testing: benchmark ReportMetric panic on concurrent call

[Jack-Kingdom]

What version of Go are you using (go version)?

$ go version
go version go1.18.4 darwin/amd64

Does this issue reproduce with the latest release?

yes

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

go env Output

$ go env
GO111MODULE="auto"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/jack/Library/Caches/go-build"
GOENV="/Users/jack/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/jack/.go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/jack/.go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.18.4/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.18.4/libexec/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.18.4"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/zv/mhvsb81s63b7kk08sfhfq8d00000gn/T/go-build1807741596=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

example code: https://go.dev/play/p/ToeyneuJPcT

What did you expect to see?

no panic here

[Jack-Kingdom]

Copy panic log here

fatal error: concurrent map writes
fatal error: concurrent map writes

goroutine 1200 [running]:
runtime.throw({0x4ae646?, 0x0?})
	/usr/local/go-faketime/src/runtime/panic.go:992 +0x71 fp=0xc0001de740 sp=0xc0001de710 pc=0x431e91
runtime.mapassign_faststr(0x4ab755?, 0x2?, {0x4ab755, 0x2})
	/usr/local/go-faketime/src/runtime/map_faststr.go:212 +0x39c fp=0xc0001de7a8 sp=0xc0001de740 pc=0x4114bc
testing.(*B).ReportMetric(...)
	/usr/local/go-faketime/src/testing/benchmark.go:356
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:7 +0x65 fp=0xc0001de7e0 sp=0xc0001de7a8 pc=0x48e665
runtime.goexit()
	/usr/local/go-faketime/src/runtime/asm_amd64.s:1571 +0x1 fp=0xc0001de7e8 sp=0xc0001de7e0 pc=0x45cdc1
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1 [chan receive]:
testing.(*B).doBench(0xc0000c4000)
	/usr/local/go-faketime/src/testing/benchmark.go:285 +0x7f
testing.(*B).run(0xc0000c4000?)
	/usr/local/go-faketime/src/testing/benchmark.go:279 +0x6e
testing.Benchmark(0x4b3f48)
	/usr/local/go-faketime/src/testing/benchmark.go:824 +0xf5
main.main()
	/tmp/sandbox1758758439/prog.go:18 +0x25

goroutine 59 [runnable]:
main.BenchmarkReportMetrics(0xc0000c4000)
	/tmp/sandbox1758758439/prog.go:12 +0x87
testing.(*B).runN(0xc0000c4000, 0x2710)
	/usr/local/go-faketime/src/testing/benchmark.go:193 +0x102
testing.(*B).launch(0xc0000c4000)
	/usr/local/go-faketime/src/testing/benchmark.go:334 +0x1c5
created by testing.(*B).doBench
	/usr/local/go-faketime/src/testing/benchmark.go:284 +0x6c

goroutine 1393 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1391 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1394 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1277 [running]:
	goroutine running on other thread; stack unavailable
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1392 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1396 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1395 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1389 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1388 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1387 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1386 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1390 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1385 [runnable]:
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:6
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

goroutine 1277 [running]:
runtime.throw({0x4ae646?, 0x0?})
	/usr/local/go-faketime/src/runtime/panic.go:992 +0x71 fp=0xc000186f40 sp=0xc000186f10 pc=0x431e91
runtime.mapassign_faststr(0x49a6e0, 0xc000012030, {0x4ab755, 0x2})
	/usr/local/go-faketime/src/runtime/map_faststr.go:295 +0x38b fp=0xc000186fa8 sp=0xc000186f40 pc=0x4114ab
testing.(*B).ReportMetric(...)
	/usr/local/go-faketime/src/testing/benchmark.go:356
main.BenchmarkReportMetrics.func1()
	/tmp/sandbox1758758439/prog.go:7 +0x65 fp=0xc000186fe0 sp=0xc000186fa8 pc=0x48e665
runtime.goexit()
	/usr/local/go-faketime/src/runtime/asm_amd64.s:1571 +0x1 fp=0xc000186fe8 sp=0xc000186fe0 pc=0x45cdc1
created by main.BenchmarkReportMetrics
	/tmp/sandbox1758758439/prog.go:12 +0x87

Program exited.

[Jack-Kingdom]

try aquire lock on benchmark extra map write
#54038

[seankhliao]

This looks like an incorrect use of ReportMetric though

[bcmills]

This looks like an incorrect use of ReportMetric though

I agree, especially given this sentence in its documentation:

ReportMetric overrides any previously reported value for the same unit.

Without a happens-before relationship between the calls to ReportMetric, the notion of “previously reported” is not well defined.

By convention, Go methods that mutate the state of a data-structure (as ReportMetric does) should be considered unsafe for concurrent use unless the documentation explicitly says otherwise.