op
time_test.BenchmarkAfter      100000         18473 ns/op
panic: runtime error: invalid memory address or nil pointer dereference

[signal 0xb code=0x1 addr=0x54 pc=0x13b8f]

runtime.panic+0xa7 /Users/username/code/go/src/pkg/runtime/proc.c:1023
    runtime.panic(0x77284, 0xf8400f7c20)
runtime.panicstring+0xa3 /Users/username/code/go/src/pkg/runtime/runtime.c:92
    runtime.panicstring(0x153c47, 0x2170400)
runtime.sigpanic+0x144 /Users/username/code/go/src/pkg/runtime/darwin/thread.c:469
    runtime.sigpanic()
runtime.destroylock+0x1c /Users/username/code/go/src/pkg/runtime/darwin/thread.c:85
    runtime.destroylock(0x50, 0xf840097c40)
destroychan+0x29 /Users/username/code/go/src/pkg/runtime/chan.c:140
    destroychan(0x0, 0xf840009500)
----- stack segment boundary -----
runfinq+0xc3 /Users/username/code/go/src/pkg/runtime/mgc0.c:650
    runfinq()
runtime.goexit /Users/username/code/go/src/pkg/runtime/proc.c:149
    runtime.goexit()

goroutine 330314 [3]:
runtime.entersyscall+0x28 /Users/username/code/go/src/pkg/runtime/proc.c:577
    runtime.entersyscall()
syscall.Syscall6+0x5 /Users/username/code/go/src/pkg/syscall/asm_darwin_amd64.s:38
    syscall.Syscall6()
syscall.Select+0x66 /Users/username/code/go/src/pkg/syscall/zsyscall_darwin_amd64.go:704
    syscall.Select(0x0, 0x0, 0x0, 0x0, 0xf8400e8f00, ...)
syscall.Sleep+0x7a /Users/username/code/go/src/pkg/syscall/syscall_bsd.go:145
    syscall.Sleep(0x3b95c0f0, 0xf8400e8ee0, 0x7b398, 0xf840097300)
time.sleeper+0xa9 /Users/username/code/go/src/pkg/time/sleep.go:154
    time.sleeper(0x35c2f, 0x0)
runtime.goexit /Users/username/code/go/src/pkg/runtime/proc.c:149
    runtime.goexit()
fmt.*pp·fmtUint64+0xe4 /Users/username/code/go/src/pkg/fmt/print.go:395
    fmt.*pp·fmtUint64(0x0, 0x0, 0x0, 0x0, 0x0, ...)

goroutine 1 [3]:
runtime.entersyscall+0x28 /Users/username/code/go/src/pkg/runtime/proc.c:577
    runtime.entersyscall()
syscall.Syscall+0x5 /Users/username/code/go/src/pkg/syscall/asm_darwin_amd64.s:14
    syscall.Syscall()
syscall.gettimeofday+0x45
/Users/username/code/go/src/pkg/syscall/zsyscall_darwin_amd64.go:922
    syscall.gettimeofday(0x400000003, 0xf8400d0000, 0x9279, 0x10, 0x155088, ...)
syscall.Gettimeofday+0x27
/Users/username/code/go/src/pkg/syscall/syscall_darwin_amd64.go:31
    syscall.Gettimeofday(0x2000000008, 0xf8400e8ac0, 0xf800000001, 0x2cd88)
runtime.mal+0x3f /Users/username/code/go/src/pkg/runtime/malloc.c:285
    runtime.mal(0xf8400abd70, 0x8a86)
make: *** [bench] Error 2

[rsc]

Comment 1:

Reproduced very quickly on my machine.
Excellent test case, thanks very much.

Owner changed to r...@golang.org.

Status changed to Accepted.

[alberts]

Comment 2:

I think this is the same problem as I mentioned in issue #1479. We were running the
TestHilbert function with GOMAXPROCS>1 too.

[rsc]

Comment 3:

This issue was closed by revision 2509776.

Status changed to Fixed.